| /* |
| * linux/mm/filemap.c |
| * |
| * Copyright (C) 1994-1999 Linus Torvalds |
| */ |
| |
| /* |
| * This file handles the generic file mmap semantics used by |
| * most "normal" filesystems (but you don't /have/ to use this: |
| * the NFS filesystem used to do this differently, for example) |
| */ |
| #include <linux/export.h> |
| #include <linux/compiler.h> |
| #include <linux/dax.h> |
| #include <linux/fs.h> |
| #include <linux/sched/signal.h> |
| #include <linux/uaccess.h> |
| #include <linux/capability.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/gfp.h> |
| #include <linux/mm.h> |
| #include <linux/swap.h> |
| #include <linux/mman.h> |
| #include <linux/pagemap.h> |
| #include <linux/file.h> |
| #include <linux/uio.h> |
| #include <linux/hash.h> |
| #include <linux/writeback.h> |
| #include <linux/backing-dev.h> |
| #include <linux/pagevec.h> |
| #include <linux/blkdev.h> |
| #include <linux/security.h> |
| #include <linux/cpuset.h> |
| #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ |
| #include <linux/hugetlb.h> |
| #include <linux/memcontrol.h> |
| #include <linux/cleancache.h> |
| #include <linux/rmap.h> |
| #include <linux/delayacct.h> |
| #include <linux/psi.h> |
| #include "internal.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/filemap.h> |
| |
| /* |
| * FIXME: remove all knowledge of the buffer layer from the core VM |
| */ |
| #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
| |
| #include <asm/mman.h> |
| |
| /* |
| * Shared mappings implemented 30.11.1994. It's not fully working yet, |
| * though. |
| * |
| * Shared mappings now work. 15.8.1995 Bruno. |
| * |
| * finished 'unifying' the page and buffer cache and SMP-threaded the |
| * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
| * |
| * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
| */ |
| |
| /* |
| * Lock ordering: |
| * |
| * ->i_mmap_rwsem (truncate_pagecache) |
| * ->private_lock (__free_pte->__set_page_dirty_buffers) |
| * ->swap_lock (exclusive_swap_page, others) |
| * ->mapping->tree_lock |
| * |
| * ->i_mutex |
| * ->i_mmap_rwsem (truncate->unmap_mapping_range) |
| * |
| * ->mmap_sem |
| * ->i_mmap_rwsem |
| * ->page_table_lock or pte_lock (various, mainly in memory.c) |
| * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) |
| * |
| * ->mmap_sem |
| * ->lock_page (access_process_vm) |
| * |
| * ->i_mutex (generic_perform_write) |
| * ->mmap_sem (fault_in_pages_readable->do_page_fault) |
| * |
| * bdi->wb.list_lock |
| * sb_lock (fs/fs-writeback.c) |
| * ->mapping->tree_lock (__sync_single_inode) |
| * |
| * ->i_mmap_rwsem |
| * ->anon_vma.lock (vma_adjust) |
| * |
| * ->anon_vma.lock |
| * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
| * |
| * ->page_table_lock or pte_lock |
| * ->swap_lock (try_to_unmap_one) |
| * ->private_lock (try_to_unmap_one) |
| * ->tree_lock (try_to_unmap_one) |
| * ->zone_lru_lock(zone) (follow_page->mark_page_accessed) |
| * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page) |
| * ->private_lock (page_remove_rmap->set_page_dirty) |
| * ->tree_lock (page_remove_rmap->set_page_dirty) |
| * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) |
| * ->inode->i_lock (page_remove_rmap->set_page_dirty) |
| * ->memcg->move_lock (page_remove_rmap->lock_page_memcg) |
| * bdi.wb->list_lock (zap_pte_range->set_page_dirty) |
| * ->inode->i_lock (zap_pte_range->set_page_dirty) |
| * ->private_lock (zap_pte_range->__set_page_dirty_buffers) |
| * |
| * ->i_mmap_rwsem |
| * ->tasklist_lock (memory_failure, collect_procs_ao) |
| */ |
| |
| static int page_cache_tree_insert(struct address_space *mapping, |
| struct page *page, void **shadowp) |
| { |
| struct radix_tree_node *node; |
| void **slot; |
| int error; |
| |
| error = __radix_tree_create(&mapping->page_tree, page->index, 0, |
| &node, &slot); |
| if (error) |
| return error; |
| if (*slot) { |
| void *p; |
| |
| p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock); |
| if (!radix_tree_exceptional_entry(p)) |
| return -EEXIST; |
| |
| mapping->nrexceptional--; |
| if (shadowp) |
| *shadowp = p; |
| } |
| __radix_tree_replace(&mapping->page_tree, node, slot, page, |
| workingset_update_node, mapping); |
| mapping->nrpages++; |
| return 0; |
| } |
| |
| static void page_cache_tree_delete(struct address_space *mapping, |
| struct page *page, void *shadow) |
| { |
| int i, nr; |
| |
| /* hugetlb pages are represented by one entry in the radix tree */ |
| nr = PageHuge(page) ? 1 : hpage_nr_pages(page); |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(PageTail(page), page); |
| VM_BUG_ON_PAGE(nr != 1 && shadow, page); |
| |
| for (i = 0; i < nr; i++) { |
| struct radix_tree_node *node; |
| void **slot; |
| |
| __radix_tree_lookup(&mapping->page_tree, page->index + i, |
| &node, &slot); |
| |
| VM_BUG_ON_PAGE(!node && nr != 1, page); |
| |
| radix_tree_clear_tags(&mapping->page_tree, node, slot); |
| __radix_tree_replace(&mapping->page_tree, node, slot, shadow, |
| workingset_update_node, mapping); |
| } |
| |
| if (shadow) { |
| mapping->nrexceptional += nr; |
| /* |
| * Make sure the nrexceptional update is committed before |
| * the nrpages update so that final truncate racing |
| * with reclaim does not see both counters 0 at the |
| * same time and miss a shadow entry. |
| */ |
| smp_wmb(); |
| } |
| mapping->nrpages -= nr; |
| } |
| |
| /* |
| * Delete a page from the page cache and free it. Caller has to make |
| * sure the page is locked and that nobody else uses it - or that usage |
| * is safe. The caller must hold the mapping's tree_lock. |
| */ |
| void __delete_from_page_cache(struct page *page, void *shadow) |
| { |
| struct address_space *mapping = page->mapping; |
| int nr = hpage_nr_pages(page); |
| |
| trace_mm_filemap_delete_from_page_cache(page); |
| /* |
| * if we're uptodate, flush out into the cleancache, otherwise |
| * invalidate any existing cleancache entries. We can't leave |
| * stale data around in the cleancache once our page is gone |
| */ |
| if (PageUptodate(page) && PageMappedToDisk(page)) |
| cleancache_put_page(page); |
| else |
| cleancache_invalidate_page(mapping, page); |
| |
| VM_BUG_ON_PAGE(PageTail(page), page); |
| VM_BUG_ON_PAGE(page_mapped(page), page); |
| if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) { |
| int mapcount; |
| |
| pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", |
| current->comm, page_to_pfn(page)); |
| dump_page(page, "still mapped when deleted"); |
| dump_stack(); |
| add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
| |
| mapcount = page_mapcount(page); |
| if (mapping_exiting(mapping) && |
| page_count(page) >= mapcount + 2) { |
| /* |
| * All vmas have already been torn down, so it's |
| * a good bet that actually the page is unmapped, |
| * and we'd prefer not to leak it: if we're wrong, |
| * some other bad page check should catch it later. |
| */ |
| page_mapcount_reset(page); |
| page_ref_sub(page, mapcount); |
| } |
| } |
| |
| page_cache_tree_delete(mapping, page, shadow); |
| |
| page->mapping = NULL; |
| /* Leave page->index set: truncation lookup relies upon it */ |
| |
| /* hugetlb pages do not participate in page cache accounting. */ |
| if (PageHuge(page)) |
| return; |
| |
| __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr); |
| if (PageSwapBacked(page)) { |
| __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); |
| if (PageTransHuge(page)) |
| __dec_node_page_state(page, NR_SHMEM_THPS); |
| } else { |
| VM_BUG_ON_PAGE(PageTransHuge(page), page); |
| } |
| |
| /* |
| * At this point page must be either written or cleaned by truncate. |
| * Dirty page here signals a bug and loss of unwritten data. |
| * |
| * This fixes dirty accounting after removing the page entirely but |
| * leaves PageDirty set: it has no effect for truncated page and |
| * anyway will be cleared before returning page into buddy allocator. |
| */ |
| if (WARN_ON_ONCE(PageDirty(page))) |
| account_page_cleaned(page, mapping, inode_to_wb(mapping->host)); |
| } |
| |
| /** |
| * delete_from_page_cache - delete page from page cache |
| * @page: the page which the kernel is trying to remove from page cache |
| * |
| * This must be called only on pages that have been verified to be in the page |
| * cache and locked. It will never put the page into the free list, the caller |
| * has a reference on the page. |
| */ |
| void delete_from_page_cache(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| unsigned long flags; |
| void (*freepage)(struct page *); |
| |
| BUG_ON(!PageLocked(page)); |
| |
| freepage = mapping->a_ops->freepage; |
| |
| spin_lock_irqsave(&mapping->tree_lock, flags); |
| __delete_from_page_cache(page, NULL); |
| spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| |
| if (freepage) |
| freepage(page); |
| |
| if (PageTransHuge(page) && !PageHuge(page)) { |
| page_ref_sub(page, HPAGE_PMD_NR); |
| VM_BUG_ON_PAGE(page_count(page) <= 0, page); |
| } else { |
| put_page(page); |
| } |
| } |
| EXPORT_SYMBOL(delete_from_page_cache); |
| |
| int filemap_check_errors(struct address_space *mapping) |
| { |
| int ret = 0; |
| /* Check for outstanding write errors */ |
| if (test_bit(AS_ENOSPC, &mapping->flags) && |
| test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
| ret = -ENOSPC; |
| if (test_bit(AS_EIO, &mapping->flags) && |
| test_and_clear_bit(AS_EIO, &mapping->flags)) |
| ret = -EIO; |
| return ret; |
| } |
| EXPORT_SYMBOL(filemap_check_errors); |
| |
| static int filemap_check_and_keep_errors(struct address_space *mapping) |
| { |
| /* Check for outstanding write errors */ |
| if (test_bit(AS_EIO, &mapping->flags)) |
| return -EIO; |
| if (test_bit(AS_ENOSPC, &mapping->flags)) |
| return -ENOSPC; |
| return 0; |
| } |
| |
| /** |
| * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
| * @mapping: address space structure to write |
| * @start: offset in bytes where the range starts |
| * @end: offset in bytes where the range ends (inclusive) |
| * @sync_mode: enable synchronous operation |
| * |
| * Start writeback against all of a mapping's dirty pages that lie |
| * within the byte offsets <start, end> inclusive. |
| * |
| * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
| * opposed to a regular memory cleansing writeback. The difference between |
| * these two operations is that if a dirty page/buffer is encountered, it must |
| * be waited upon, and not just skipped over. |
| */ |
| int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| loff_t end, int sync_mode) |
| { |
| int ret; |
| struct writeback_control wbc = { |
| .sync_mode = sync_mode, |
| .nr_to_write = LONG_MAX, |
| .range_start = start, |
| .range_end = end, |
| }; |
| |
| if (!mapping_cap_writeback_dirty(mapping) || |
| !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) |
| return 0; |
| |
| wbc_attach_fdatawrite_inode(&wbc, mapping->host); |
| ret = do_writepages(mapping, &wbc); |
| wbc_detach_inode(&wbc); |
| return ret; |
| } |
| |
| static inline int __filemap_fdatawrite(struct address_space *mapping, |
| int sync_mode) |
| { |
| return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
| } |
| |
| int filemap_fdatawrite(struct address_space *mapping) |
| { |
| return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
| } |
| EXPORT_SYMBOL(filemap_fdatawrite); |
| |
| int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| loff_t end) |
| { |
| return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
| } |
| EXPORT_SYMBOL(filemap_fdatawrite_range); |
| |
| /** |
| * filemap_flush - mostly a non-blocking flush |
| * @mapping: target address_space |
| * |
| * This is a mostly non-blocking flush. Not suitable for data-integrity |
| * purposes - I/O may not be started against all dirty pages. |
| */ |
| int filemap_flush(struct address_space *mapping) |
| { |
| return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
| } |
| EXPORT_SYMBOL(filemap_flush); |
| |
| /** |
| * filemap_range_has_page - check if a page exists in range. |
