1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_GFP_TYPES_H
3 #define __LINUX_GFP_TYPES_H
5 #include <linux/bits.h>
7 /* The typedef is in types.h but we want the documentation here */
10 * typedef gfp_t - Memory allocation flags.
12 * GFP flags are commonly used throughout Linux to indicate how memory
13 * should be allocated. The GFP acronym stands for get_free_pages(),
14 * the underlying memory allocation function. Not every GFP flag is
15 * supported by every function which may allocate memory. Most users
16 * will want to use a plain ``GFP_KERNEL``.
18 typedef unsigned int __bitwise gfp_t;
22 * In case of changes, please don't forget to update
23 * include/trace/events/mmflags.h and tools/perf/builtin-kmem.c
31 ___GFP_RECLAIMABLE_BIT,
36 ___GFP_UNUSED_BIT, /* 0x200u unused */
37 ___GFP_DIRECT_RECLAIM_BIT,
38 ___GFP_KSWAPD_RECLAIM_BIT,
41 ___GFP_RETRY_MAYFAIL_BIT,
46 ___GFP_NOMEMALLOC_BIT,
51 #ifdef CONFIG_KASAN_HW_TAGS
53 ___GFP_SKIP_KASAN_BIT,
58 #ifdef CONFIG_SLAB_OBJ_EXT
59 ___GFP_NO_OBJ_EXT_BIT,
64 /* Plain integer GFP bitmasks. Do not use this directly. */
65 #define ___GFP_DMA BIT(___GFP_DMA_BIT)
66 #define ___GFP_HIGHMEM BIT(___GFP_HIGHMEM_BIT)
67 #define ___GFP_DMA32 BIT(___GFP_DMA32_BIT)
68 #define ___GFP_MOVABLE BIT(___GFP_MOVABLE_BIT)
69 #define ___GFP_RECLAIMABLE BIT(___GFP_RECLAIMABLE_BIT)
70 #define ___GFP_HIGH BIT(___GFP_HIGH_BIT)
71 #define ___GFP_IO BIT(___GFP_IO_BIT)
72 #define ___GFP_FS BIT(___GFP_FS_BIT)
73 #define ___GFP_ZERO BIT(___GFP_ZERO_BIT)
75 #define ___GFP_DIRECT_RECLAIM BIT(___GFP_DIRECT_RECLAIM_BIT)
76 #define ___GFP_KSWAPD_RECLAIM BIT(___GFP_KSWAPD_RECLAIM_BIT)
77 #define ___GFP_WRITE BIT(___GFP_WRITE_BIT)
78 #define ___GFP_NOWARN BIT(___GFP_NOWARN_BIT)
79 #define ___GFP_RETRY_MAYFAIL BIT(___GFP_RETRY_MAYFAIL_BIT)
80 #define ___GFP_NOFAIL BIT(___GFP_NOFAIL_BIT)
81 #define ___GFP_NORETRY BIT(___GFP_NORETRY_BIT)
82 #define ___GFP_MEMALLOC BIT(___GFP_MEMALLOC_BIT)
83 #define ___GFP_COMP BIT(___GFP_COMP_BIT)
84 #define ___GFP_NOMEMALLOC BIT(___GFP_NOMEMALLOC_BIT)
85 #define ___GFP_HARDWALL BIT(___GFP_HARDWALL_BIT)
86 #define ___GFP_THISNODE BIT(___GFP_THISNODE_BIT)
87 #define ___GFP_ACCOUNT BIT(___GFP_ACCOUNT_BIT)
88 #define ___GFP_ZEROTAGS BIT(___GFP_ZEROTAGS_BIT)
89 #ifdef CONFIG_KASAN_HW_TAGS
90 #define ___GFP_SKIP_ZERO BIT(___GFP_SKIP_ZERO_BIT)
91 #define ___GFP_SKIP_KASAN BIT(___GFP_SKIP_KASAN_BIT)
93 #define ___GFP_SKIP_ZERO 0
94 #define ___GFP_SKIP_KASAN 0
97 #define ___GFP_NOLOCKDEP BIT(___GFP_NOLOCKDEP_BIT)
99 #define ___GFP_NOLOCKDEP 0
101 #ifdef CONFIG_SLAB_OBJ_EXT
102 #define ___GFP_NO_OBJ_EXT BIT(___GFP_NO_OBJ_EXT_BIT)
104 #define ___GFP_NO_OBJ_EXT 0
108 * Physical address zone modifiers (see linux/mmzone.h - low four bits)
110 * Do not put any conditional on these. If necessary modify the definitions
111 * without the underscores and use them consistently. The definitions here may
112 * be used in bit comparisons.
