iomap: use a srcmap for a read-modify-write I/O
The srcmap is used to identify where the read is to be performed from.
It is passed to ->iomap_begin, which can fill it in if we need to read
data for partially written blocks from a different location than the
write target. The srcmap is only supported for buffered writes so far.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
[hch: merged two patches, removed the IOMAP_F_COW flag, use iomap as
srcmap if not set, adjust length down to srcmap end as well]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
diff --git a/fs/dax.c b/fs/dax.c
index 6bf81f9..68eef98 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1090,7 +1090,7 @@
static loff_t
dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct block_device *bdev = iomap->bdev;
struct dax_device *dax_dev = iomap->dax_dev;
@@ -1247,7 +1247,8 @@
struct inode *inode = mapping->host;
unsigned long vaddr = vmf->address;
loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
- struct iomap iomap = { 0 };
+ struct iomap iomap = { .type = IOMAP_HOLE };
+ struct iomap srcmap = { .type = IOMAP_HOLE };
unsigned flags = IOMAP_FAULT;
int error, major = 0;
bool write = vmf->flags & FAULT_FLAG_WRITE;
@@ -1292,7 +1293,7 @@
* the file system block size to be equal the page size, which means
* that we never have to deal with more than a single extent here.
*/
- error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
+ error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap, &srcmap);
if (iomap_errp)
*iomap_errp = error;
if (error) {
@@ -1471,7 +1472,8 @@
unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
struct inode *inode = mapping->host;
vm_fault_t result = VM_FAULT_FALLBACK;
- struct iomap iomap = { 0 };
+ struct iomap iomap = { .type = IOMAP_HOLE };
+ struct iomap srcmap = { .type = IOMAP_HOLE };
pgoff_t max_pgoff;
void *entry;
loff_t pos;
@@ -1546,7 +1548,8 @@
* to look up our filesystem block.
*/
pos = (loff_t)xas.xa_index << PAGE_SHIFT;
- error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+ error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap,
+ &srcmap);
if (error)
goto unlock_entry;
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 7004ce5..467c13f 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -801,7 +801,7 @@
#ifdef CONFIG_FS_DAX
static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
- unsigned flags, struct iomap *iomap)
+ unsigned flags, struct iomap *iomap, struct iomap *srcmap)
{
unsigned int blkbits = inode->i_blkbits;
unsigned long first_block = offset >> blkbits;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 516faa2..abaaf7d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3407,7 +3407,7 @@
}
static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
- unsigned flags, struct iomap *iomap)
+ unsigned flags, struct iomap *iomap, struct iomap *srcmap)
{
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
unsigned int blkbits = inode->i_blkbits;
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index f63df54..5161032 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1149,7 +1149,8 @@
}
static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
- unsigned flags, struct iomap *iomap)
+ unsigned flags, struct iomap *iomap,
+ struct iomap *srcmap)
{
struct gfs2_inode *ip = GFS2_I(inode);
struct metapath mp = { .mp_aheight = 1, };
diff --git a/fs/iomap/apply.c b/fs/iomap/apply.c
index 54c02ae..484dd8e 100644
--- a/fs/iomap/apply.c
+++ b/fs/iomap/apply.c
@@ -23,8 +23,10 @@
iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
const struct iomap_ops *ops, void *data, iomap_actor_t actor)
{
- struct iomap iomap = { 0 };
+ struct iomap iomap = { .type = IOMAP_HOLE };
+ struct iomap srcmap = { .type = IOMAP_HOLE };
loff_t written = 0, ret;
+ u64 end;
/*
* Need to map a range from start position for length bytes. This can
@@ -38,7 +40,7 @@
* expose transient stale data. If the reserve fails, we can safely
* back out at this point as there is nothing to undo.
*/
- ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
+ ret = ops->iomap_begin(inode, pos, length, flags, &iomap, &srcmap);
if (ret)
return ret;
if (WARN_ON(iomap.offset > pos))
@@ -50,15 +52,26 @@
* Cut down the length to the one actually provided by the filesystem,
* as it might not be able to give us the whole size that we requested.
*/
- if (iomap.offset + iomap.length < pos + length)
- length = iomap.offset + iomap.length - pos;
+ end = iomap.offset + iomap.length;
+ if (srcmap.type != IOMAP_HOLE)
+ end = min(end, srcmap.offset + srcmap.length);
+ if (pos + length > end)
+ length = end - pos;
/*
- * Now that we have guaranteed that the space allocation will succeed.
+ * Now that we have guaranteed that the space allocation will succeed,
* we can do the copy-in page by page without having to worry about
* failures exposing transient data.