| * @mapping: address space within which to check |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Find at least one page in the range supplied, usually used to check if |
| * direct writing in this range will trigger a writeback. |
| */ |
| bool filemap_range_has_page(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| pgoff_t index = start_byte >> PAGE_SHIFT; |
| pgoff_t end = end_byte >> PAGE_SHIFT; |
| struct page *page; |
| |
| if (end_byte < start_byte) |
| return false; |
| |
| if (mapping->nrpages == 0) |
| return false; |
| |
| if (!find_get_pages_range(mapping, &index, end, 1, &page)) |
| return false; |
| put_page(page); |
| return true; |
| } |
| EXPORT_SYMBOL(filemap_range_has_page); |
| |
| static void __filemap_fdatawait_range(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| pgoff_t index = start_byte >> PAGE_SHIFT; |
| pgoff_t end = end_byte >> PAGE_SHIFT; |
| struct pagevec pvec; |
| int nr_pages; |
| |
| if (end_byte < start_byte) |
| return; |
| |
| pagevec_init(&pvec, 0); |
| while (index <= end) { |
| unsigned i; |
| |
| nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, |
| end, PAGECACHE_TAG_WRITEBACK); |
| if (!nr_pages) |
| break; |
| |
| for (i = 0; i < nr_pages; i++) { |
| struct page *page = pvec.pages[i]; |
| |
| wait_on_page_writeback(page); |
| ClearPageError(page); |
| } |
| pagevec_release(&pvec); |
| cond_resched(); |
| } |
| } |
| |
| /** |
| * filemap_fdatawait_range - wait for writeback to complete |
| * @mapping: address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the given address space |
| * in the given range and wait for all of them. Check error status of |
| * the address space and return it. |
| * |
| * Since the error status of the address space is cleared by this function, |
| * callers are responsible for checking the return value and handling and/or |
| * reporting the error. |
| */ |
| int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
| loff_t end_byte) |
| { |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return filemap_check_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_range); |
| |
| /** |
| * filemap_fdatawait_range_keep_errors - wait for writeback to complete |
| * @mapping: address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the given address space in the |
| * given range and wait for all of them. Unlike filemap_fdatawait_range(), |
| * this function does not clear error status of the address space. |
| * |
| * Use this function if callers don't handle errors themselves. Expected |
| * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| * fsfreeze(8) |
| */ |
| int filemap_fdatawait_range_keep_errors(struct address_space *mapping, |
| loff_t start_byte, loff_t end_byte) |
| { |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return filemap_check_and_keep_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors); |
| |
| /** |
| * file_fdatawait_range - wait for writeback to complete |
| * @file: file pointing to address space structure to wait for |
| * @start_byte: offset in bytes where the range starts |
| * @end_byte: offset in bytes where the range ends (inclusive) |
| * |
| * Walk the list of under-writeback pages of the address space that file |
| * refers to, in the given range and wait for all of them. Check error |
| * status of the address space vs. the file->f_wb_err cursor and return it. |
| * |
| * Since the error status of the file is advanced by this function, |
| * callers are responsible for checking the return value and handling and/or |
| * reporting the error. |
| */ |
| int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte) |
| { |
| struct address_space *mapping = file->f_mapping; |
| |
| __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| return file_check_and_advance_wb_err(file); |
| } |
| EXPORT_SYMBOL(file_fdatawait_range); |
| |
| /** |
| * filemap_fdatawait_keep_errors - wait for writeback without clearing errors |
| * @mapping: address space structure to wait for |
| * |
| * Walk the list of under-writeback pages of the given address space |
| * and wait for all of them. Unlike filemap_fdatawait(), this function |
| * does not clear error status of the address space. |
| * |
| * Use this function if callers don't handle errors themselves. Expected |
| * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| * fsfreeze(8) |
| */ |
| int filemap_fdatawait_keep_errors(struct address_space *mapping) |
| { |
| __filemap_fdatawait_range(mapping, 0, LLONG_MAX); |
| return filemap_check_and_keep_errors(mapping); |
| } |
| EXPORT_SYMBOL(filemap_fdatawait_keep_errors); |
| |
| static bool mapping_needs_writeback(struct address_space *mapping) |
| { |
| return (!dax_mapping(mapping) && mapping->nrpages) || |
| (dax_mapping(mapping) && mapping->nrexceptional); |
| } |
| |
| int filemap_write_and_wait(struct address_space *mapping) |
| { |
| int err = 0; |
| |
| if (mapping_needs_writeback(mapping)) { |
| err = filemap_fdatawrite(mapping); |
| /* |
| * Even if the above returned error, the pages may be |
| * written partially (e.g. -ENOSPC), so we wait for it. |
| * But the -EIO is special case, it may indicate the worst |
| * thing (e.g. bug) happened, so we avoid waiting for it. |
| */ |
| if (err != -EIO) { |
| int err2 = filemap_fdatawait(mapping); |
| if (!err) |
| err = err2; |
| } else { |
| /* Clear any previously stored errors */ |
| filemap_check_errors(mapping); |
| } |
| } else { |
| err = filemap_check_errors(mapping); |
| } |
| return err; |
| } |
| EXPORT_SYMBOL(filemap_write_and_wait); |
| |
| /** |
| * filemap_write_and_wait_range - write out & wait on a file range |
| * @mapping: the address_space for the pages |
| * @lstart: offset in bytes where the range starts |
| * @lend: offset in bytes where the range ends (inclusive) |
| * |
| * Write out and wait upon file offsets lstart->lend, inclusive. |
| * |
| * Note that @lend is inclusive (describes the last byte to be written) so |
| * that this function can be used to write to the very end-of-file (end = -1). |
| */ |
| int filemap_write_and_wait_range(struct address_space *mapping, |
| loff_t lstart, loff_t lend) |
| { |
| int err = 0; |
| |
| if (mapping_needs_writeback(mapping)) { |
| err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| WB_SYNC_ALL); |
| /* See comment of filemap_write_and_wait() */ |
| if (err != -EIO) { |
| int err2 = filemap_fdatawait_range(mapping, |
| lstart, lend); |
| if (!err) |
| err = err2; |
| } else { |
| /* Clear any previously stored errors */ |
| filemap_check_errors(mapping); |
| } |
| } else { |
| err = filemap_check_errors(mapping); |
| } |
| return err; |
| } |
| EXPORT_SYMBOL(filemap_write_and_wait_range); |
| |
| void __filemap_set_wb_err(struct address_space *mapping, int err) |
| { |
| errseq_t eseq = errseq_set(&mapping->wb_err, err); |
| |
| trace_filemap_set_wb_err(mapping, eseq); |
| } |
| EXPORT_SYMBOL(__filemap_set_wb_err); |
| |
| /** |
| * file_check_and_advance_wb_err - report wb error (if any) that was previously |
| * and advance wb_err to current one |
| * @file: struct file on which the error is being reported |
| * |
| * When userland calls fsync (or something like nfsd does the equivalent), we |
| * want to report any writeback errors that occurred since the last fsync (or |
| * since the file was opened if there haven't been any). |
| * |
| * Grab the wb_err from the mapping. If it matches what we have in the file, |
| * then just quickly return 0. The file is all caught up. |
| * |
| * If it doesn't match, then take the mapping value, set the "seen" flag in |
| * it and try to swap it into place. If it works, or another task beat us |
| * to it with the new value, then update the f_wb_err and return the error |
| * portion. The error at this point must be reported via proper channels |
| * (a'la fsync, or NFS COMMIT operation, etc.). |
| * |
| * While we handle mapping->wb_err with atomic operations, the f_wb_err |
| * value is protected by the f_lock since we must ensure that it reflects |
| * the latest value swapped in for this file descriptor. |
| */ |
| int file_check_and_advance_wb_err(struct file *file) |
| { |
| int err = 0; |
| errseq_t old = READ_ONCE(file->f_wb_err); |
| struct address_space *mapping = file->f_mapping; |
| |
| /* Locklessly handle the common case where nothing has changed */ |
| if (errseq_check(&mapping->wb_err, old)) { |
| /* Something changed, must use slow path */ |
| spin_lock(&file->f_lock); |
| old = file->f_wb_err; |
| err = errseq_check_and_advance(&mapping->wb_err, |
| &file->f_wb_err); |
| trace_file_check_and_advance_wb_err(file, old); |
| spin_unlock(&file->f_lock); |
| } |
| |
| /* |
| * We're mostly using this function as a drop in replacement for |
| * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect |
| * that the legacy code would have had on these flags. |
| */ |
| clear_bit(AS_EIO, &mapping->flags); |
| clear_bit(AS_ENOSPC, &mapping->flags); |
| return err; |
| } |
| EXPORT_SYMBOL(file_check_and_advance_wb_err); |
| |
| /** |
| * file_write_and_wait_range - write out & wait on a file range |
| * @file: file pointing to address_space with pages |
| * @lstart: offset in bytes where the range starts |
| * @lend: offset in bytes where the range ends (inclusive) |
| * |
| * Write out and wait upon file offsets lstart->lend, inclusive. |
| * |
| * Note that @lend is inclusive (describes the last byte to be written) so |
| * that this function can be used to write to the very end-of-file (end = -1). |
| * |
| * After writing out and waiting on the data, we check and advance the |
| * f_wb_err cursor to the latest value, and return any errors detected there. |
| */ |
| int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend) |
| { |
| int err = 0, err2; |
| struct address_space *mapping = file->f_mapping; |
| |
| if (mapping_needs_writeback(mapping)) { |
| err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| WB_SYNC_ALL); |
| /* See comment of filemap_write_and_wait() */ |
| if (err != -EIO) |
| __filemap_fdatawait_range(mapping, lstart, lend); |
| } |
| err2 = file_check_and_advance_wb_err(file); |
| if (!err) |
| err = err2; |
| return err; |
| } |
| EXPORT_SYMBOL(file_write_and_wait_range); |
| |
| /** |
| * replace_page_cache_page - replace a pagecache page with a new one |
| * @old: page to be replaced |
| * @new: page to replace with |
| * @gfp_mask: allocation mode |
| * |
| * This function replaces a page in the pagecache with a new one. On |
| * success it acquires the pagecache reference for the new page and |
| * drops it for the old page. Both the old and new pages must be |
| * locked. This function does not add the new page to the LRU, the |
| * caller must do that. |
| * |
| * The remove + add is atomic. The only way this function can fail is |
| * memory allocation failure. |
| */ |
| int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) |
| { |
| int error; |
| |
| VM_BUG_ON_PAGE(!PageLocked(old), old); |
| VM_BUG_ON_PAGE(!PageLocked(new), new); |
| VM_BUG_ON_PAGE(new->mapping, new); |
| |
| error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK); |
| if (!error) { |
| struct address_space *mapping = old->mapping; |
| void (*freepage)(struct page *); |
| unsigned long flags; |
| |
| pgoff_t offset = old->index; |
| freepage = mapping->a_ops->freepage; |
| |
| get_page(new); |
| new->mapping = mapping; |
| new->index = offset; |
| |
| spin_lock_irqsave(&mapping->tree_lock, flags); |
| __delete_from_page_cache(old, NULL); |
| error = page_cache_tree_insert(mapping, new, NULL); |
| BUG_ON(error); |
| |
| /* |
| * hugetlb pages do not participate in page cache accounting. |
| */ |
| if (!PageHuge(new)) |
| __inc_node_page_state(new, NR_FILE_PAGES); |
| if (PageSwapBacked(new)) |
| __inc_node_page_state(new, NR_SHMEM); |
| spin_unlock_irqrestore(&mapping->tree_lock, flags); |
| mem_cgroup_migrate(old, new); |
| radix_tree_preload_end(); |
| if (freepage) |
| freepage(old); |
| put_page(old); |
| } |
| |
| return error; |
| } |
| EXPORT_SYMBOL_GPL(replace_page_cache_page); |
