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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_GFP_H
#define __LINUX_GFP_H
#include <linux/mmdebug.h>
#include <linux/mmzone.h>
#include <linux/stddef.h>
#include <linux/linkage.h>
#include <linux/topology.h>
struct vm_area_struct;
* In case of changes, please don't forget to update
* include/trace/events/mmflags.h and tools/perf/builtin-kmem.c
/* Plain integer GFP bitmasks. Do not use this directly. */
#define ___GFP_DMA 0x01u
#define ___GFP_HIGHMEM 0x02u
#define ___GFP_DMA32 0x04u
#define ___GFP_MOVABLE 0x08u
#define ___GFP_RECLAIMABLE 0x10u
#define ___GFP_HIGH 0x20u
#define ___GFP_IO 0x40u
#define ___GFP_FS 0x80u
#define ___GFP_WRITE 0x100u
#define ___GFP_NOWARN 0x200u
#define ___GFP_RETRY_MAYFAIL 0x400u
#define ___GFP_NOFAIL 0x800u
#define ___GFP_NORETRY 0x1000u
#define ___GFP_MEMALLOC 0x2000u
#define ___GFP_COMP 0x4000u
#define ___GFP_ZERO 0x8000u
#define ___GFP_NOMEMALLOC 0x10000u
#define ___GFP_HARDWALL 0x20000u
#define ___GFP_THISNODE 0x40000u
#define ___GFP_ATOMIC 0x80000u
#define ___GFP_ACCOUNT 0x100000u
#define ___GFP_DIRECT_RECLAIM 0x200000u
#define ___GFP_KSWAPD_RECLAIM 0x400000u
#define ___GFP_NOLOCKDEP 0x800000u
#define ___GFP_NOLOCKDEP 0
/* If the above are modified, __GFP_BITS_SHIFT may need updating */
* Physical address zone modifiers (see linux/mmzone.h - low four bits)
* Do not put any conditional on these. If necessary modify the definitions
* without the underscores and use them consistently. The definitions here may
* be used in bit comparisons.
#define __GFP_DMA ((__force gfp_t)___GFP_DMA)
#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM)
#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32)
#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */
* DOC: Page mobility and placement hints
* Page mobility and placement hints
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* These flags provide hints about how mobile the page is. Pages with similar
* mobility are placed within the same pageblocks to minimise problems due
* to external fragmentation.
* %__GFP_MOVABLE (also a zone modifier) indicates that the page can be
* moved by page migration during memory compaction or can be reclaimed.
* %__GFP_RECLAIMABLE is used for slab allocations that specify
* SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers.
* %__GFP_WRITE indicates the caller intends to dirty the page. Where possible,
* these pages will be spread between local zones to avoid all the dirty
* pages being in one zone (fair zone allocation policy).
* %__GFP_HARDWALL enforces the cpuset memory allocation policy.
* %__GFP_THISNODE forces the allocation to be satisified from the requested
* node with no fallbacks or placement policy enforcements.
* %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
#define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE)
#define __GFP_WRITE ((__force gfp_t)___GFP_WRITE)
#define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL)
#define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE)
#define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT)
* DOC: Watermark modifiers
* Watermark modifiers -- controls access to emergency reserves
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* %__GFP_HIGH indicates that the caller is high-priority and that granting
* the request is necessary before the system can make forward progress.
* For example, creating an IO context to clean pages.
* %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is
* high priority. Users are typically interrupt handlers. This may be
* used in conjunction with %__GFP_HIGH
* %__GFP_MEMALLOC allows access to all memory. This should only be used when
* the caller guarantees the allocation will allow more memory to be freed
* very shortly e.g. process exiting or swapping. Users either should
* be the MM or co-ordinating closely with the VM (e.g. swap over NFS).
* %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves.
* This takes precedence over the %__GFP_MEMALLOC flag if both are set.
#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC)
#define __GFP_HIGH ((__force gfp_t)___GFP_HIGH)
#define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)
#define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC)
* DOC: Reclaim modifiers
* Reclaim modifiers
* ~~~~~~~~~~~~~~~~~
* %__GFP_IO can start physical IO.
* %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the
* allocator recursing into the filesystem which might already be holding
* locks.
* %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim.
* This flag can be cleared to avoid unnecessary delays when a fallback
* option is available.
* %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when
* the low watermark is reached and have it reclaim pages until the high
* watermark is reached. A caller may wish to clear this flag when fallback
* options are available and the reclaim is likely to disrupt the system. The
* canonical example is THP allocation where a fallback is cheap but
* reclaim/compaction may cause indirect stalls.
* %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim.