+ *
+ * To support COW operations, we read in data for partially blocks from
+ * the srcmap if the file system filled it in. In that case we the
+ * length needs to be limited to the earlier of the ends of the iomaps.
+ * If the file system did not provide a srcmap we pass in the normal
+ * iomap into the actors so that they don't need to have special
+ * handling for the two cases.
*/
- written = actor(inode, pos, length, data, &iomap);
+ written = actor(inode, pos, length, data, &iomap,
+ srcmap.type != IOMAP_HOLE ? &srcmap : &iomap);
/*
* Now the data has been copied, commit the range we've copied. This
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index b610768..c62e8079 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -234,7 +234,7 @@
static loff_t
iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct iomap_readpage_ctx *ctx = data;
struct page *page = ctx->cur_page;
@@ -382,7 +382,7 @@
static loff_t
iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
struct iomap_readpage_ctx *ctx = data;
loff_t done, ret;
@@ -402,7 +402,7 @@
ctx->cur_page_in_bio = false;
}
ret = iomap_readpage_actor(inode, pos + done, length - done,
- ctx, iomap);
+ ctx, iomap, srcmap);
}
return done;
@@ -582,7 +582,7 @@
static int
__iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
- struct page *page, struct iomap *iomap)
+ struct page *page, struct iomap *srcmap)
{
struct iomap_page *iop = iomap_page_create(inode, page);
loff_t block_size = i_blocksize(inode);
@@ -605,7 +605,7 @@
(to <= poff || to >= poff + plen))
continue;
- if (iomap_block_needs_zeroing(inode, iomap, block_start)) {
+ if (iomap_block_needs_zeroing(inode, srcmap, block_start)) {
if (WARN_ON_ONCE(flags & IOMAP_WRITE_F_UNSHARE))
return -EIO;
zero_user_segments(page, poff, from, to, poff + plen);
@@ -614,7 +614,7 @@
}
status = iomap_read_page_sync(block_start, page, poff, plen,
- iomap);
+ srcmap);
if (status)
return status;
} while ((block_start += plen) < block_end);
@@ -624,13 +624,15 @@
static int
iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
- struct page **pagep, struct iomap *iomap)
+ struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
{
const struct iomap_page_ops *page_ops = iomap->page_ops;
struct page *page;
int status = 0;
BUG_ON(pos + len > iomap->offset + iomap->length);
+ if (srcmap != iomap)
+ BUG_ON(pos + len > srcmap->offset + srcmap->length);
if (fatal_signal_pending(current))
return -EINTR;
@@ -648,13 +650,13 @@
goto out_no_page;
}
- if (iomap->type == IOMAP_INLINE)
- iomap_read_inline_data(inode, page, iomap);
+ if (srcmap->type == IOMAP_INLINE)
+ iomap_read_inline_data(inode, page, srcmap);
else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
- status = __block_write_begin_int(page, pos, len, NULL, iomap);
+ status = __block_write_begin_int(page, pos, len, NULL, srcmap);
else
status = __iomap_write_begin(inode, pos, len, flags, page,
- iomap);
+ srcmap);
if (unlikely(status))
goto out_unlock;
@@ -740,16 +742,16 @@
}
static int
-iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
- unsigned copied, struct page *page, struct iomap *iomap)
+iomap_write_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied,
+ struct page *page, struct iomap *iomap, struct iomap *srcmap)
{
const struct iomap_page_ops *page_ops = iomap->page_ops;
loff_t old_size = inode->i_size;
int ret;
- if (iomap->type == IOMAP_INLINE) {
+ if (srcmap->type == IOMAP_INLINE) {
ret = iomap_write_end_inline(inode, page, iomap, pos, copied);
- } else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
+ } else if (srcmap->flags & IOMAP_F_BUFFER_HEAD) {
ret = block_write_end(NULL, inode->i_mapping, pos, len, copied,
page, NULL);
} else {
@@ -780,7 +782,7 @@
static loff_t
iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct iov_iter *i = data;
long status = 0;
@@ -814,7 +816,8 @@
break;
}
- status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
+ status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap,
+ srcmap);
if (unlikely(status))
break;
@@ -825,8 +828,8 @@
flush_dcache_page(page);
- status = iomap_write_end(inode, pos, bytes, copied, page,
- iomap);
+ status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
+ srcmap);
if (unlikely(status < 0))
break;
copied = status;
@@ -879,7 +882,7 @@
static loff_t
iomap_unshare_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
long status = 0;
ssize_t written = 0;
@@ -888,7 +891,7 @@
if (!(iomap->flags & IOMAP_F_SHARED))
return length;
/* don't bother with holes or unwritten extents */
- if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+ if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return length;
do {
@@ -897,11 +900,12 @@
struct page *page;
status = iomap_write_begin(inode, pos, bytes,
- IOMAP_WRITE_F_UNSHARE, &page, iomap);