| |
| static int __add_to_page_cache_locked(struct page *page, |
| struct address_space *mapping, |
| pgoff_t offset, gfp_t gfp_mask, |
| void **shadowp) |
| { |
| int huge = PageHuge(page); |
| struct mem_cgroup *memcg; |
| int error; |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(PageSwapBacked(page), page); |
| |
| if (!huge) { |
| error = mem_cgroup_try_charge(page, current->mm, |
| gfp_mask, &memcg, false); |
| if (error) |
| return error; |
| } |
| |
| error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK); |
| if (error) { |
| if (!huge) |
| mem_cgroup_cancel_charge(page, memcg, false); |
| return error; |
| } |
| |
| get_page(page); |
| page->mapping = mapping; |
| page->index = offset; |
| |
| spin_lock_irq(&mapping->tree_lock); |
| error = page_cache_tree_insert(mapping, page, shadowp); |
| radix_tree_preload_end(); |
| if (unlikely(error)) |
| goto err_insert; |
| |
| /* hugetlb pages do not participate in page cache accounting. */ |
| if (!huge) |
| __inc_node_page_state(page, NR_FILE_PAGES); |
| spin_unlock_irq(&mapping->tree_lock); |
| if (!huge) |
| mem_cgroup_commit_charge(page, memcg, false, false); |
| trace_mm_filemap_add_to_page_cache(page); |
| return 0; |
| err_insert: |
| page->mapping = NULL; |
| /* Leave page->index set: truncation relies upon it */ |
| spin_unlock_irq(&mapping->tree_lock); |
| if (!huge) |
| mem_cgroup_cancel_charge(page, memcg, false); |
| put_page(page); |
| return error; |
| } |
| |
| /** |
| * add_to_page_cache_locked - add a locked page to the pagecache |
| * @page: page to add |
| * @mapping: the page's address_space |
| * @offset: page index |
| * @gfp_mask: page allocation mode |
| * |
| * This function is used to add a page to the pagecache. It must be locked. |
| * This function does not add the page to the LRU. The caller must do that. |
| */ |
| int add_to_page_cache_locked(struct page *page, struct address_space *mapping, |
| pgoff_t offset, gfp_t gfp_mask) |
| { |
| return __add_to_page_cache_locked(page, mapping, offset, |
| gfp_mask, NULL); |
| } |
| EXPORT_SYMBOL(add_to_page_cache_locked); |
| |
| int add_to_page_cache_lru(struct page *page, struct address_space *mapping, |
| pgoff_t offset, gfp_t gfp_mask) |
| { |
| void *shadow = NULL; |
| int ret; |
| |
| __SetPageLocked(page); |
| ret = __add_to_page_cache_locked(page, mapping, offset, |
| gfp_mask, &shadow); |
| if (unlikely(ret)) |
| __ClearPageLocked(page); |
| else { |
| /* |
| * The page might have been evicted from cache only |
| * recently, in which case it should be activated like |
| * any other repeatedly accessed page. |
| * The exception is pages getting rewritten; evicting other |
| * data from the working set, only to cache data that will |
| * get overwritten with something else, is a waste of memory. |
| */ |
| WARN_ON_ONCE(PageActive(page)); |
| if (!(gfp_mask & __GFP_WRITE) && shadow) |
| workingset_refault(page, shadow); |
| lru_cache_add(page); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(add_to_page_cache_lru); |
| |
| #ifdef CONFIG_NUMA |
| struct page *__page_cache_alloc(gfp_t gfp) |
| { |
| int n; |
| struct page *page; |
| |
| if (cpuset_do_page_mem_spread()) { |
| unsigned int cpuset_mems_cookie; |
| do { |
| cpuset_mems_cookie = read_mems_allowed_begin(); |
| n = cpuset_mem_spread_node(); |
| page = __alloc_pages_node(n, gfp, 0); |
| } while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); |
| |
| return page; |
| } |
| return alloc_pages(gfp, 0); |
| } |
| EXPORT_SYMBOL(__page_cache_alloc); |
| #endif |
| |
| /* |
| * In order to wait for pages to become available there must be |
| * waitqueues associated with pages. By using a hash table of |
| * waitqueues where the bucket discipline is to maintain all |
| * waiters on the same queue and wake all when any of the pages |
| * become available, and for the woken contexts to check to be |
| * sure the appropriate page became available, this saves space |
| * at a cost of "thundering herd" phenomena during rare hash |
| * collisions. |
| */ |
| #define PAGE_WAIT_TABLE_BITS 8 |
| #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) |
| static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; |
| |
| static wait_queue_head_t *page_waitqueue(struct page *page) |
| { |
| return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)]; |
| } |
| |
| void __init pagecache_init(void) |
| { |
| int i; |
| |
| for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) |
| init_waitqueue_head(&page_wait_table[i]); |
| |
| page_writeback_init(); |
| } |
| |
| /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */ |
| struct wait_page_key { |
| struct page *page; |
| int bit_nr; |
| int page_match; |
| }; |
| |
| struct wait_page_queue { |
| struct page *page; |
| int bit_nr; |
| wait_queue_entry_t wait; |
| }; |
| |
| static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) |
| { |
| struct wait_page_key *key = arg; |
| struct wait_page_queue *wait_page |
| = container_of(wait, struct wait_page_queue, wait); |
| |
| if (wait_page->page != key->page) |
| return 0; |
| key->page_match = 1; |
| |
| if (wait_page->bit_nr != key->bit_nr) |
| return 0; |
| |
| /* Stop walking if it's locked */ |
| if (test_bit(key->bit_nr, &key->page->flags)) |
| return -1; |
| |
| return autoremove_wake_function(wait, mode, sync, key); |
| } |
| |
| static void wake_up_page_bit(struct page *page, int bit_nr) |
| { |
| wait_queue_head_t *q = page_waitqueue(page); |
| struct wait_page_key key; |
| unsigned long flags; |
| wait_queue_entry_t bookmark; |
| |
| key.page = page; |
| key.bit_nr = bit_nr; |
| key.page_match = 0; |
| |
| bookmark.flags = 0; |
| bookmark.private = NULL; |
| bookmark.func = NULL; |
| INIT_LIST_HEAD(&bookmark.entry); |
| |
| spin_lock_irqsave(&q->lock, flags); |
| __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| |
| while (bookmark.flags & WQ_FLAG_BOOKMARK) { |
| /* |
| * Take a breather from holding the lock, |
| * allow pages that finish wake up asynchronously |
| * to acquire the lock and remove themselves |
| * from wait queue |
| */ |
| spin_unlock_irqrestore(&q->lock, flags); |
| cpu_relax(); |
| spin_lock_irqsave(&q->lock, flags); |
| __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| } |
| |
| /* |
| * It is possible for other pages to have collided on the waitqueue |
| * hash, so in that case check for a page match. That prevents a long- |
| * term waiter |
| * |
| * It is still possible to miss a case here, when we woke page waiters |
| * and removed them from the waitqueue, but there are still other |
| * page waiters. |
| */ |
| if (!waitqueue_active(q) || !key.page_match) { |
| ClearPageWaiters(page); |
| /* |
| * It's possible to miss clearing Waiters here, when we woke |
| * our page waiters, but the hashed waitqueue has waiters for |
| * other pages on it. |
| * |
| * That's okay, it's a rare case. The next waker will clear it. |
| */ |
| } |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| |
| static void wake_up_page(struct page *page, int bit) |
| { |
| if (!PageWaiters(page)) |
| return; |
| wake_up_page_bit(page, bit); |
| } |
| |
| static inline int wait_on_page_bit_common(wait_queue_head_t *q, |
| struct page *page, int bit_nr, int state, bool lock) |
| { |
| struct wait_page_queue wait_page; |
| wait_queue_entry_t *wait = &wait_page.wait; |
| bool thrashing = false; |
| unsigned long pflags; |
| int ret = 0; |
| |
| if (bit_nr == PG_locked && |
| !PageUptodate(page) && PageWorkingset(page)) { |
| if (!PageSwapBacked(page)) |
| delayacct_thrashing_start(); |
| psi_memstall_enter(&pflags); |
| thrashing = true; |
| } |
| |
| init_wait(wait); |
| wait->flags = lock ? WQ_FLAG_EXCLUSIVE : 0; |
| wait->func = wake_page_function; |
| wait_page.page = page; |
| wait_page.bit_nr = bit_nr; |
| |
| for (;;) { |
| spin_lock_irq(&q->lock); |
| |
| if (likely(list_empty(&wait->entry))) { |
| __add_wait_queue_entry_tail(q, wait); |
| SetPageWaiters(page); |
| } |
| |
| set_current_state(state); |
| |
| spin_unlock_irq(&q->lock); |
| |
| if (likely(test_bit(bit_nr, &page->flags))) { |
| io_schedule(); |
| } |
| |
| if (lock) { |
| if (!test_and_set_bit_lock(bit_nr, &page->flags)) |
| break; |
| } else { |
| if (!test_bit(bit_nr, &page->flags)) |
| break; |
| } |
| |
| if (unlikely(signal_pending_state(state, current))) { |
| ret = -EINTR; |
| break; |
| } |
| } |
| |
| finish_wait(q, wait); |
| |
| if (thrashing) { |
| if (!PageSwapBacked(page)) |
| delayacct_thrashing_end(); |
| psi_memstall_leave(&pflags); |
| } |
| |
| /* |
| * A signal could leave PageWaiters set. Clearing it here if |
| * !waitqueue_active would be possible (by open-coding finish_wait), |
| * but still fail to catch it in the case of wait hash collision. We |
| * already can fail to clear wait hash collision cases, so don't |
| * bother with signals either. |
| */ |
| |
| return ret; |
| } |
| |
| void wait_on_page_bit(struct page *page, int bit_nr) |
| { |
| wait_queue_head_t *q = page_waitqueue(page); |
| wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false); |
| } |
| EXPORT_SYMBOL(wait_on_page_bit); |
| |
| int wait_on_page_bit_killable(struct page *page, int bit_nr) |
| { |
| wait_queue_head_t *q = page_waitqueue(page); |
| return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false); |
| } |
| |
| /** |
| * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue |
| * @page: Page defining the wait queue of interest |
| * @waiter: Waiter to add to the queue |
| * |
| * Add an arbitrary @waiter to the wait queue for the nominated @page. |
| */ |
| void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter) |
| { |
| wait_queue_head_t *q = page_waitqueue(page); |
| unsigned long flags; |
| |
| spin_lock_irqsave(&q->lock, flags); |
| __add_wait_queue_entry_tail(q, waiter); |
| SetPageWaiters(page); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL_GPL(add_page_wait_queue); |
| |
| #ifndef clear_bit_unlock_is_negative_byte |
| |
| /* |
| * PG_waiters is the high bit in the same byte as PG_lock. |
| * |
| * On x86 (and on many other architectures), we can clear PG_lock and |
| * test the sign bit at the same time. But if the architecture does |
| * not support that special operation, we just do this all by hand |
| * instead. |
| * |
| * The read of PG_waiters has to be after (or concurrently with) PG_locked |
| * being cleared, but a memory barrier should be unneccssary since it is |
| * in the same byte as PG_locked. |
| */ |
| static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) |
| { |
| clear_bit_unlock(nr, mem); |
| /* smp_mb__after_atomic(); */ |
| return test_bit(PG_waiters, mem); |
| } |
| |
| #endif |
| |
| /** |
| * unlock_page - unlock a locked page |
| * @page: the page |
| * |
| * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). |
| * Also wakes sleepers in wait_on_page_writeback() because the wakeup |
| * mechanism between PageLocked pages and PageWriteback pages is shared. |
| * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. |
| * |
| * Note that this depends on PG_waiters being the sign bit in the byte |
| * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to |
| * clear the PG_locked bit and test PG_waiters at the same time fairly |
| * portably (architectures that do LL/SC can test any bit, while x86 can |
| * test the sign bit). |
| */ |
| void unlock_page(struct page *page) |
| { |
| BUILD_BUG_ON(PG_waiters != 7); |
| page = compound_head(page); |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) |
| wake_up_page_bit(page, PG_locked); |
| } |
| EXPORT_SYMBOL(unlock_page); |
| |
| /** |
| * end_page_writeback - end writeback against a page |
| * @page: the page |
| */ |
| void end_page_writeback(struct page *page) |
| { |
| /* |
| * TestClearPageReclaim could be used here but it is an atomic |
| * operation and overkill in this particular case. Failing to |
| * shuffle a page marked for immediate reclaim is too mild to |
| * justify taking an atomic operation penalty at the end of |
| * ever page writeback. |
