1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_GFP_TYPES_H
3 #define __LINUX_GFP_TYPES_H
4 
5 /* The typedef is in types.h but we want the documentation here */
6 #if 0
7 /**
8  * typedef gfp_t - Memory allocation flags.
9  *
10  * GFP flags are commonly used throughout Linux to indicate how memory
11  * should be allocated.  The GFP acronym stands for get_free_pages(),
12  * the underlying memory allocation function.  Not every GFP flag is
13  * supported by every function which may allocate memory.  Most users
14  * will want to use a plain ``GFP_KERNEL``.
15  */
16 typedef unsigned int __bitwise gfp_t;
17 #endif
18 
19 /*
20  * In case of changes, please don't forget to update
21  * include/trace/events/mmflags.h and tools/perf/builtin-kmem.c
22  */
23 
24 /* Plain integer GFP bitmasks. Do not use this directly. */
25 #define ___GFP_DMA		0x01u
26 #define ___GFP_HIGHMEM		0x02u
27 #define ___GFP_DMA32		0x04u
28 #define ___GFP_MOVABLE		0x08u
29 #define ___GFP_RECLAIMABLE	0x10u
30 #define ___GFP_HIGH		0x20u
31 #define ___GFP_IO		0x40u
32 #define ___GFP_FS		0x80u
33 #define ___GFP_ZERO		0x100u
34 #define ___GFP_ATOMIC		0x200u
35 #define ___GFP_DIRECT_RECLAIM	0x400u
36 #define ___GFP_KSWAPD_RECLAIM	0x800u
37 #define ___GFP_WRITE		0x1000u
38 #define ___GFP_NOWARN		0x2000u
39 #define ___GFP_RETRY_MAYFAIL	0x4000u
40 #define ___GFP_NOFAIL		0x8000u
41 #define ___GFP_NORETRY		0x10000u
42 #define ___GFP_MEMALLOC		0x20000u
43 #define ___GFP_COMP		0x40000u
44 #define ___GFP_NOMEMALLOC	0x80000u
45 #define ___GFP_HARDWALL		0x100000u
46 #define ___GFP_THISNODE		0x200000u
47 #define ___GFP_ACCOUNT		0x400000u
48 #define ___GFP_ZEROTAGS		0x800000u
49 #ifdef CONFIG_KASAN_HW_TAGS
50 #define ___GFP_SKIP_ZERO		0x1000000u
51 #define ___GFP_SKIP_KASAN_UNPOISON	0x2000000u
52 #define ___GFP_SKIP_KASAN_POISON	0x4000000u
53 #else
54 #define ___GFP_SKIP_ZERO		0
55 #define ___GFP_SKIP_KASAN_UNPOISON	0
56 #define ___GFP_SKIP_KASAN_POISON	0
57 #endif
58 #ifdef CONFIG_LOCKDEP
59 #define ___GFP_NOLOCKDEP	0x8000000u
60 #else
61 #define ___GFP_NOLOCKDEP	0
62 #endif
63 /* If the above are modified, __GFP_BITS_SHIFT may need updating */
64 
65 /*
66  * Physical address zone modifiers (see linux/mmzone.h - low four bits)
67  *
68  * Do not put any conditional on these. If necessary modify the definitions
69  * without the underscores and use them consistently. The definitions here may
70  * be used in bit comparisons.
71  */
72 #define __GFP_DMA	((__force gfp_t)___GFP_DMA)
73 #define __GFP_HIGHMEM	((__force gfp_t)___GFP_HIGHMEM)
74 #define __GFP_DMA32	((__force gfp_t)___GFP_DMA32)
75 #define __GFP_MOVABLE	((__force gfp_t)___GFP_MOVABLE)  /* ZONE_MOVABLE allowed */
76 #define GFP_ZONEMASK	(__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE)
77 
78 /**
79  * DOC: Page mobility and placement hints
80  *
81  * Page mobility and placement hints
82  * ---------------------------------
83  *
84  * These flags provide hints about how mobile the page is. Pages with similar
85  * mobility are placed within the same pageblocks to minimise problems due
86  * to external fragmentation.
87  *
88  * %__GFP_MOVABLE (also a zone modifier) indicates that the page can be
89  * moved by page migration during memory compaction or can be reclaimed.
90  *
91  * %__GFP_RECLAIMABLE is used for slab allocations that specify
92  * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers.
93  *
94  * %__GFP_WRITE indicates the caller intends to dirty the page. Where possible,
95  * these pages will be spread between local zones to avoid all the dirty
96  * pages being in one zone (fair zone allocation policy).
97  *
98  * %__GFP_HARDWALL enforces the cpuset memory allocation policy.
99  *
100  * %__GFP_THISNODE forces the allocation to be satisfied from the requested
101  * node with no fallbacks or placement policy enforcements.