114 #define __GFP_DMA ((__force gfp_t)___GFP_DMA)
115 #define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM)
116 #define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32)
117 #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */
118 #define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE)
121 * DOC: Page mobility and placement hints
123 * Page mobility and placement hints
124 * ---------------------------------
126 * These flags provide hints about how mobile the page is. Pages with similar
127 * mobility are placed within the same pageblocks to minimise problems due
128 * to external fragmentation.
130 * %__GFP_MOVABLE (also a zone modifier) indicates that the page can be
131 * moved by page migration during memory compaction or can be reclaimed.
133 * %__GFP_RECLAIMABLE is used for slab allocations that specify
134 * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers.
136 * %__GFP_WRITE indicates the caller intends to dirty the page. Where possible,
137 * these pages will be spread between local zones to avoid all the dirty
138 * pages being in one zone (fair zone allocation policy).
140 * %__GFP_HARDWALL enforces the cpuset memory allocation policy.
142 * %__GFP_THISNODE forces the allocation to be satisfied from the requested
143 * node with no fallbacks or placement policy enforcements.
145 * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
147 * %__GFP_NO_OBJ_EXT causes slab allocation to have no object extension.
149 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE)
150 #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE)
151 #define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL)
152 #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE)
153 #define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT)
154 #define __GFP_NO_OBJ_EXT ((__force gfp_t)___GFP_NO_OBJ_EXT)
157 * DOC: Watermark modifiers
159 * Watermark modifiers -- controls access to emergency reserves
160 * ------------------------------------------------------------
162 * %__GFP_HIGH indicates that the caller is high-priority and that granting
163 * the request is necessary before the system can make forward progress.
164 * For example creating an IO context to clean pages and requests
165 * from atomic context.
167 * %__GFP_MEMALLOC allows access to all memory. This should only be used when
168 * the caller guarantees the allocation will allow more memory to be freed
169 * very shortly e.g. process exiting or swapping. Users either should
170 * be the MM or co-ordinating closely with the VM (e.g. swap over NFS).
171 * Users of this flag have to be extremely careful to not deplete the reserve
172 * completely and implement a throttling mechanism which controls the
173 * consumption of the reserve based on the amount of freed memory.
174 * Usage of a pre-allocated pool (e.g. mempool) should be always considered
175 * before using this flag.
177 * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves.
178 * This takes precedence over the %__GFP_MEMALLOC flag if both are set.
180 #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH)
181 #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)
182 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC)
185 * DOC: Reclaim modifiers
189 * Please note that all the following flags are only applicable to sleepable
190 * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them).
192 * %__GFP_IO can start physical IO.
194 * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the
195 * allocator recursing into the filesystem which might already be holding
198 * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim.
199 * This flag can be cleared to avoid unnecessary delays when a fallback
200 * option is available.
202 * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when
203 * the low watermark is reached and have it reclaim pages until the high
204 * watermark is reached. A caller may wish to clear this flag when fallback
205 * options are available and the reclaim is likely to disrupt the system. The
206 * canonical example is THP allocation where a fallback is cheap but
207 * reclaim/compaction may cause indirect stalls.
209 * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim.
211 * The default allocator behavior depends on the request size. We have a concept
212 * of so-called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER).
213 * !costly allocations are too essential to fail so they are implicitly
214 * non-failing by default (with some exceptions like OOM victims might fail so
215 * the caller still has to check for failures) while costly requests try to be
216 * not disruptive and back off even without invoking the OOM killer.
217 * The following three modifiers might be used to override some of these
220 * %__GFP_NORETRY: The VM implementation will try only very lightweight
221 * memory direct reclaim to get some memory under memory pressure (thus
222 * it can sleep). It will avoid disruptive actions like OOM killer. The
223 * caller must handle the failure which is quite likely to happen under
224 * heavy memory pressure. The flag is suitable when failure can easily be
225 * handled at small cost, such as reduced throughput.
227 * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim
228 * procedures that have previously failed if there is some indication
229 * that progress has been made elsewhere. It can wait for other
230 * tasks to attempt high-level approaches to freeing memory such as
231 * compaction (which removes fragmentation) and page-out.
232 * There is still a definite limit to the number of retries, but it is
233 * a larger limit than with %__GFP_NORETRY.
234 * Allocations with this flag may fail, but only when there is
235 * genuinely little unused memory. While these allocations do not
236 * directly trigger the OOM killer, their failure indicates that
237 * the system is likely to need to use the OOM killer soon. The
238 * caller must handle failure, but can reasonably do so by failing
239 * a higher-level request, or completing it only in a much less
241 * If the allocation does fail, and the caller is in a position to
242 * free some non-essential memory, doing so could benefit the system
245 * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
246 * cannot handle allocation failures. The allocation could block
247 * indefinitely but will never return with failure. Testing for
248 * failure is pointless.