* The default allocator behavior depends on the request size. We have a concept
* of so called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER).
* !costly allocations are too essential to fail so they are implicitly
* non-failing by default (with some exceptions like OOM victims might fail so
* the caller still has to check for failures) while costly requests try to be
* not disruptive and back off even without invoking the OOM killer.
* The following three modifiers might be used to override some of these
* implicit rules
* %__GFP_NORETRY: The VM implementation will try only very lightweight
* memory direct reclaim to get some memory under memory pressure (thus
* it can sleep). It will avoid disruptive actions like OOM killer. The
* caller must handle the failure which is quite likely to happen under
* heavy memory pressure. The flag is suitable when failure can easily be
* handled at small cost, such as reduced throughput
* %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim
* procedures that have previously failed if there is some indication
* that progress has been made else where. It can wait for other
* tasks to attempt high level approaches to freeing memory such as
* compaction (which removes fragmentation) and page-out.
* There is still a definite limit to the number of retries, but it is
* a larger limit than with %__GFP_NORETRY.
* Allocations with this flag may fail, but only when there is
* genuinely little unused memory. While these allocations do not
* directly trigger the OOM killer, their failure indicates that
* the system is likely to need to use the OOM killer soon. The
* caller must handle failure, but can reasonably do so by failing
* a higher-level request, or completing it only in a much less
* efficient manner.
* If the allocation does fail, and the caller is in a position to
* free some non-essential memory, doing so could benefit the system
* as a whole.
* %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
* cannot handle allocation failures. The allocation could block
* indefinitely but will never return with failure. Testing for
* failure is pointless.
* New users should be evaluated carefully (and the flag should be
* used only when there is no reasonable failure policy) but it is
* definitely preferable to use the flag rather than opencode endless
* loop around allocator.
* Using this flag for costly allocations is _highly_ discouraged.
#define __GFP_IO ((__force gfp_t)___GFP_IO)
#define __GFP_FS ((__force gfp_t)___GFP_FS)
#define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */
#define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */
#define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM))
#define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL)
#define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL)
#define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY)
* DOC: Action modifiers
* Action modifiers
* ~~~~~~~~~~~~~~~~
* %__GFP_NOWARN suppresses allocation failure reports.
* %__GFP_COMP address compound page metadata.
* %__GFP_ZERO returns a zeroed page on success.
#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
/* Disable lockdep for GFP context tracking */
#define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
/* Room for N __GFP_FOO bits */
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
* DOC: Useful GFP flag combinations
* Useful GFP flag combinations
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Useful GFP flag combinations that are commonly used. It is recommended
* that subsystems start with one of these combinations and then set/clear
* %__GFP_FOO flags as necessary.
* %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower
* watermark is applied to allow access to "atomic reserves"
* %GFP_KERNEL is typical for kernel-internal allocations. The caller requires
* %ZONE_NORMAL or a lower zone for direct access but can direct reclaim.
* %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is
* accounted to kmemcg.
* %GFP_NOWAIT is for kernel allocations that should not stall for direct
* reclaim, start physical IO or use any filesystem callback.
* %GFP_NOIO will use direct reclaim to discard clean pages or slab pages
* that do not require the starting of any physical IO.
* Please try to avoid using this flag directly and instead use
* memalloc_noio_{save,restore} to mark the whole scope which cannot
* perform any IO with a short explanation why. All allocation requests
* will inherit GFP_NOIO implicitly.
* %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces.
* Please try to avoid using this flag directly and instead use
* memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't
* recurse into the FS layer with a short explanation why. All allocation
* requests will inherit GFP_NOFS implicitly.
* %GFP_USER is for userspace allocations that also need to be directly
* accessibly by the kernel or hardware. It is typically used by hardware
* for buffers that are mapped to userspace (e.g. graphics) that hardware
* still must DMA to. cpuset limits are enforced for these allocations.
* %GFP_DMA exists for historical reasons and should be avoided where possible.
* The flags indicates that the caller requires that the lowest zone be
* used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but
* it would require careful auditing as some users really require it and
* others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the
* lowest zone as a type of emergency reserve.
* %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit
* address.
* %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,
* do not need to be directly accessible by the kernel but that cannot
* move once in use. An example may be a hardware allocation that maps
* data directly into userspace but has no addressing limitations.
* %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not
* need direct access to but can use kmap() when access is required. They
* are expected to be movable via page reclaim or page migration. Typically,
* pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE.
* %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They
* are compound allocations that will generally fail quickly if memory is not
* available and will not wake kswapd/kcompactd on failure. The _LIGHT
* version does not attempt reclaim/compaction at all and is by default used
* in page fault path, while the non-light is used by khugepaged.