102  *
103  * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
104  */
105 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE)
106 #define __GFP_WRITE	((__force gfp_t)___GFP_WRITE)
107 #define __GFP_HARDWALL   ((__force gfp_t)___GFP_HARDWALL)
108 #define __GFP_THISNODE	((__force gfp_t)___GFP_THISNODE)
109 #define __GFP_ACCOUNT	((__force gfp_t)___GFP_ACCOUNT)
110 
111 /**
112  * DOC: Watermark modifiers
113  *
114  * Watermark modifiers -- controls access to emergency reserves
115  * ------------------------------------------------------------
116  *
117  * %__GFP_HIGH indicates that the caller is high-priority and that granting
118  * the request is necessary before the system can make forward progress.
119  * For example, creating an IO context to clean pages.
120  *
121  * %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is
122  * high priority. Users are typically interrupt handlers. This may be
123  * used in conjunction with %__GFP_HIGH
124  *
125  * %__GFP_MEMALLOC allows access to all memory. This should only be used when
126  * the caller guarantees the allocation will allow more memory to be freed
127  * very shortly e.g. process exiting or swapping. Users either should
128  * be the MM or co-ordinating closely with the VM (e.g. swap over NFS).
129  * Users of this flag have to be extremely careful to not deplete the reserve
130  * completely and implement a throttling mechanism which controls the
131  * consumption of the reserve based on the amount of freed memory.
132  * Usage of a pre-allocated pool (e.g. mempool) should be always considered
133  * before using this flag.
134  *
135  * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves.
136  * This takes precedence over the %__GFP_MEMALLOC flag if both are set.
137  */
138 #define __GFP_ATOMIC	((__force gfp_t)___GFP_ATOMIC)
139 #define __GFP_HIGH	((__force gfp_t)___GFP_HIGH)
140 #define __GFP_MEMALLOC	((__force gfp_t)___GFP_MEMALLOC)
141 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC)
142 
143 /**
144  * DOC: Reclaim modifiers
145  *
146  * Reclaim modifiers
147  * -----------------
148  * Please note that all the following flags are only applicable to sleepable
149  * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them).
150  *
151  * %__GFP_IO can start physical IO.
152  *
153  * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the
154  * allocator recursing into the filesystem which might already be holding
155  * locks.
156  *
157  * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim.
158  * This flag can be cleared to avoid unnecessary delays when a fallback
159  * option is available.
160  *
161  * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when
162  * the low watermark is reached and have it reclaim pages until the high
163  * watermark is reached. A caller may wish to clear this flag when fallback
164  * options are available and the reclaim is likely to disrupt the system. The
165  * canonical example is THP allocation where a fallback is cheap but
166  * reclaim/compaction may cause indirect stalls.
167  *
168  * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim.
169  *
170  * The default allocator behavior depends on the request size. We have a concept
171  * of so called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER).
172  * !costly allocations are too essential to fail so they are implicitly
173  * non-failing by default (with some exceptions like OOM victims might fail so
174  * the caller still has to check for failures) while costly requests try to be
175  * not disruptive and back off even without invoking the OOM killer.
176  * The following three modifiers might be used to override some of these
177  * implicit rules
178  *
179  * %__GFP_NORETRY: The VM implementation will try only very lightweight
180  * memory direct reclaim to get some memory under memory pressure (thus
181  * it can sleep). It will avoid disruptive actions like OOM killer. The
182  * caller must handle the failure which is quite likely to happen under
183  * heavy memory pressure. The flag is suitable when failure can easily be
184  * handled at small cost, such as reduced throughput
185  *
186  * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim
187  * procedures that have previously failed if there is some indication
188  * that progress has been made else where.  It can wait for other
189  * tasks to attempt high level approaches to freeing memory such as
190  * compaction (which removes fragmentation) and page-out.
191  * There is still a definite limit to the number of retries, but it is
192  * a larger limit than with %__GFP_NORETRY.
193  * Allocations with this flag may fail, but only when there is
194  * genuinely little unused memory. While these allocations do not
195  * directly trigger the OOM killer, their failure indicates that
196  * the system is likely to need to use the OOM killer soon.  The
197  * caller must handle failure, but can reasonably do so by failing
198  * a higher-level request, or completing it only in a much less
199  * efficient manner.
200  * If the allocation does fail, and the caller is in a position to
201  * free some non-essential memory, doing so could benefit the system
202  * as a whole.
203  *
204  * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
205  * cannot handle allocation failures. The allocation could block
206  * indefinitely but will never return with failure. Testing for
207  * failure is pointless.
208  * New users should be evaluated carefully (and the flag should be
209  * used only when there is no reasonable failure policy) but it is
210  * definitely preferable to use the flag rather than opencode endless
211  * loop around allocator.
212  * Using this flag for costly allocations is _highly_ discouraged.
213  */
214 #define __GFP_IO	((__force gfp_t)___GFP_IO)
215 #define __GFP_FS	((__force gfp_t)___GFP_FS)
216 #define __GFP_DIRECT_RECLAIM	((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */
217 #define __GFP_KSWAPD_RECLAIM	((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */
218 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM))
219 #define __GFP_RETRY_MAYFAIL	((__force gfp_t)___GFP_RETRY_MAYFAIL)
220 #define __GFP_NOFAIL	((__force gfp_t)___GFP_NOFAIL)
221 #define __GFP_NORETRY	((__force gfp_t)___GFP_NORETRY)
222 
223 /**
224  * DOC: Action modifiers
225  *
226  * Action modifiers
227  * ----------------
228  *
229  * %__GFP_NOWARN suppresses allocation failure reports.