| */ |
| if (PageReclaim(page)) { |
| ClearPageReclaim(page); |
| rotate_reclaimable_page(page); |
| } |
| |
| if (!test_clear_page_writeback(page)) |
| BUG(); |
| |
| smp_mb__after_atomic(); |
| wake_up_page(page, PG_writeback); |
| } |
| EXPORT_SYMBOL(end_page_writeback); |
| |
| /* |
| * After completing I/O on a page, call this routine to update the page |
| * flags appropriately |
| */ |
| void page_endio(struct page *page, bool is_write, int err) |
| { |
| if (!is_write) { |
| if (!err) { |
| SetPageUptodate(page); |
| } else { |
| ClearPageUptodate(page); |
| SetPageError(page); |
| } |
| unlock_page(page); |
| } else { |
| if (err) { |
| struct address_space *mapping; |
| |
| SetPageError(page); |
| mapping = page_mapping(page); |
| if (mapping) |
| mapping_set_error(mapping, err); |
| } |
| end_page_writeback(page); |
| } |
| } |
| EXPORT_SYMBOL_GPL(page_endio); |
| |
| /** |
| * __lock_page - get a lock on the page, assuming we need to sleep to get it |
| * @__page: the page to lock |
| */ |
| void __lock_page(struct page *__page) |
| { |
| struct page *page = compound_head(__page); |
| wait_queue_head_t *q = page_waitqueue(page); |
| wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true); |
| } |
| EXPORT_SYMBOL(__lock_page); |
| |
| int __lock_page_killable(struct page *__page) |
| { |
| struct page *page = compound_head(__page); |
| wait_queue_head_t *q = page_waitqueue(page); |
| return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true); |
| } |
| EXPORT_SYMBOL_GPL(__lock_page_killable); |
| |
| /* |
| * Return values: |
| * 1 - page is locked; mmap_sem is still held. |
| * 0 - page is not locked. |
| * mmap_sem has been released (up_read()), unless flags had both |
| * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in |
| * which case mmap_sem is still held. |
| * |
| * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1 |
| * with the page locked and the mmap_sem unperturbed. |
| */ |
| int __lock_page_or_retry(struct page *page, struct mm_struct *mm, |
| unsigned int flags) |
| { |
| if (flags & FAULT_FLAG_ALLOW_RETRY) { |
| /* |
| * CAUTION! In this case, mmap_sem is not released |
| * even though return 0. |
| */ |
| if (flags & FAULT_FLAG_RETRY_NOWAIT) |
| return 0; |
| |
| up_read(&mm->mmap_sem); |
| if (flags & FAULT_FLAG_KILLABLE) |
| wait_on_page_locked_killable(page); |
| else |
| wait_on_page_locked(page); |
| return 0; |
| } else { |
| if (flags & FAULT_FLAG_KILLABLE) { |
| int ret; |
| |
| ret = __lock_page_killable(page); |
| if (ret) { |
| up_read(&mm->mmap_sem); |
| return 0; |
| } |
| } else |
| __lock_page(page); |
| return 1; |
| } |
| } |
| |
| /** |
| * page_cache_next_hole - find the next hole (not-present entry) |
| * @mapping: mapping |
| * @index: index |
| * @max_scan: maximum range to search |
| * |
| * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the |
| * lowest indexed hole. |
| * |
| * Returns: the index of the hole if found, otherwise returns an index |
| * outside of the set specified (in which case 'return - index >= |
| * max_scan' will be true). In rare cases of index wrap-around, 0 will |
| * be returned. |
| * |
| * page_cache_next_hole may be called under rcu_read_lock. However, |
| * like radix_tree_gang_lookup, this will not atomically search a |
| * snapshot of the tree at a single point in time. For example, if a |
| * hole is created at index 5, then subsequently a hole is created at |
| * index 10, page_cache_next_hole covering both indexes may return 10 |
| * if called under rcu_read_lock. |
| */ |
| pgoff_t page_cache_next_hole(struct address_space *mapping, |
| pgoff_t index, unsigned long max_scan) |
| { |
| unsigned long i; |
| |
| for (i = 0; i < max_scan; i++) { |
| struct page *page; |
| |
| page = radix_tree_lookup(&mapping->page_tree, index); |
| if (!page || radix_tree_exceptional_entry(page)) |
| break; |
| index++; |
| if (index == 0) |
| break; |
| } |
| |
| return index; |
| } |
| EXPORT_SYMBOL(page_cache_next_hole); |
| |
| /** |
| * page_cache_prev_hole - find the prev hole (not-present entry) |
| * @mapping: mapping |
| * @index: index |
| * @max_scan: maximum range to search |
| * |
| * Search backwards in the range [max(index-max_scan+1, 0), index] for |
| * the first hole. |
| * |
| * Returns: the index of the hole if found, otherwise returns an index |
| * outside of the set specified (in which case 'index - return >= |
| * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX |
| * will be returned. |
| * |
| * page_cache_prev_hole may be called under rcu_read_lock. However, |
| * like radix_tree_gang_lookup, this will not atomically search a |
| * snapshot of the tree at a single point in time. For example, if a |
| * hole is created at index 10, then subsequently a hole is created at |
| * index 5, page_cache_prev_hole covering both indexes may return 5 if |
| * called under rcu_read_lock. |
| */ |
| pgoff_t page_cache_prev_hole(struct address_space *mapping, |
| pgoff_t index, unsigned long max_scan) |
| { |
| unsigned long i; |
| |
| for (i = 0; i < max_scan; i++) { |
| struct page *page; |
| |
| page = radix_tree_lookup(&mapping->page_tree, index); |
| if (!page || radix_tree_exceptional_entry(page)) |
| break; |
| index--; |
| if (index == ULONG_MAX) |
| break; |
| } |
| |
| return index; |
| } |
| EXPORT_SYMBOL(page_cache_prev_hole); |
| |
| /** |
| * find_get_entry - find and get a page cache entry |
| * @mapping: the address_space to search |
| * @offset: the page cache index |
| * |
| * Looks up the page cache slot at @mapping & @offset. If there is a |
| * page cache page, it is returned with an increased refcount. |
| * |
| * If the slot holds a shadow entry of a previously evicted page, or a |
| * swap entry from shmem/tmpfs, it is returned. |
| * |
| * Otherwise, %NULL is returned. |
| */ |
| struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) |
| { |
| void **pagep; |
| struct page *head, *page; |
| |
| rcu_read_lock(); |
| repeat: |
| page = NULL; |
| pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); |
| if (pagep) { |
| page = radix_tree_deref_slot(pagep); |
| if (unlikely(!page)) |
| goto out; |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) |
| goto repeat; |
| /* |
| * A shadow entry of a recently evicted page, |
| * or a swap entry from shmem/tmpfs. Return |
| * it without attempting to raise page count. |
| */ |
| goto out; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* |
| * Has the page moved? |
| * This is part of the lockless pagecache protocol. See |
| * include/linux/pagemap.h for details. |
| */ |
| if (unlikely(page != *pagep)) { |
| put_page(head); |
| goto repeat; |
| } |
| } |
| out: |
| rcu_read_unlock(); |
| |
| return page; |
| } |
| EXPORT_SYMBOL(find_get_entry); |
| |
| /** |
| * find_lock_entry - locate, pin and lock a page cache entry |
| * @mapping: the address_space to search |
| * @offset: the page cache index |
| * |
| * Looks up the page cache slot at @mapping & @offset. If there is a |
| * page cache page, it is returned locked and with an increased |
| * refcount. |
| * |
| * If the slot holds a shadow entry of a previously evicted page, or a |
| * swap entry from shmem/tmpfs, it is returned. |
| * |
| * Otherwise, %NULL is returned. |
| * |
| * find_lock_entry() may sleep. |
| */ |
| struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset) |
| { |
| struct page *page; |
| |
| repeat: |
| page = find_get_entry(mapping, offset); |
| if (page && !radix_tree_exception(page)) { |
| lock_page(page); |
| /* Has the page been truncated? */ |
| if (unlikely(page_mapping(page) != mapping)) { |
| unlock_page(page); |
| put_page(page); |
| goto repeat; |
| } |
| VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); |
| } |
| return page; |
| } |
| EXPORT_SYMBOL(find_lock_entry); |
| |
| /** |
| * pagecache_get_page - find and get a page reference |
| * @mapping: the address_space to search |
| * @offset: the page index |
| * @fgp_flags: PCG flags |
| * @gfp_mask: gfp mask to use for the page cache data page allocation |
| * |
| * Looks up the page cache slot at @mapping & @offset. |
| * |
| * PCG flags modify how the page is returned. |
| * |
| * @fgp_flags can be: |
| * |
| * - FGP_ACCESSED: the page will be marked accessed |
| * - FGP_LOCK: Page is return locked |
| * - FGP_CREAT: If page is not present then a new page is allocated using |
| * @gfp_mask and added to the page cache and the VM's LRU |
| * list. The page is returned locked and with an increased |
| * refcount. |
| * - FGP_FOR_MMAP: Similar to FGP_CREAT, only we want to allow the caller to do |
| * its own locking dance if the page is already in cache, or unlock the page |
| * before returning if we had to add the page to pagecache. |
| * |
| * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even |
| * if the GFP flags specified for FGP_CREAT are atomic. |
| * |
| * If there is a page cache page, it is returned with an increased refcount. |
| */ |
| struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, |
| int fgp_flags, gfp_t gfp_mask) |
| { |
| struct page *page; |
| |
| repeat: |
| page = find_get_entry(mapping, offset); |
| if (radix_tree_exceptional_entry(page)) |
| page = NULL; |
| if (!page) |
| goto no_page; |
| |
| if (fgp_flags & FGP_LOCK) { |
| if (fgp_flags & FGP_NOWAIT) { |
| if (!trylock_page(page)) { |
| put_page(page); |
| return NULL; |
| } |
| } else { |
| lock_page(page); |
| } |
| |
| /* Has the page been truncated? */ |
| if (unlikely(page->mapping != mapping)) { |
| unlock_page(page); |
| put_page(page); |
| goto repeat; |
| } |
| VM_BUG_ON_PAGE(page->index != offset, page); |
| } |
| |
| if (page && (fgp_flags & FGP_ACCESSED)) |
| mark_page_accessed(page); |
| |
| no_page: |
| if (!page && (fgp_flags & FGP_CREAT)) { |
| int err; |
| if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping)) |
| gfp_mask |= __GFP_WRITE; |
| if (fgp_flags & FGP_NOFS) |
| gfp_mask &= ~__GFP_FS; |
| |
| page = __page_cache_alloc(gfp_mask); |
| if (!page) |
| return NULL; |
| |
| if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) |
| fgp_flags |= FGP_LOCK; |
| |
| /* Init accessed so avoid atomic mark_page_accessed later */ |
| if (fgp_flags & FGP_ACCESSED) |
| __SetPageReferenced(page); |
| |
| err = add_to_page_cache_lru(page, mapping, offset, gfp_mask); |
| if (unlikely(err)) { |
| put_page(page); |
| page = NULL; |
| if (err == -EEXIST) |
| goto repeat; |
| } |
| |
| /* |
| * add_to_page_cache_lru locks the page, and for mmap we expect |
| * an unlocked page. |
| */ |
| if (page && (fgp_flags & FGP_FOR_MMAP)) |
| unlock_page(page); |
| } |
| |
| return page; |
| } |
| EXPORT_SYMBOL(pagecache_get_page); |
| |
| /** |
| * find_get_entries - gang pagecache lookup |
| * @mapping: The address_space to search |
| * @start: The starting page cache index |
| * @nr_entries: The maximum number of entries |
| * @entries: Where the resulting entries are placed |
| * @indices: The cache indices corresponding to the entries in @entries |
| * |
| * find_get_entries() will search for and return a group of up to |
| * @nr_entries entries in the mapping. The entries are placed at |
| * @entries. find_get_entries() takes a reference against any actual |
| * pages it returns. |
| * |
| * The search returns a group of mapping-contiguous page cache entries |
| * with ascending indexes. There may be holes in the indices due to |
| * not-present pages. |
| * |
| * Any shadow entries of evicted pages, or swap entries from |
| * shmem/tmpfs, are included in the returned array. |
| * |
| * find_get_entries() returns the number of pages and shadow entries |
| * which were found. |
| */ |
| unsigned find_get_entries(struct address_space *mapping, |
| pgoff_t start, unsigned int nr_entries, |
| struct page **entries, pgoff_t *indices) |
| { |
| void **slot; |
| unsigned int ret = 0; |
| struct radix_tree_iter iter; |
| |
| if (!nr_entries) |
| return 0; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { |
| struct page *head, *page; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| if (unlikely(!page)) |
| continue; |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| /* |
| * A shadow entry of a recently evicted page, a swap |
| * entry from shmem/tmpfs or a DAX entry. Return it |
| * without attempting to raise page count. |
| */ |
| goto export; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| export: |
| indices[ret] = iter.index; |
| entries[ret] = page; |
| if (++ret == nr_entries) |
| break; |
| } |
| rcu_read_unlock(); |
| return ret; |
| } |
| |
| /** |
| * find_get_pages_range - gang pagecache lookup |
| * @mapping: The address_space to search |
| * @start: The starting page index |
| * @end: The final page index (inclusive) |
| * @nr_pages: The maximum number of pages |
| * @pages: Where the resulting pages are placed |
| * |
| * find_get_pages_range() will search for and return a group of up to @nr_pages |
| * pages in the mapping starting at index @start and up to index @end |
| * (inclusive). The pages are placed at @pages. find_get_pages_range() takes |
| * a reference against the returned pages. |
| * |
| * The search returns a group of mapping-contiguous pages with ascending |
| * indexes. There may be holes in the indices due to not-present pages. |
| * We also update @start to index the next page for the traversal. |
| * |
| * find_get_pages_range() returns the number of pages which were found. If this |
| * number is smaller than @nr_pages, the end of specified range has been |
| * reached. |
| */ |
| unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, |
| pgoff_t end, unsigned int nr_pages, |
| struct page **pages) |
| { |
| struct radix_tree_iter iter; |
| void **slot; |
| unsigned ret = 0; |
| |
| if (unlikely(!nr_pages)) |
| return 0; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, *start) { |
| struct page *head, *page; |
| |
| if (iter.index > end) |
| break; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| if (unlikely(!page)) |
| continue; |
| |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| /* |
| * A shadow entry of a recently evicted page, |
| * or a swap entry from shmem/tmpfs. Skip |
| * over it. |
| */ |
| continue; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| pages[ret] = page; |
| if (++ret == nr_pages) { |
| *start = pages[ret - 1]->index + 1; |
| goto out; |
| } |
| } |
| |
| /* |
| * We come here when there is no page beyond @end. We take care to not |
| * overflow the index @start as it confuses some of the callers. This |
| * breaks the iteration when there is page at index -1 but that is |
| * already broken anyway. |
| */ |
| if (end == (pgoff_t)-1) |
| *start = (pgoff_t)-1; |
| else |
| *start = end + 1; |
| out: |
| rcu_read_unlock(); |
| |
| return ret; |
| } |
| |
| /** |
| * find_get_pages_contig - gang contiguous pagecache lookup |
| * @mapping: The address_space to search |
| * @index: The starting page index |
| * @nr_pages: The maximum number of pages |
| * @pages: Where the resulting pages are placed |
| * |
| * find_get_pages_contig() works exactly like find_get_pages(), except |
| * that the returned number of pages are guaranteed to be contiguous. |
| * |
| * find_get_pages_contig() returns the number of pages which were found. |
| */ |
| unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, |
| unsigned int nr_pages, struct page **pages) |
| { |
| struct radix_tree_iter iter; |
| void **slot; |
| unsigned int ret = 0; |
| |
| if (unlikely(!nr_pages)) |
| return 0; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) { |
| struct page *head, *page; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| /* The hole, there no reason to continue */ |
| if (unlikely(!page)) |
| break; |
| |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| /* |
| * A shadow entry of a recently evicted page, |
| * or a swap entry from shmem/tmpfs. Stop |
| * looking for contiguous pages. |
| */ |
| break; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* |
| * must check mapping and index after taking the ref. |
| * otherwise we can get both false positives and false |
| * negatives, which is just confusing to the caller. |
| */ |
| if (page->mapping == NULL || page_to_pgoff(page) != iter.index) { |
| put_page(page); |
| break; |
| } |
| |
| pages[ret] = page; |
| if (++ret == nr_pages) |
| break; |
| } |
| rcu_read_unlock(); |
| return ret; |
| } |
| EXPORT_SYMBOL(find_get_pages_contig); |
| |
| /** |
| * find_get_pages_range_tag - find and return pages in given range matching @tag |
| * @mapping: the address_space to search |
| * @index: the starting page index |
| * @end: The final page index (inclusive) |
| * @tag: the tag index |
| * @nr_pages: the maximum number of pages |
| * @pages: where the resulting pages are placed |
| * |
| * Like find_get_pages, except we only return pages which are tagged with |
| * @tag. We update @index to index the next page for the traversal. |
| */ |
| unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, |
| pgoff_t end, int tag, unsigned int nr_pages, |
| struct page **pages) |
| { |
| struct radix_tree_iter iter; |
| void **slot; |
| unsigned ret = 0; |
| |
| if (unlikely(!nr_pages)) |
| return 0; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_tagged(slot, &mapping->page_tree, |
| &iter, *index, tag) { |
| struct page *head, *page; |
| |
| if (iter.index > end) |
| break; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| if (unlikely(!page)) |
| continue; |
| |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| /* |
| * A shadow entry of a recently evicted page. |
| * |
| * Those entries should never be tagged, but |
| * this tree walk is lockless and the tags are |
| * looked up in bulk, one radix tree node at a |
| * time, so there is a sizable window for page |
| * reclaim to evict a page we saw tagged. |
| * |
| * Skip over it. |
| */ |
| continue; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| pages[ret] = page; |
| if (++ret == nr_pages) { |
| *index = pages[ret - 1]->index + 1; |
| goto out; |
| } |
| } |
| |
| /* |
| * We come here when we got at @end. We take care to not overflow the |
| * index @index as it confuses some of the callers. This breaks the |
| * iteration when there is page at index -1 but that is already broken |
| * anyway. |
| */ |
| if (end == (pgoff_t)-1) |
| *index = (pgoff_t)-1; |
| else |
| *index = end + 1; |
| out: |
| rcu_read_unlock(); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(find_get_pages_range_tag); |
| |
| /** |
| * find_get_entries_tag - find and return entries that match @tag |
| * @mapping: the address_space to search |
| * @start: the starting page cache index |
| * @tag: the tag index |
| * @nr_entries: the maximum number of entries |
| * @entries: where the resulting entries are placed |
| * @indices: the cache indices corresponding to the entries in @entries |
| * |
| * Like find_get_entries, except we only return entries which are tagged with |
| * @tag. |
| */ |
| unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, |
| int tag, unsigned int nr_entries, |
| struct page **entries, pgoff_t *indices) |
| { |
| void **slot; |
| unsigned int ret = 0; |
| struct radix_tree_iter iter; |
| |
| if (!nr_entries) |
| return 0; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_tagged(slot, &mapping->page_tree, |
| &iter, start, tag) { |
| struct page *head, *page; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| if (unlikely(!page)) |
| continue; |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| |
| /* |
| * A shadow entry of a recently evicted page, a swap |
| * entry from shmem/tmpfs or a DAX entry. Return it |
| * without attempting to raise page count. |
| */ |
| goto export; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| export: |
| indices[ret] = iter.index; |
| entries[ret] = page; |
| if (++ret == nr_entries) |
| break; |
| } |
| rcu_read_unlock(); |
| return ret; |
| } |
| EXPORT_SYMBOL(find_get_entries_tag); |
| |
| /* |
| * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
| * a _large_ part of the i/o request. Imagine the worst scenario: |
| * |
| * ---R__________________________________________B__________ |
| * ^ reading here ^ bad block(assume 4k) |
| * |
| * read(R) => miss => readahead(R...B) => media error => frustrating retries |
| * => failing the whole request => read(R) => read(R+1) => |
| * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
| * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
| * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
| * |
| * It is going insane. Fix it by quickly scaling down the readahead size. |
| */ |
| static void shrink_readahead_size_eio(struct file *filp, |
| struct file_ra_state *ra) |
| { |
| ra->ra_pages /= 4; |
| } |
| |
| /** |
| * generic_file_buffered_read - generic file read routine |
| * @iocb: the iocb to read |
| * @iter: data destination |
| * @written: already copied |
| * |
| * This is a generic file read routine, and uses the |
| * mapping->a_ops->readpage() function for the actual low-level stuff. |
| * |
| * This is really ugly. But the goto's actually try to clarify some |
| * of the logic when it comes to error handling etc. |
| */ |
| static ssize_t generic_file_buffered_read(struct kiocb *iocb, |
| struct iov_iter *iter, ssize_t written) |
| { |
| struct file *filp = iocb->ki_filp; |
| struct address_space *mapping = filp->f_mapping; |
| struct inode *inode = mapping->host; |
| struct file_ra_state *ra = &filp->f_ra; |
| loff_t *ppos = &iocb->ki_pos; |
| pgoff_t index; |
| pgoff_t last_index; |
| pgoff_t prev_index; |
| unsigned long offset; /* offset into pagecache page */ |
| unsigned int prev_offset; |
| int error = 0; |
| |
| if (unlikely(*ppos >= inode->i_sb->s_maxbytes)) |
| return 0; |
| iov_iter_truncate(iter, inode->i_sb->s_maxbytes); |
| |
| index = *ppos >> PAGE_SHIFT; |
| prev_index = ra->prev_pos >> PAGE_SHIFT; |
| prev_offset = ra->prev_pos & (PAGE_SIZE-1); |
| last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; |
| offset = *ppos & ~PAGE_MASK; |
| |
| for (;;) { |
| struct page *page; |
| pgoff_t end_index; |
| loff_t isize; |
| unsigned long nr, ret; |
| |
| cond_resched(); |
| find_page: |
| if (fatal_signal_pending(current)) { |
| error = -EINTR; |
| goto out; |
| } |
| |
| page = find_get_page(mapping, index); |
| if (!page) { |
| if (iocb->ki_flags & IOCB_NOWAIT) |
| goto would_block; |
| page_cache_sync_readahead(mapping, |
| ra, filp, |
| index, last_index - index); |
| page = find_get_page(mapping, index); |
| if (unlikely(page == NULL)) |
| goto no_cached_page; |
| } |
| if (PageReadahead(page)) { |
| page_cache_async_readahead(mapping, |
| ra, filp, page, |
| index, last_index - index); |
| } |
| if (!PageUptodate(page)) { |
| if (iocb->ki_flags & IOCB_NOWAIT) { |
| put_page(page); |
| goto would_block; |
| } |
| |
| /* |
| * See comment in do_read_cache_page on why |
| * wait_on_page_locked is used to avoid unnecessarily |
| * serialisations and why it's safe. |
| */ |
| error = wait_on_page_locked_killable(page); |
| if (unlikely(error)) |
| goto readpage_error; |
| if (PageUptodate(page)) |
| goto page_ok; |
| |
| if (inode->i_blkbits == PAGE_SHIFT || |
| !mapping->a_ops->is_partially_uptodate) |
| goto page_not_up_to_date; |
| /* pipes can't handle partially uptodate pages */ |
| if (unlikely(iter->type & ITER_PIPE)) |
| goto page_not_up_to_date; |
| if (!trylock_page(page)) |
| goto page_not_up_to_date; |
| /* Did it get truncated before we got the lock? */ |
| if (!page->mapping) |
| goto page_not_up_to_date_locked; |
| if (!mapping->a_ops->is_partially_uptodate(page, |
| offset, iter->count)) |
| goto page_not_up_to_date_locked; |
| unlock_page(page); |
| } |
| page_ok: |
| /* |
| * i_size must be checked after we know the page is Uptodate. |
| * |
| * Checking i_size after the check allows us to calculate |
| * the correct value for "nr", which means the zero-filled |
| * part of the page is not copied back to userspace (unless |
| * another truncate extends the file - this is desired though). |