#define GFP_DMA __GFP_DMA
#define GFP_DMA32 __GFP_DMA32
/* Convert GFP flags to their corresponding migrate type */
static inline int gfpflags_to_migratetype(const gfp_t gfp_flags)
if (unlikely(page_group_by_mobility_disabled))
/* Group based on mobility */
return (gfp_flags & GFP_MOVABLE_MASK) >> GFP_MOVABLE_SHIFT;
static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
return !!(gfp_flags & __GFP_DIRECT_RECLAIM);
* gfpflags_normal_context - is gfp_flags a normal sleepable context?
* @gfp_flags: gfp_flags to test
* Test whether @gfp_flags indicates that the allocation is from the
* %current context and allowed to sleep.
* An allocation being allowed to block doesn't mean it owns the %current
* context. When direct reclaim path tries to allocate memory, the
* allocation context is nested inside whatever %current was doing at the
* time of the original allocation. The nested allocation may be allowed
* to block but modifying anything %current owns can corrupt the outer
* context's expectations.
* %true result from this function indicates that the allocation context
* can sleep and use anything that's associated with %current.
static inline bool gfpflags_normal_context(const gfp_t gfp_flags)
return (gfp_flags & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC)) ==
* GFP_ZONE_TABLE is a word size bitstring that is used for looking up the
* zone to use given the lowest 4 bits of gfp_t. Entries are GFP_ZONES_SHIFT
* bits long and there are 16 of them to cover all possible combinations of
* The zone fallback order is MOVABLE=>HIGHMEM=>NORMAL=>DMA32=>DMA.
* But GFP_MOVABLE is not only a zone specifier but also an allocation
* policy. Therefore __GFP_MOVABLE plus another zone selector is valid.
* Only 1 bit of the lowest 3 bits (DMA,DMA32,HIGHMEM) can be set to "1".
* bit result
* =================
* 0x0 => NORMAL
* 0x1 => DMA or NORMAL
* 0x2 => HIGHMEM or NORMAL
* 0x3 => BAD (DMA+HIGHMEM)
* 0x4 => DMA32 or NORMAL
* 0x5 => BAD (DMA+DMA32)
* 0x6 => BAD (HIGHMEM+DMA32)
* 0x7 => BAD (HIGHMEM+DMA32+DMA)
* 0x8 => NORMAL (MOVABLE+0)
* 0xa => MOVABLE (Movable is valid only if HIGHMEM is set too)
* 0xc => DMA32 or NORMAL (MOVABLE+DMA32)
* 0xd => BAD (MOVABLE+DMA32+DMA)
* GFP_ZONES_SHIFT must be <= 2 on 32 bit platforms.
#if defined(CONFIG_ZONE_DEVICE) && (MAX_NR_ZONES-1) <= 4
/* ZONE_DEVICE is not a valid GFP zone specifier */
#error GFP_ZONES_SHIFT too large to create GFP_ZONE_TABLE integer
#define GFP_ZONE_TABLE ( \
* GFP_ZONE_BAD is a bitmap for all combinations of __GFP_DMA, __GFP_DMA32
* __GFP_HIGHMEM and __GFP_MOVABLE that are not permitted. One flag per
* entry starting with bit 0. Bit is set if the combination is not
* allowed.
#define GFP_ZONE_BAD ( \
1 << (___GFP_DMA | ___GFP_HIGHMEM) \
| 1 << (___GFP_DMA | ___GFP_DMA32) \
| 1 << (___GFP_DMA32 | ___GFP_HIGHMEM) \
| 1 << (___GFP_DMA | ___GFP_DMA32 | ___GFP_HIGHMEM) \
| 1 << (___GFP_MOVABLE | ___GFP_HIGHMEM | ___GFP_DMA) \
| 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA) \
| 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_HIGHMEM) \
| 1 << (___GFP_MOVABLE | ___GFP_DMA32 | ___GFP_DMA | ___GFP_HIGHMEM) \
static inline enum zone_type gfp_zone(gfp_t flags)
enum zone_type z;
int bit = (__force int) (flags & GFP_ZONEMASK);
((1 << GFP_ZONES_SHIFT) - 1);
VM_BUG_ON((GFP_ZONE_BAD >> bit) & 1);
return z;
* There is only one page-allocator function, and two main namespaces to
* it. The alloc_page*() variants return 'struct page *' and as such
* can allocate highmem pages, the *get*page*() variants return
* virtual kernel addresses to the allocated page(s).
static inline int gfp_zonelist(gfp_t flags)
if (unlikely(flags & __GFP_THISNODE))
* We get the zone list from the current node and the gfp_mask.