249 * New users should be evaluated carefully (and the flag should be
250 * used only when there is no reasonable failure policy) but it is
251 * definitely preferable to use the flag rather than opencode endless
252 * loop around allocator.
253 * Using this flag for costly allocations is _highly_ discouraged.
255 #define __GFP_IO ((__force gfp_t)___GFP_IO)
256 #define __GFP_FS ((__force gfp_t)___GFP_FS)
257 #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */
258 #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */
259 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM))
260 #define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL)
261 #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL)
262 #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY)
265 * DOC: Action modifiers
270 * %__GFP_NOWARN suppresses allocation failure reports.
272 * %__GFP_COMP address compound page metadata.
274 * %__GFP_ZERO returns a zeroed page on success.
276 * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself
277 * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that
278 * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting
279 * memory tags at the same time as zeroing memory has minimal additional
280 * performance impact.
282 * %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation.
283 * Used for userspace and vmalloc pages; the latter are unpoisoned by
284 * kasan_unpoison_vmalloc instead. For userspace pages, results in
285 * poisoning being skipped as well, see should_skip_kasan_poison for
286 * details. Only effective in HW_TAGS mode.
288 #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
289 #define __GFP_COMP ((__force gfp_t)___GFP_COMP)
290 #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
291 #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS)
292 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO)
293 #define __GFP_SKIP_KASAN ((__force gfp_t)___GFP_SKIP_KASAN)
295 /* Disable lockdep for GFP context tracking */
296 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
298 /* Room for N __GFP_FOO bits */
299 #define __GFP_BITS_SHIFT ___GFP_LAST_BIT
300 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
303 * DOC: Useful GFP flag combinations
305 * Useful GFP flag combinations
306 * ----------------------------
308 * Useful GFP flag combinations that are commonly used. It is recommended
309 * that subsystems start with one of these combinations and then set/clear
310 * %__GFP_FOO flags as necessary.
312 * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower
313 * watermark is applied to allow access to "atomic reserves".
314 * The current implementation doesn't support NMI and few other strict
315 * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT.
317 * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires
318 * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim.
320 * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is
321 * accounted to kmemcg.
323 * %GFP_NOWAIT is for kernel allocations that should not stall for direct
324 * reclaim, start physical IO or use any filesystem callback. It is very
325 * likely to fail to allocate memory, even for very small allocations.
327 * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages
328 * that do not require the starting of any physical IO.
329 * Please try to avoid using this flag directly and instead use
330 * memalloc_noio_{save,restore} to mark the whole scope which cannot
331 * perform any IO with a short explanation why. All allocation requests
332 * will inherit GFP_NOIO implicitly.
334 * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces.
335 * Please try to avoid using this flag directly and instead use
336 * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't
337 * recurse into the FS layer with a short explanation why. All allocation
338 * requests will inherit GFP_NOFS implicitly.
340 * %GFP_USER is for userspace allocations that also need to be directly
341 * accessibly by the kernel or hardware. It is typically used by hardware
342 * for buffers that are mapped to userspace (e.g. graphics) that hardware
343 * still must DMA to. cpuset limits are enforced for these allocations.
345 * %GFP_DMA exists for historical reasons and should be avoided where possible.
346 * The flags indicates that the caller requires that the lowest zone be
347 * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but
348 * it would require careful auditing as some users really require it and
349 * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the
350 * lowest zone as a type of emergency reserve.
352 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit
353 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory
354 * because the DMA32 kmalloc cache array is not implemented.
355 * (Reason: there is no such user in kernel).
357 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,
358 * do not need to be directly accessible by the kernel but that cannot
359 * move once in use. An example may be a hardware allocation that maps
360 * data directly into userspace but has no addressing limitations.
362 * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not
363 * need direct access to but can use kmap() when access is required. They
364 * are expected to be movable via page reclaim or page migration. Typically,
365 * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE.
367 * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They
368 * are compound allocations that will generally fail quickly if memory is not
369 * available and will not wake kswapd/kcompactd on failure. The _LIGHT
370 * version does not attempt reclaim/compaction at all and is by default used
371 * in page fault path, while the non-light is used by khugepaged.
373 #define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM)
374 #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS)
375 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)
376 #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM | __GFP_NOWARN)
377 #define GFP_NOIO (__GFP_RECLAIM)
378 #define GFP_NOFS (__GFP_RECLAIM | __GFP_IO)
379 #define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
380 #define GFP_DMA __GFP_DMA
381 #define GFP_DMA32 __GFP_DMA32
382 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM)
383 #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | __GFP_SKIP_KASAN)
384 #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \
385 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM)
386 #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM)
388 #endif /* __LINUX_GFP_TYPES_H */