| */ |
| |
| isize = i_size_read(inode); |
| end_index = (isize - 1) >> PAGE_SHIFT; |
| if (unlikely(!isize || index > end_index)) { |
| put_page(page); |
| goto out; |
| } |
| |
| /* nr is the maximum number of bytes to copy from this page */ |
| nr = PAGE_SIZE; |
| if (index == end_index) { |
| nr = ((isize - 1) & ~PAGE_MASK) + 1; |
| if (nr <= offset) { |
| put_page(page); |
| goto out; |
| } |
| } |
| nr = nr - offset; |
| |
| /* If users can be writing to this page using arbitrary |
| * virtual addresses, take care about potential aliasing |
| * before reading the page on the kernel side. |
| */ |
| if (mapping_writably_mapped(mapping)) |
| flush_dcache_page(page); |
| |
| /* |
| * When a sequential read accesses a page several times, |
| * only mark it as accessed the first time. |
| */ |
| if (prev_index != index || offset != prev_offset) |
| mark_page_accessed(page); |
| prev_index = index; |
| |
| /* |
| * Ok, we have the page, and it's up-to-date, so |
| * now we can copy it to user space... |
| */ |
| |
| ret = copy_page_to_iter(page, offset, nr, iter); |
| offset += ret; |
| index += offset >> PAGE_SHIFT; |
| offset &= ~PAGE_MASK; |
| prev_offset = offset; |
| |
| put_page(page); |
| written += ret; |
| if (!iov_iter_count(iter)) |
| goto out; |
| if (ret < nr) { |
| error = -EFAULT; |
| goto out; |
| } |
| continue; |
| |
| page_not_up_to_date: |
| /* Get exclusive access to the page ... */ |
| error = lock_page_killable(page); |
| if (unlikely(error)) |
| goto readpage_error; |
| |
| page_not_up_to_date_locked: |
| /* Did it get truncated before we got the lock? */ |
| if (!page->mapping) { |
| unlock_page(page); |
| put_page(page); |
| continue; |
| } |
| |
| /* Did somebody else fill it already? */ |
| if (PageUptodate(page)) { |
| unlock_page(page); |
| goto page_ok; |
| } |
| |
| readpage: |
| /* |
| * A previous I/O error may have been due to temporary |
| * failures, eg. multipath errors. |
| * PG_error will be set again if readpage fails. |
| */ |
| ClearPageError(page); |
| /* Start the actual read. The read will unlock the page. */ |
| error = mapping->a_ops->readpage(filp, page); |
| |
| if (unlikely(error)) { |
| if (error == AOP_TRUNCATED_PAGE) { |
| put_page(page); |
| error = 0; |
| goto find_page; |
| } |
| goto readpage_error; |
| } |
| |
| if (!PageUptodate(page)) { |
| error = lock_page_killable(page); |
| if (unlikely(error)) |
| goto readpage_error; |
| if (!PageUptodate(page)) { |
| if (page->mapping == NULL) { |
| /* |
| * invalidate_mapping_pages got it |
| */ |
| unlock_page(page); |
| put_page(page); |
| goto find_page; |
| } |
| unlock_page(page); |
| shrink_readahead_size_eio(filp, ra); |
| error = -EIO; |
| goto readpage_error; |
| } |
| unlock_page(page); |
| } |
| |
| goto page_ok; |
| |
| readpage_error: |
| /* UHHUH! A synchronous read error occurred. Report it */ |
| put_page(page); |
| goto out; |
| |
| no_cached_page: |
| /* |
| * Ok, it wasn't cached, so we need to create a new |
| * page.. |
| */ |
| page = page_cache_alloc_cold(mapping); |
| if (!page) { |
| error = -ENOMEM; |
| goto out; |
| } |
| error = add_to_page_cache_lru(page, mapping, index, |
| mapping_gfp_constraint(mapping, GFP_KERNEL)); |
| if (error) { |
| put_page(page); |
| if (error == -EEXIST) { |
| error = 0; |
| goto find_page; |
| } |
| goto out; |
| } |
| goto readpage; |
| } |
| |
| would_block: |
| error = -EAGAIN; |
| out: |
| ra->prev_pos = prev_index; |
| ra->prev_pos <<= PAGE_SHIFT; |
| ra->prev_pos |= prev_offset; |
| |
| *ppos = ((loff_t)index << PAGE_SHIFT) + offset; |
| file_accessed(filp); |
| return written ? written : error; |
| } |
| |
| /** |
| * generic_file_read_iter - generic filesystem read routine |
| * @iocb: kernel I/O control block |
| * @iter: destination for the data read |
| * |
| * This is the "read_iter()" routine for all filesystems |
| * that can use the page cache directly. |
| */ |
| ssize_t |
| generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
| { |
| size_t count = iov_iter_count(iter); |
| ssize_t retval = 0; |
| |
| if (!count) |
| goto out; /* skip atime */ |
| |
| if (iocb->ki_flags & IOCB_DIRECT) { |
| struct file *file = iocb->ki_filp; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| loff_t size; |
| |
| size = i_size_read(inode); |
| if (iocb->ki_flags & IOCB_NOWAIT) { |
| if (filemap_range_has_page(mapping, iocb->ki_pos, |
| iocb->ki_pos + count - 1)) |
| return -EAGAIN; |
| } else { |
| retval = filemap_write_and_wait_range(mapping, |
| iocb->ki_pos, |
| iocb->ki_pos + count - 1); |
| if (retval < 0) |
| goto out; |
| } |
| |
| file_accessed(file); |
| |
| retval = mapping->a_ops->direct_IO(iocb, iter); |
| if (retval >= 0) { |
| iocb->ki_pos += retval; |
| count -= retval; |
| } |
| iov_iter_revert(iter, count - iov_iter_count(iter)); |
| |
| /* |
| * Btrfs can have a short DIO read if we encounter |
| * compressed extents, so if there was an error, or if |
| * we've already read everything we wanted to, or if |
| * there was a short read because we hit EOF, go ahead |
| * and return. Otherwise fallthrough to buffered io for |
| * the rest of the read. Buffered reads will not work for |
| * DAX files, so don't bother trying. |
| */ |
| if (retval < 0 || !count || iocb->ki_pos >= size || |
| IS_DAX(inode)) |
| goto out; |
| } |
| |
| retval = generic_file_buffered_read(iocb, iter, retval); |
| out: |
| return retval; |
| } |
| EXPORT_SYMBOL(generic_file_read_iter); |
| |
| #ifdef CONFIG_MMU |
| #define MMAP_LOTSAMISS (100) |
| static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, |
| struct file *fpin) |
| { |
| int flags = vmf->flags; |
| |
| if (fpin) |
| return fpin; |
| |
| /* |
| * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or |
| * anything, so we only pin the file and drop the mmap_sem if only |
| * FAULT_FLAG_ALLOW_RETRY is set. |
| */ |
| if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) == |
| FAULT_FLAG_ALLOW_RETRY) { |
| fpin = get_file(vmf->vma->vm_file); |
| up_read(&vmf->vma->vm_mm->mmap_sem); |
| } |
| return fpin; |
| } |
| |
| /* |
| * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_sem |
| * @vmf - the vm_fault for this fault. |
| * @page - the page to lock. |
| * @fpin - the pointer to the file we may pin (or is already pinned). |
| * |
| * This works similar to lock_page_or_retry in that it can drop the mmap_sem. |
| * It differs in that it actually returns the page locked if it returns 1 and 0 |
| * if it couldn't lock the page. If we did have to drop the mmap_sem then fpin |
| * will point to the pinned file and needs to be fput()'ed at a later point. |
| */ |
| static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page, |
| struct file **fpin) |
| { |
| if (trylock_page(page)) |
| return 1; |
| |
| /* |
| * NOTE! This will make us return with VM_FAULT_RETRY, but with |
| * the mmap_sem still held. That's how FAULT_FLAG_RETRY_NOWAIT |
| * is supposed to work. We have way too many special cases.. |
| */ |
| if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
| return 0; |
| |
| *fpin = maybe_unlock_mmap_for_io(vmf, *fpin); |
| if (vmf->flags & FAULT_FLAG_KILLABLE) { |
| if (__lock_page_killable(page)) { |
| /* |
| * We didn't have the right flags to drop the mmap_sem, |
| * but all fault_handlers only check for fatal signals |
| * if we return VM_FAULT_RETRY, so we need to drop the |
| * mmap_sem here and return 0 if we don't have a fpin. |
| */ |
| if (*fpin == NULL) |
| up_read(&vmf->vma->vm_mm->mmap_sem); |
| return 0; |
| } |
| } else |
| __lock_page(page); |
| return 1; |
| } |
| |
| |
| /* |
| * Synchronous readahead happens when we don't even find a page in the page |
| * cache at all. We don't want to perform IO under the mmap sem, so if we have |
| * to drop the mmap sem we return the file that was pinned in order for us to do |
| * that. If we didn't pin a file then we return NULL. The file that is |
| * returned needs to be fput()'ed when we're done with it. |
| */ |
| static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) |
| { |
| struct file *file = vmf->vma->vm_file; |
| struct file_ra_state *ra = &file->f_ra; |
| struct address_space *mapping = file->f_mapping; |
| struct file *fpin = NULL; |
| pgoff_t offset = vmf->pgoff; |
| |
| /* If we don't want any read-ahead, don't bother */ |
| if (vmf->vma->vm_flags & VM_RAND_READ) |
| return fpin; |
| if (!ra->ra_pages) |
| return fpin; |
| |
| if (vmf->vma->vm_flags & VM_SEQ_READ) { |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| page_cache_sync_readahead(mapping, ra, file, offset, |
| ra->ra_pages); |
| return fpin; |
| } |
| |
| /* Avoid banging the cache line if not needed */ |
| if (ra->mmap_miss < MMAP_LOTSAMISS * 10) |
| ra->mmap_miss++; |
| |
| /* |
| * Do we miss much more than hit in this file? If so, |
| * stop bothering with read-ahead. It will only hurt. |
| */ |
| if (ra->mmap_miss > MMAP_LOTSAMISS) |
| return fpin; |
| |
| /* |
| * mmap read-around |
| */ |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| ra->start = max_t(long, 0, offset - ra->ra_pages / 2); |
| ra->size = ra->ra_pages; |
| ra->async_size = ra->ra_pages / 4; |
| ra_submit(ra, mapping, file); |
| return fpin; |
| } |
| |
| /* |
| * Asynchronous readahead happens when we find the page and PG_readahead, |
| * so we want to possibly extend the readahead further. We return the file that |
| * was pinned if we have to drop the mmap_sem in order to do IO. |
| */ |
| static struct file *do_async_mmap_readahead(struct vm_fault *vmf, |
| struct page *page) |
| { |
| struct file *file = vmf->vma->vm_file; |
| struct file_ra_state *ra = &file->f_ra; |
| struct address_space *mapping = file->f_mapping; |
| struct file *fpin = NULL; |
| pgoff_t offset = vmf->pgoff; |
| |
| /* If we don't want any read-ahead, don't bother */ |
| if (vmf->vma->vm_flags & VM_RAND_READ) |
| return fpin; |
| if (ra->mmap_miss > 0) |
| ra->mmap_miss--; |
| if (PageReadahead(page)) { |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| page_cache_async_readahead(mapping, ra, file, |
| page, offset, ra->ra_pages); |
| } |
| return fpin; |
| } |
| |
| /** |
| * filemap_fault - read in file data for page fault handling |
| * @vmf: struct vm_fault containing details of the fault |
| * |
| * filemap_fault() is invoked via the vma operations vector for a |
| * mapped memory region to read in file data during a page fault. |
| * |
| * The goto's are kind of ugly, but this streamlines the normal case of having |
| * it in the page cache, and handles the special cases reasonably without |
| * having a lot of duplicated code. |
| * |
| * vma->vm_mm->mmap_sem must be held on entry. |
| * |
| * If our return value has VM_FAULT_RETRY set, it's because |
| * lock_page_or_retry() returned 0. |
| * The mmap_sem has usually been released in this case. |
| * See __lock_page_or_retry() for the exception. |
| * |
| * If our return value does not have VM_FAULT_RETRY set, the mmap_sem |
| * has not been released. |
| * |
| * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. |
| */ |
| int filemap_fault(struct vm_fault *vmf) |
| { |
| int error; |
| struct file *file = vmf->vma->vm_file; |
| struct file *fpin = NULL; |
| struct address_space *mapping = file->f_mapping; |
| struct file_ra_state *ra = &file->f_ra; |
| struct inode *inode = mapping->host; |
| pgoff_t offset = vmf->pgoff; |
| pgoff_t max_off; |
| struct page *page; |
| int ret = 0; |
| |
| max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| if (unlikely(offset >= max_off)) |
| return VM_FAULT_SIGBUS; |
| |
| /* |
| * Do we have something in the page cache already? |
| */ |
| page = find_get_page(mapping, offset); |
| if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { |
| /* |
| * We found the page, so try async readahead before |
| * waiting for the lock. |
| */ |
| fpin = do_async_mmap_readahead(vmf, page); |
| } else if (!page) { |
| /* No page in the page cache at all */ |
| count_vm_event(PGMAJFAULT); |
| count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); |