230  *
231  * %__GFP_COMP address compound page metadata.
232  *
233  * %__GFP_ZERO returns a zeroed page on success.
234  *
235  * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself
236  * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that
237  * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting
238  * memory tags at the same time as zeroing memory has minimal additional
239  * performace impact.
240  *
241  * %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation.
242  * Only effective in HW_TAGS mode.
243  *
244  * %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation.
245  * Typically, used for userspace pages. Only effective in HW_TAGS mode.
246  */
247 #define __GFP_NOWARN	((__force gfp_t)___GFP_NOWARN)
248 #define __GFP_COMP	((__force gfp_t)___GFP_COMP)
249 #define __GFP_ZERO	((__force gfp_t)___GFP_ZERO)
250 #define __GFP_ZEROTAGS	((__force gfp_t)___GFP_ZEROTAGS)
251 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO)
252 #define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON)
253 #define __GFP_SKIP_KASAN_POISON   ((__force gfp_t)___GFP_SKIP_KASAN_POISON)
254 
255 /* Disable lockdep for GFP context tracking */
256 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
257 
258 /* Room for N __GFP_FOO bits */
259 #define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP))
260 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
261 
262 /**
263  * DOC: Useful GFP flag combinations
264  *
265  * Useful GFP flag combinations
266  * ----------------------------
267  *
268  * Useful GFP flag combinations that are commonly used. It is recommended
269  * that subsystems start with one of these combinations and then set/clear
270  * %__GFP_FOO flags as necessary.
271  *
272  * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower
273  * watermark is applied to allow access to "atomic reserves".
274  * The current implementation doesn't support NMI and few other strict
275  * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT.
276  *
277  * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires
278  * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim.
279  *
280  * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is
281  * accounted to kmemcg.
282  *
283  * %GFP_NOWAIT is for kernel allocations that should not stall for direct
284  * reclaim, start physical IO or use any filesystem callback.
285  *
286  * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages
287  * that do not require the starting of any physical IO.
288  * Please try to avoid using this flag directly and instead use
289  * memalloc_noio_{save,restore} to mark the whole scope which cannot
290  * perform any IO with a short explanation why. All allocation requests
291  * will inherit GFP_NOIO implicitly.
292  *
293  * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces.
294  * Please try to avoid using this flag directly and instead use
295  * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't
296  * recurse into the FS layer with a short explanation why. All allocation
297  * requests will inherit GFP_NOFS implicitly.
298  *
299  * %GFP_USER is for userspace allocations that also need to be directly
300  * accessibly by the kernel or hardware. It is typically used by hardware
301  * for buffers that are mapped to userspace (e.g. graphics) that hardware
302  * still must DMA to. cpuset limits are enforced for these allocations.
303  *
304  * %GFP_DMA exists for historical reasons and should be avoided where possible.
305  * The flags indicates that the caller requires that the lowest zone be
306  * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but
307  * it would require careful auditing as some users really require it and
308  * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the
309  * lowest zone as a type of emergency reserve.
310  *
311  * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit
312  * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory
313  * because the DMA32 kmalloc cache array is not implemented.
314  * (Reason: there is no such user in kernel).
315  *
316  * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,
317  * do not need to be directly accessible by the kernel but that cannot
318  * move once in use. An example may be a hardware allocation that maps
319  * data directly into userspace but has no addressing limitations.
320  *
321  * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not
322  * need direct access to but can use kmap() when access is required. They
323  * are expected to be movable via page reclaim or page migration. Typically,
324  * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE.
325  *
326  * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They
327  * are compound allocations that will generally fail quickly if memory is not
328  * available and will not wake kswapd/kcompactd on failure. The _LIGHT
329  * version does not attempt reclaim/compaction at all and is by default used
330  * in page fault path, while the non-light is used by khugepaged.
331  */
332 #define GFP_ATOMIC	(__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM)
333 #define GFP_KERNEL	(__GFP_RECLAIM | __GFP_IO | __GFP_FS)
334 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)
335 #define GFP_NOWAIT	(__GFP_KSWAPD_RECLAIM)
336 #define GFP_NOIO	(__GFP_RECLAIM)
337 #define GFP_NOFS	(__GFP_RECLAIM | __GFP_IO)
338 #define GFP_USER	(__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
339 #define GFP_DMA		__GFP_DMA
340 #define GFP_DMA32	__GFP_DMA32
341 #define GFP_HIGHUSER	(GFP_USER | __GFP_HIGHMEM)
342 #define GFP_HIGHUSER_MOVABLE	(GFP_HIGHUSER | __GFP_MOVABLE | \
343 			 __GFP_SKIP_KASAN_POISON | __GFP_SKIP_KASAN_UNPOISON)
344 #define GFP_TRANSHUGE_LIGHT	((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \
345 			 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM)
346 #define GFP_TRANSHUGE	(GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM)
347 
348 #endif /* __LINUX_GFP_TYPES_H */
349