+ IOMAP_WRITE_F_UNSHARE, &page, iomap, srcmap);
if (unlikely(status))
return status;
- status = iomap_write_end(inode, pos, bytes, bytes, page, iomap);
+ status = iomap_write_end(inode, pos, bytes, bytes, page, iomap,
+ srcmap);
if (unlikely(status <= 0)) {
if (WARN_ON_ONCE(status == 0))
return -EIO;
@@ -940,19 +944,19 @@
EXPORT_SYMBOL_GPL(iomap_file_unshare);
static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
- unsigned bytes, struct iomap *iomap)
+ unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
{
struct page *page;
int status;
- status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap);
+ status = iomap_write_begin(inode, pos, bytes, 0, &page, iomap, srcmap);
if (status)
return status;
zero_user(page, offset, bytes);
mark_page_accessed(page);
- return iomap_write_end(inode, pos, bytes, bytes, page, iomap);
+ return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
}
static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
@@ -964,14 +968,14 @@
static loff_t
iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
bool *did_zero = data;
loff_t written = 0;
int status;
/* already zeroed? we're done. */
- if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+ if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
return count;
do {
@@ -983,7 +987,8 @@
if (IS_DAX(inode))
status = iomap_dax_zero(pos, offset, bytes, iomap);
else
- status = iomap_zero(inode, pos, offset, bytes, iomap);
+ status = iomap_zero(inode, pos, offset, bytes, iomap,
+ srcmap);
if (status < 0)
return status;
@@ -1033,7 +1038,7 @@
static loff_t
iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
struct page *page = data;
int ret;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index da124ce..49bf978 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -358,7 +358,7 @@
static loff_t
iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
struct iomap_dio *dio = data;
diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
index f26fdd3..690ef2d 100644
--- a/fs/iomap/fiemap.c
+++ b/fs/iomap/fiemap.c
@@ -44,7 +44,7 @@
static loff_t
iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
- struct iomap *iomap)
+ struct iomap *iomap, struct iomap *srcmap)
{
struct fiemap_ctx *ctx = data;
loff_t ret = length;
@@ -111,7 +111,7 @@
static loff_t
iomap_bmap_actor(struct inode *inode, loff_t pos, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
sector_t *bno = data, addr;
diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
index c04bad4..89f61d9 100644
--- a/fs/iomap/seek.c
+++ b/fs/iomap/seek.c
@@ -119,7 +119,7 @@
static loff_t
iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
switch (iomap->type) {
case IOMAP_UNWRITTEN:
@@ -165,7 +165,7 @@
static loff_t
iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length,
- void *data, struct iomap *iomap)
+ void *data, struct iomap *iomap, struct iomap *srcmap)
{
switch (iomap->type) {
case IOMAP_HOLE:
diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
index 152a230..a648dbf 100644
--- a/fs/iomap/swapfile.c
+++ b/fs/iomap/swapfile.c
@@ -76,7 +76,8 @@
* distinction between written and unwritten extents.
*/
static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
- loff_t count, void *data, struct iomap *iomap)
+ loff_t count, void *data, struct iomap *iomap,
+ struct iomap *srcmap)
{
struct iomap_swapfile_info *isi = data;
int error;
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index f7b8b13..95719e1 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -928,7 +928,8 @@
loff_t offset,
loff_t length,
unsigned flags,
- struct iomap *iomap)
+ struct iomap *iomap,
+ struct iomap *srcmap)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
@@ -1161,7 +1162,8 @@
loff_t offset,
loff_t length,
unsigned flags,
- struct iomap *iomap)
+ struct iomap *iomap,
+ struct iomap *srcmap)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
@@ -1247,7 +1249,8 @@
loff_t offset,
loff_t length,
unsigned flags,
- struct iomap *iomap)
+ struct iomap *iomap,
+ struct iomap *srcmap)
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 53e6e22..8b09463 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -129,7 +129,8 @@
* The actual length is returned in iomap->length.
*/
int (*iomap_begin)(struct inode *inode, loff_t pos, loff_t length,
- unsigned flags, struct iomap *iomap);
+ unsigned flags, struct iomap *iomap,
+ struct iomap *srcmap);
/*
* Commit and/or unreserve space previous allocated using iomap_begin.
@@ -145,7 +146,7 @@
* Main iomap iterator function.
*/
typedef loff_t (*iomap_actor_t)(struct inode *inode, loff_t pos, loff_t len,
- void *data, struct iomap *iomap);
+ void *data, struct iomap *iomap, struct iomap *srcmap);
loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length,
unsigned flags, const struct iomap_ops *ops, void *data,