| ret = VM_FAULT_MAJOR; |
| fpin = do_sync_mmap_readahead(vmf); |
| retry_find: |
| page = pagecache_get_page(mapping, offset, |
| FGP_CREAT|FGP_FOR_MMAP, |
| vmf->gfp_mask); |
| if (!page) { |
| if (fpin) |
| goto out_retry; |
| return VM_FAULT_OOM; |
| } |
| } |
| |
| if (!lock_page_maybe_drop_mmap(vmf, page, &fpin)) |
| goto out_retry; |
| |
| /* Did it get truncated? */ |
| if (unlikely(page->mapping != mapping)) { |
| unlock_page(page); |
| put_page(page); |
| goto retry_find; |
| } |
| VM_BUG_ON_PAGE(page->index != offset, page); |
| |
| /* |
| * We have a locked page in the page cache, now we need to check |
| * that it's up-to-date. If not, it is going to be due to an error. |
| */ |
| if (unlikely(!PageUptodate(page))) |
| goto page_not_uptodate; |
| |
| /* |
| * We've made it this far and we had to drop our mmap_sem, now is the |
| * time to return to the upper layer and have it re-find the vma and |
| * redo the fault. |
| */ |
| if (fpin) { |
| unlock_page(page); |
| goto out_retry; |
| } |
| |
| /* |
| * Found the page and have a reference on it. |
| * We must recheck i_size under page lock. |
| */ |
| max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| if (unlikely(offset >= max_off)) { |
| unlock_page(page); |
| put_page(page); |
| return VM_FAULT_SIGBUS; |
| } |
| |
| vmf->page = page; |
| return ret | VM_FAULT_LOCKED; |
| |
| page_not_uptodate: |
| /* |
| * Umm, take care of errors if the page isn't up-to-date. |
| * Try to re-read it _once_. We do this synchronously, |
| * because there really aren't any performance issues here |
| * and we need to check for errors. |
| */ |
| ClearPageError(page); |
| fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| error = mapping->a_ops->readpage(file, page); |
| if (!error) { |
| wait_on_page_locked(page); |
| if (!PageUptodate(page)) |
| error = -EIO; |
| } |
| if (fpin) |
| goto out_retry; |
| put_page(page); |
| |
| if (!error || error == AOP_TRUNCATED_PAGE) |
| goto retry_find; |
| |
| /* Things didn't work out. Return zero to tell the mm layer so. */ |
| shrink_readahead_size_eio(file, ra); |
| return VM_FAULT_SIGBUS; |
| |
| out_retry: |
| /* |
| * We dropped the mmap_sem, we need to return to the fault handler to |
| * re-find the vma and come back and find our hopefully still populated |
| * page. |
| */ |
| if (page) |
| put_page(page); |
| if (fpin) |
| fput(fpin); |
| return ret | VM_FAULT_RETRY; |
| } |
| EXPORT_SYMBOL(filemap_fault); |
| |
| void filemap_map_pages(struct vm_fault *vmf, |
| pgoff_t start_pgoff, pgoff_t end_pgoff) |
| { |
| struct radix_tree_iter iter; |
| void **slot; |
| struct file *file = vmf->vma->vm_file; |
| struct address_space *mapping = file->f_mapping; |
| pgoff_t last_pgoff = start_pgoff; |
| unsigned long max_idx; |
| struct page *head, *page; |
| |
| rcu_read_lock(); |
| radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, |
| start_pgoff) { |
| if (iter.index > end_pgoff) |
| break; |
| repeat: |
| page = radix_tree_deref_slot(slot); |
| if (unlikely(!page)) |
| goto next; |
| if (radix_tree_exception(page)) { |
| if (radix_tree_deref_retry(page)) { |
| slot = radix_tree_iter_retry(&iter); |
| continue; |
| } |
| goto next; |
| } |
| |
| head = compound_head(page); |
| if (!page_cache_get_speculative(head)) |
| goto repeat; |
| |
| /* The page was split under us? */ |
| if (compound_head(page) != head) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| /* Has the page moved? */ |
| if (unlikely(page != *slot)) { |
| put_page(head); |
| goto repeat; |
| } |
| |
| if (!PageUptodate(page) || |
| PageReadahead(page) || |
| PageHWPoison(page)) |
| goto skip; |
| if (!trylock_page(page)) |
| goto skip; |
| |
| if (page->mapping != mapping || !PageUptodate(page)) |
| goto unlock; |
| |
| max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); |
| if (page->index >= max_idx) |
| goto unlock; |
| |
| if (file->f_ra.mmap_miss > 0) |
| file->f_ra.mmap_miss--; |
| |
| vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT; |
| if (vmf->pte) |
| vmf->pte += iter.index - last_pgoff; |
| last_pgoff = iter.index; |
| if (alloc_set_pte(vmf, NULL, page)) |
| goto unlock; |
| unlock_page(page); |
| goto next; |
| unlock: |
| unlock_page(page); |
| skip: |
| put_page(page); |
| next: |
| /* Huge page is mapped? No need to proceed. */ |
| if (pmd_trans_huge(*vmf->pmd)) |
| break; |
| if (iter.index == end_pgoff) |
| break; |
| } |
| rcu_read_unlock(); |
| } |
| EXPORT_SYMBOL(filemap_map_pages); |
| |
| int filemap_page_mkwrite(struct vm_fault *vmf) |
| { |
| struct page *page = vmf->page; |
| struct inode *inode = file_inode(vmf->vma->vm_file); |
| int ret = VM_FAULT_LOCKED; |
| |
| sb_start_pagefault(inode->i_sb); |
| file_update_time(vmf->vma->vm_file); |
| lock_page(page); |
| if (page->mapping != inode->i_mapping) { |
| unlock_page(page); |
| ret = VM_FAULT_NOPAGE; |
| goto out; |
| } |
| /* |
| * We mark the page dirty already here so that when freeze is in |
| * progress, we are guaranteed that writeback during freezing will |
| * see the dirty page and writeprotect it again. |
| */ |
| set_page_dirty(page); |
| wait_for_stable_page(page); |
| out: |
| sb_end_pagefault(inode->i_sb); |
| return ret; |
| } |
| EXPORT_SYMBOL(filemap_page_mkwrite); |
| |
| const struct vm_operations_struct generic_file_vm_ops = { |
| .fault = filemap_fault, |
| .map_pages = filemap_map_pages, |
| .page_mkwrite = filemap_page_mkwrite, |
| }; |
| |
| /* This is used for a general mmap of a disk file */ |
| |
| int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
| { |
| struct address_space *mapping = file->f_mapping; |
| |
| if (!mapping->a_ops->readpage) |
| return -ENOEXEC; |
| file_accessed(file); |
| vma->vm_ops = &generic_file_vm_ops; |
| return 0; |
| } |
| |
| /* |
| * This is for filesystems which do not implement ->writepage. |
| */ |
| int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
| { |
| if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
| return -EINVAL; |
| return generic_file_mmap(file, vma); |
| } |
| #else |
| int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
| { |
| return -ENOSYS; |
| } |
| int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) |
| { |
| return -ENOSYS; |
| } |
| #endif /* CONFIG_MMU */ |
| |
| EXPORT_SYMBOL(generic_file_mmap); |
| EXPORT_SYMBOL(generic_file_readonly_mmap); |
| |
| static struct page *wait_on_page_read(struct page *page) |
| { |
| if (!IS_ERR(page)) { |
| wait_on_page_locked(page); |
| if (!PageUptodate(page)) { |
| put_page(page); |
| page = ERR_PTR(-EIO); |
| } |
| } |
| return page; |
| } |
| |
| static struct page *do_read_cache_page(struct address_space *mapping, |
| pgoff_t index, |
| int (*filler)(struct file *, struct page *), |
| void *data, |
| gfp_t gfp) |
| { |
| struct page *page; |
| int err; |
| repeat: |
| page = find_get_page(mapping, index); |
| if (!page) { |
| page = __page_cache_alloc(gfp | __GFP_COLD); |
| if (!page) |
| return ERR_PTR(-ENOMEM); |
| err = add_to_page_cache_lru(page, mapping, index, gfp); |
| if (unlikely(err)) { |
| put_page(page); |
| if (err == -EEXIST) |
| goto repeat; |
| /* Presumably ENOMEM for radix tree node */ |
| return ERR_PTR(err); |
| } |
| |
| filler: |
| err = filler(data, page); |
| if (err < 0) { |
| put_page(page); |
| return ERR_PTR(err); |
| } |
| |
| page = wait_on_page_read(page); |
| if (IS_ERR(page)) |
| return page; |
| goto out; |
| } |
| if (PageUptodate(page)) |
| goto out; |
| |
| /* |
| * Page is not up to date and may be locked due one of the following |
| * case a: Page is being filled and the page lock is held |
| * case b: Read/write error clearing the page uptodate status |
| * case c: Truncation in progress (page locked) |
| * case d: Reclaim in progress |
| * |
| * Case a, the page will be up to date when the page is unlocked. |
| * There is no need to serialise on the page lock here as the page |
| * is pinned so the lock gives no additional protection. Even if the |
| * the page is truncated, the data is still valid if PageUptodate as |
| * it's a race vs truncate race. |
| * Case b, the page will not be up to date |
| * Case c, the page may be truncated but in itself, the data may still |
| * be valid after IO completes as it's a read vs truncate race. The |
| * operation must restart if the page is not uptodate on unlock but |
| * otherwise serialising on page lock to stabilise the mapping gives |
| * no additional guarantees to the caller as the page lock is |
| * released before return. |
| * Case d, similar to truncation. If reclaim holds the page lock, it |
| * will be a race with remove_mapping that determines if the mapping |
| * is valid on unlock but otherwise the data is valid and there is |
| * no need to serialise with page lock. |
| * |
| * As the page lock gives no additional guarantee, we optimistically |
| * wait on the page to be unlocked and check if it's up to date and |
| * use the page if it is. Otherwise, the page lock is required to |
| * distinguish between the different cases. The motivation is that we |
| * avoid spurious serialisations and wakeups when multiple processes |
| * wait on the same page for IO to complete. |
| */ |
| wait_on_page_locked(page); |
| if (PageUptodate(page)) |
| goto out; |
| |
| /* Distinguish between all the cases under the safety of the lock */ |
| lock_page(page); |
| |
| /* Case c or d, restart the operation */ |
| if (!page->mapping) { |
| unlock_page(page); |
| put_page(page); |
| goto repeat; |
| } |
| |
| /* Someone else locked and filled the page in a very small window */ |
| if (PageUptodate(page)) { |
| unlock_page(page); |
| goto out; |
| } |
| goto filler; |
| |
| out: |
| mark_page_accessed(page); |
| return page; |
| } |
| |
| /** |
| * read_cache_page - read into page cache, fill it if needed |
| * @mapping: the page's address_space |
| * @index: the page index |
| * @filler: function to perform the read |
| * @data: first arg to filler(data, page) function, often left as NULL |
| * |
| * Read into the page cache. If a page already exists, and PageUptodate() is |
| * not set, try to fill the page and wait for it to become unlocked. |
| * |
| * If the page does not get brought uptodate, return -EIO. |
| */ |
| struct page *read_cache_page(struct address_space *mapping, |
| pgoff_t index, |
| int (*filler)(struct file *, struct page *), |
| void *data) |
| { |
| return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); |
| } |
| EXPORT_SYMBOL(read_cache_page); |
| |
| /** |
| * read_cache_page_gfp - read into page cache, using specified page allocation flags. |
| * @mapping: the page's address_space |
| * @index: the page index |
| * @gfp: the page allocator flags to use if allocating |
| * |
| * This is the same as "read_mapping_page(mapping, index, NULL)", but with |
| * any new page allocations done using the specified allocation flags. |
| * |
| * If the page does not get brought uptodate, return -EIO. |
| */ |
| struct page *read_cache_page_gfp(struct address_space *mapping, |
| pgoff_t index, |
| gfp_t gfp) |
| { |
| filler_t *filler = mapping->a_ops->readpage; |
| |
| return do_read_cache_page(mapping, index, filler, NULL, gfp); |
| } |
| EXPORT_SYMBOL(read_cache_page_gfp); |
| |
| /* |
| * Performs necessary checks before doing a write |
| * |
| * Can adjust writing position or amount of bytes to write. |
| * Returns appropriate error code that caller should return or |
| * zero in case that write should be allowed. |
| */ |
| inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) |
| { |
| struct file *file = iocb->ki_filp; |
| struct inode *inode = file->f_mapping->host; |
| unsigned long limit = rlimit(RLIMIT_FSIZE); |
| loff_t pos; |
| |
| if (!iov_iter_count(from)) |
| return 0; |
| |
| /* FIXME: this is for backwards compatibility with 2.4 */ |
| if (iocb->ki_flags & IOCB_APPEND) |
| iocb->ki_pos = i_size_read(inode); |
| |
| pos = iocb->ki_pos; |
| |
| if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) |
| return -EINVAL; |