* This zone list contains a maximum of MAXNODES*MAX_NR_ZONES zones.
* There are two zonelists per node, one for all zones with memory and
* one containing just zones from the node the zonelist belongs to.
* For the normal case of non-DISCONTIGMEM systems the NODE_DATA() gets
* optimized to &contig_page_data at compile-time.
static inline struct zonelist *node_zonelist(int nid, gfp_t flags)
return NODE_DATA(nid)->node_zonelists + gfp_zonelist(flags);
static inline void arch_free_page(struct page *page, int order) { }
static inline void arch_alloc_page(struct page *page, int order) { }
struct page *
__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
nodemask_t *nodemask);
static inline struct page *
__alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
return __alloc_pages_nodemask(gfp_mask, order, preferred_nid, NULL);
* Allocate pages, preferring the node given as nid. The node must be valid and
* online. For more general interface, see alloc_pages_node().
static inline struct page *
__alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));
return __alloc_pages(gfp_mask, order, nid);
* Allocate pages, preferring the node given as nid. When nid == NUMA_NO_NODE,
* prefer the current CPU's closest node. Otherwise node must be valid and
* online.
static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
unsigned int order)
if (nid == NUMA_NO_NODE)
nid = numa_mem_id();
return __alloc_pages_node(nid, gfp_mask, order);
extern struct page *alloc_pages_current(gfp_t gfp_mask, unsigned order);
static inline struct page *
alloc_pages(gfp_t gfp_mask, unsigned int order)
return alloc_pages_current(gfp_mask, order);
extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
struct vm_area_struct *vma, unsigned long addr,
int node, bool hugepage);
#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
alloc_pages_vma(gfp_mask, order, vma, addr, numa_node_id(), true)
#define alloc_pages(gfp_mask, order) \
alloc_pages_node(numa_node_id(), gfp_mask, order)
#define alloc_pages_vma(gfp_mask, order, vma, addr, node, false)\
alloc_pages(gfp_mask, order)
#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
alloc_pages(gfp_mask, order)
#define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
#define alloc_page_vma(gfp_mask, vma, addr) \
alloc_pages_vma(gfp_mask, 0, vma, addr, numa_node_id(), false)
#define alloc_page_vma_node(gfp_mask, vma, addr, node) \
alloc_pages_vma(gfp_mask, 0, vma, addr, node, false)
extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
extern unsigned long get_zeroed_page(gfp_t gfp_mask);
void *alloc_pages_exact(size_t size, gfp_t gfp_mask);
void free_pages_exact(void *virt, size_t size);
void * __meminit alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask);
#define __get_free_page(gfp_mask) \
__get_free_pages((gfp_mask), 0)
#define __get_dma_pages(gfp_mask, order) \
__get_free_pages((gfp_mask) | GFP_DMA, (order))
extern void __free_pages(struct page *page, unsigned int order);
extern void free_pages(unsigned long addr, unsigned int order);
extern void free_unref_page(struct page *page);
extern void free_unref_page_list(struct list_head *list);
struct page_frag_cache;
extern void __page_frag_cache_drain(struct page *page, unsigned int count);
extern void *page_frag_alloc(struct page_frag_cache *nc,
unsigned int fragsz, gfp_t gfp_mask);
extern void page_frag_free(void *addr);
#define __free_page(page) __free_pages((page), 0)
#define free_page(addr) free_pages((addr), 0)
void page_alloc_init(void);
void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp);
void drain_all_pages(struct zone *zone);
void drain_local_pages(struct zone *zone);
void page_alloc_init_late(void);
* gfp_allowed_mask is set to GFP_BOOT_MASK during early boot to restrict what
* GFP flags are used before interrupts are enabled. Once interrupts are
* enabled, it is set to __GFP_BITS_MASK while the system is running. During
* hibernation, it is used by PM to avoid I/O during memory allocation while
* devices are suspended.
extern gfp_t gfp_allowed_mask;
/* Returns true if the gfp_mask allows use of ALLOC_NO_WATERMARK */
bool gfp_pfmemalloc_allowed(gfp_t gfp_mask);
extern void pm_restrict_gfp_mask(void);
extern void pm_restore_gfp_mask(void);
extern bool pm_suspended_storage(void);
static inline bool pm_suspended_storage(void)
return false;
#endif /* CONFIG_PM_SLEEP */
/* The below functions must be run on a range from a single zone. */
extern int alloc_contig_range(unsigned long start, unsigned long end,
unsigned migratetype, gfp_t gfp_mask);
extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
/* CMA stuff */
extern void init_cma_reserved_pageblock(struct page *page);
#endif /* __LINUX_GFP_H */