| |
| if (limit != RLIM_INFINITY) { |
| if (iocb->ki_pos >= limit) { |
| send_sig(SIGXFSZ, current, 0); |
| return -EFBIG; |
| } |
| iov_iter_truncate(from, limit - (unsigned long)pos); |
| } |
| |
| /* |
| * LFS rule |
| */ |
| if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS && |
| !(file->f_flags & O_LARGEFILE))) { |
| if (pos >= MAX_NON_LFS) |
| return -EFBIG; |
| iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos); |
| } |
| |
| /* |
| * Are we about to exceed the fs block limit ? |
| * |
| * If we have written data it becomes a short write. If we have |
| * exceeded without writing data we send a signal and return EFBIG. |
| * Linus frestrict idea will clean these up nicely.. |
| */ |
| if (unlikely(pos >= inode->i_sb->s_maxbytes)) |
| return -EFBIG; |
| |
| iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos); |
| return iov_iter_count(from); |
| } |
| EXPORT_SYMBOL(generic_write_checks); |
| |
| int pagecache_write_begin(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned flags, |
| struct page **pagep, void **fsdata) |
| { |
| const struct address_space_operations *aops = mapping->a_ops; |
| |
| return aops->write_begin(file, mapping, pos, len, flags, |
| pagep, fsdata); |
| } |
| EXPORT_SYMBOL(pagecache_write_begin); |
| |
| int pagecache_write_end(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned copied, |
| struct page *page, void *fsdata) |
| { |
| const struct address_space_operations *aops = mapping->a_ops; |
| |
| return aops->write_end(file, mapping, pos, len, copied, page, fsdata); |
| } |
| EXPORT_SYMBOL(pagecache_write_end); |
| |
| ssize_t |
| generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) |
| { |
| struct file *file = iocb->ki_filp; |
| struct address_space *mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| loff_t pos = iocb->ki_pos; |
| ssize_t written; |
| size_t write_len; |
| pgoff_t end; |
| |
| write_len = iov_iter_count(from); |
| end = (pos + write_len - 1) >> PAGE_SHIFT; |
| |
| if (iocb->ki_flags & IOCB_NOWAIT) { |
| /* If there are pages to writeback, return */ |
| if (filemap_range_has_page(inode->i_mapping, pos, |
| pos + iov_iter_count(from))) |
| return -EAGAIN; |
| } else { |
| written = filemap_write_and_wait_range(mapping, pos, |
| pos + write_len - 1); |
| if (written) |
| goto out; |
| } |
| |
| /* |
| * After a write we want buffered reads to be sure to go to disk to get |
| * the new data. We invalidate clean cached page from the region we're |
| * about to write. We do this *before* the write so that we can return |
| * without clobbering -EIOCBQUEUED from ->direct_IO(). |
| */ |
| written = invalidate_inode_pages2_range(mapping, |
| pos >> PAGE_SHIFT, end); |
| /* |
| * If a page can not be invalidated, return 0 to fall back |
| * to buffered write. |
| */ |
| if (written) { |
| if (written == -EBUSY) |
| return 0; |
| goto out; |
| } |
| |
| written = mapping->a_ops->direct_IO(iocb, from); |
| |
| /* |
| * Finally, try again to invalidate clean pages which might have been |
| * cached by non-direct readahead, or faulted in by get_user_pages() |
| * if the source of the write was an mmap'ed region of the file |
| * we're writing. Either one is a pretty crazy thing to do, |
| * so we don't support it 100%. If this invalidation |
| * fails, tough, the write still worked... |
| * |
| * Most of the time we do not need this since dio_complete() will do |
| * the invalidation for us. However there are some file systems that |
| * do not end up with dio_complete() being called, so let's not break |
| * them by removing it completely |
| */ |
| if (mapping->nrpages) |
| invalidate_inode_pages2_range(mapping, |
| pos >> PAGE_SHIFT, end); |
| |
| if (written > 0) { |
| pos += written; |
| write_len -= written; |
| if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
| i_size_write(inode, pos); |
| mark_inode_dirty(inode); |
| } |
| iocb->ki_pos = pos; |
| } |
| iov_iter_revert(from, write_len - iov_iter_count(from)); |
| out: |
| return written; |
| } |
| EXPORT_SYMBOL(generic_file_direct_write); |
| |
| /* |
| * Find or create a page at the given pagecache position. Return the locked |
| * page. This function is specifically for buffered writes. |
| */ |
| struct page *grab_cache_page_write_begin(struct address_space *mapping, |
| pgoff_t index, unsigned flags) |
| { |
| struct page *page; |
| int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; |
| |
| if (flags & AOP_FLAG_NOFS) |
| fgp_flags |= FGP_NOFS; |
| |
| page = pagecache_get_page(mapping, index, fgp_flags, |
| mapping_gfp_mask(mapping)); |
| if (page) |
| wait_for_stable_page(page); |
| |
| return page; |
| } |
| EXPORT_SYMBOL(grab_cache_page_write_begin); |
| |
| ssize_t generic_perform_write(struct file *file, |
| struct iov_iter *i, loff_t pos) |
| { |
| struct address_space *mapping = file->f_mapping; |
| const struct address_space_operations *a_ops = mapping->a_ops; |
| long status = 0; |
| ssize_t written = 0; |
| unsigned int flags = 0; |
| |
| do { |
| struct page *page; |
| unsigned long offset; /* Offset into pagecache page */ |
| unsigned long bytes; /* Bytes to write to page */ |
| size_t copied; /* Bytes copied from user */ |
| void *fsdata; |
| |
| offset = (pos & (PAGE_SIZE - 1)); |
| bytes = min_t(unsigned long, PAGE_SIZE - offset, |
| iov_iter_count(i)); |
| |
| again: |
| /* |
| * Bring in the user page that we will copy from _first_. |
| * Otherwise there's a nasty deadlock on copying from the |
| * same page as we're writing to, without it being marked |
| * up-to-date. |
| * |
| * Not only is this an optimisation, but it is also required |
| * to check that the address is actually valid, when atomic |
| * usercopies are used, below. |
| */ |
| if (unlikely(iov_iter_fault_in_readable(i, bytes))) { |
| status = -EFAULT; |
| break; |
| } |
| |
| if (fatal_signal_pending(current)) { |
| status = -EINTR; |
| break; |
| } |
| |
| status = a_ops->write_begin(file, mapping, pos, bytes, flags, |
| &page, &fsdata); |
| if (unlikely(status < 0)) |
| break; |
| |
| if (mapping_writably_mapped(mapping)) |
| flush_dcache_page(page); |
| |
| copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); |
| flush_dcache_page(page); |
| |
| status = a_ops->write_end(file, mapping, pos, bytes, copied, |
| page, fsdata); |
| if (unlikely(status < 0)) |
| break; |
| copied = status; |
| |
| cond_resched(); |
| |
| iov_iter_advance(i, copied); |
| if (unlikely(copied == 0)) { |
| /* |
| * If we were unable to copy any data at all, we must |
| * fall back to a single segment length write. |
| * |
| * If we didn't fallback here, we could livelock |
| * because not all segments in the iov can be copied at |
| * once without a pagefault. |
| */ |
| bytes = min_t(unsigned long, PAGE_SIZE - offset, |
| iov_iter_single_seg_count(i)); |
| goto again; |
| } |
| pos += copied; |
| written += copied; |
| |
| balance_dirty_pages_ratelimited(mapping); |
| } while (iov_iter_count(i)); |
| |
| return written ? written : status; |
| } |
| EXPORT_SYMBOL(generic_perform_write); |
| |
| /** |
| * __generic_file_write_iter - write data to a file |
| * @iocb: IO state structure (file, offset, etc.) |
| * @from: iov_iter with data to write |
| * |
| * This function does all the work needed for actually writing data to a |
| * file. It does all basic checks, removes SUID from the file, updates |
| * modification times and calls proper subroutines depending on whether we |
| * do direct IO or a standard buffered write. |
| * |
| * It expects i_mutex to be grabbed unless we work on a block device or similar |
| * object which does not need locking at all. |
| * |
| * This function does *not* take care of syncing data in case of O_SYNC write. |
| * A caller has to handle it. This is mainly due to the fact that we want to |
| * avoid syncing under i_mutex. |
| */ |
| ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
| { |
| struct file *file = iocb->ki_filp; |
| struct address_space * mapping = file->f_mapping; |
| struct inode *inode = mapping->host; |
| ssize_t written = 0; |
| ssize_t err; |
| ssize_t status; |
| |
| /* We can write back this queue in page reclaim */ |
| current->backing_dev_info = inode_to_bdi(inode); |
| err = file_remove_privs(file); |
| if (err) |
| goto out; |
| |
| err = file_update_time(file); |
| if (err) |
| goto out; |
| |
| if (iocb->ki_flags & IOCB_DIRECT) { |
| loff_t pos, endbyte; |
| |
| written = generic_file_direct_write(iocb, from); |
| /* |
| * If the write stopped short of completing, fall back to |
| * buffered writes. Some filesystems do this for writes to |
| * holes, for example. For DAX files, a buffered write will |
| * not succeed (even if it did, DAX does not handle dirty |
| * page-cache pages correctly). |
| */ |
| if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) |
| goto out; |
| |
| status = generic_perform_write(file, from, pos = iocb->ki_pos); |
| /* |
| * If generic_perform_write() returned a synchronous error |
| * then we want to return the number of bytes which were |
| * direct-written, or the error code if that was zero. Note |
| * that this differs from normal direct-io semantics, which |
| * will return -EFOO even if some bytes were written. |
| */ |
| if (unlikely(status < 0)) { |
| err = status; |
| goto out; |
| } |
| /* |
| * We need to ensure that the page cache pages are written to |
| * disk and invalidated to preserve the expected O_DIRECT |
| * semantics. |
| */ |
| endbyte = pos + status - 1; |
| err = filemap_write_and_wait_range(mapping, pos, endbyte); |
| if (err == 0) { |
| iocb->ki_pos = endbyte + 1; |
| written += status; |
| invalidate_mapping_pages(mapping, |
| pos >> PAGE_SHIFT, |
| endbyte >> PAGE_SHIFT); |
| } else { |
| /* |
| * We don't know how much we wrote, so just return |
| * the number of bytes which were direct-written |
| */ |
| } |
| } else { |
| written = generic_perform_write(file, from, iocb->ki_pos); |
| if (likely(written > 0)) |
| iocb->ki_pos += written; |
| } |
| out: |
| current->backing_dev_info = NULL; |
| return written ? written : err; |
| } |
| EXPORT_SYMBOL(__generic_file_write_iter); |
| |
| /** |
| * generic_file_write_iter - write data to a file |
| * @iocb: IO state structure |
| * @from: iov_iter with data to write |
| * |
| * This is a wrapper around __generic_file_write_iter() to be used by most |
| * filesystems. It takes care of syncing the file in case of O_SYNC file |
| * and acquires i_mutex as needed. |
| */ |
| ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
| { |
| struct file *file = iocb->ki_filp; |
| struct inode *inode = file->f_mapping->host; |
| ssize_t ret; |
| |
| inode_lock(inode); |
| ret = generic_write_checks(iocb, from); |
| if (ret > 0) |
| ret = __generic_file_write_iter(iocb, from); |
| inode_unlock(inode); |
| |
| if (ret > 0) |
| ret = generic_write_sync(iocb, ret); |
| return ret; |
| } |
| EXPORT_SYMBOL(generic_file_write_iter); |
| |
| /** |
| * try_to_release_page() - release old fs-specific metadata on a page |
| * |
| * @page: the page which the kernel is trying to free |
| * @gfp_mask: memory allocation flags (and I/O mode) |
| * |
| * The address_space is to try to release any data against the page |
| * (presumably at page->private). If the release was successful, return '1'. |
| * Otherwise return zero. |
| * |
| * This may also be called if PG_fscache is set on a page, indicating that the |
| * page is known to the local caching routines. |
| * |
| * The @gfp_mask argument specifies whether I/O may be performed to release |
| * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS). |
| * |
| */ |
| int try_to_release_page(struct page *page, gfp_t gfp_mask) |
| { |
| struct address_space * const mapping = page->mapping; |
| |
| BUG_ON(!PageLocked(page)); |
| if (PageWriteback(page)) |
| return 0; |
| |
| if (mapping && mapping->a_ops->releasepage) |
| return mapping->a_ops->releasepage(page, gfp_mask); |
| return try_to_free_buffers(page); |
| } |
| |
| EXPORT_SYMBOL(try_to_release_page); |