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 /* 0x200u unused */ 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 and requests 120 * from atomic context. 121 * 122 * %__GFP_MEMALLOC allows access to all memory. This should only be used when 123 * the caller guarantees the allocation will allow more memory to be freed 124 * very shortly e.g. process exiting or swapping. Users either should 125 * be the MM or co-ordinating closely with the VM (e.g. swap over NFS). 126 * Users of this flag have to be extremely careful to not deplete the reserve 127 * completely and implement a throttling mechanism which controls the 128 * consumption of the reserve based on the amount of freed memory. 129 * Usage of a pre-allocated pool (e.g. mempool) should be always considered 130 * before using this flag. 131 * 132 * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. 133 * This takes precedence over the %__GFP_MEMALLOC flag if both are set. 134 */ 135 #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) 136 #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) 137 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) 138 139 /** 140 * DOC: Reclaim modifiers 141 * 142 * Reclaim modifiers 143 * ----------------- 144 * Please note that all the following flags are only applicable to sleepable 145 * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them). 146 * 147 * %__GFP_IO can start physical IO. 148 * 149 * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the 150 * allocator recursing into the filesystem which might already be holding 151 * locks. 152 * 153 * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim. 154 * This flag can be cleared to avoid unnecessary delays when a fallback 155 * option is available. 156 * 157 * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when 158 * the low watermark is reached and have it reclaim pages until the high 159 * watermark is reached. A caller may wish to clear this flag when fallback 160 * options are available and the reclaim is likely to disrupt the system. The 161 * canonical example is THP allocation where a fallback is cheap but 162 * reclaim/compaction may cause indirect stalls. 163 * 164 * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim. 165 * 166 * The default allocator behavior depends on the request size. We have a concept 167 * of so called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER). 168 * !costly allocations are too essential to fail so they are implicitly 169 * non-failing by default (with some exceptions like OOM victims might fail so 170 * the caller still has to check for failures) while costly requests try to be 171 * not disruptive and back off even without invoking the OOM killer. 172 * The following three modifiers might be used to override some of these 173 * implicit rules 174 * 175 * %__GFP_NORETRY: The VM implementation will try only very lightweight 176 * memory direct reclaim to get some memory under memory pressure (thus 177 * it can sleep). It will avoid disruptive actions like OOM killer. The 178 * caller must handle the failure which is quite likely to happen under 179 * heavy memory pressure. The flag is suitable when failure can easily be 180 * handled at small cost, such as reduced throughput 181 * 182 * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim 183 * procedures that have previously failed if there is some indication 184 * that progress has been made else where. It can wait for other 185 * tasks to attempt high level approaches to freeing memory such as 186 * compaction (which removes fragmentation) and page-out. 187 * There is still a definite limit to the number of retries, but it is 188 * a larger limit than with %__GFP_NORETRY. 189 * Allocations with this flag may fail, but only when there is 190 * genuinely little unused memory. While these allocations do not 191 * directly trigger the OOM killer, their failure indicates that 192 * the system is likely to need to use the OOM killer soon. The 193 * caller must handle failure, but can reasonably do so by failing 194 * a higher-level request, or completing it only in a much less 195 * efficient manner. 196 * If the allocation does fail, and the caller is in a position to 197 * free some non-essential memory, doing so could benefit the system 198 * as a whole. 199 * 200 * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller 201 * cannot handle allocation failures. The allocation could block 202 * indefinitely but will never return with failure. Testing for 203 * failure is pointless. 204 * New users should be evaluated carefully (and the flag should be 205 * used only when there is no reasonable failure policy) but it is 206 * definitely preferable to use the flag rather than opencode endless 207 * loop around allocator. 208 * Using this flag for costly allocations is _highly_ discouraged. 209 */ 210 #define __GFP_IO ((__force gfp_t)___GFP_IO) 211 #define __GFP_FS ((__force gfp_t)___GFP_FS) 212 #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */ 213 #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */ 214 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM)) 215 #define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL) 216 #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) 217 #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) 218 219 /** 220 * DOC: Action modifiers 221 * 222 * Action modifiers 223 * ---------------- 224 * 225 * %__GFP_NOWARN suppresses allocation failure reports. 226 * 227 * %__GFP_COMP address compound page metadata. 228 * 229 * %__GFP_ZERO returns a zeroed page on success. 230 * 231 * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself 232 * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that 233 * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting 234 * memory tags at the same time as zeroing memory has minimal additional 235 * performace impact. 236 * 237 * %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation. 238 * Only effective in HW_TAGS mode. 239 * 240 * %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation. 241 * Typically, used for userspace pages. Only effective in HW_TAGS mode. 242 */ 243 #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) 244 #define __GFP_COMP ((__force gfp_t)___GFP_COMP) 245 #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) 246 #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS) 247 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO) 248 #define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON) 249 #define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON) 250 251 /* Disable lockdep for GFP context tracking */ 252 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) 253 254 /* Room for N __GFP_FOO bits */ 255 #define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP)) 256 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) 257 258 /** 259 * DOC: Useful GFP flag combinations 260 * 261 * Useful GFP flag combinations 262 * ---------------------------- 263 * 264 * Useful GFP flag combinations that are commonly used. It is recommended 265 * that subsystems start with one of these combinations and then set/clear 266 * %__GFP_FOO flags as necessary. 267 * 268 * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower 269 * watermark is applied to allow access to "atomic reserves". 270 * The current implementation doesn't support NMI and few other strict 271 * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT. 272 * 273 * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires 274 * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim. 275 * 276 * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is 277 * accounted to kmemcg. 278 * 279 * %GFP_NOWAIT is for kernel allocations that should not stall for direct 280 * reclaim, start physical IO or use any filesystem callback. 281 * 282 * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages 283 * that do not require the starting of any physical IO. 284 * Please try to avoid using this flag directly and instead use 285 * memalloc_noio_{save,restore} to mark the whole scope which cannot 286 * perform any IO with a short explanation why. All allocation requests 287 * will inherit GFP_NOIO implicitly. 288 * 289 * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces. 290 * Please try to avoid using this flag directly and instead use 291 * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't 292 * recurse into the FS layer with a short explanation why. All allocation 293 * requests will inherit GFP_NOFS implicitly. 294 * 295 * %GFP_USER is for userspace allocations that also need to be directly 296 * accessibly by the kernel or hardware. It is typically used by hardware 297 * for buffers that are mapped to userspace (e.g. graphics) that hardware 298 * still must DMA to. cpuset limits are enforced for these allocations. 299 * 300 * %GFP_DMA exists for historical reasons and should be avoided where possible. 301 * The flags indicates that the caller requires that the lowest zone be 302 * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but 303 * it would require careful auditing as some users really require it and 304 * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the 305 * lowest zone as a type of emergency reserve. 306 * 307 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit 308 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory 309 * because the DMA32 kmalloc cache array is not implemented. 310 * (Reason: there is no such user in kernel). 311 * 312 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace, 313 * do not need to be directly accessible by the kernel but that cannot 314 * move once in use. An example may be a hardware allocation that maps 315 * data directly into userspace but has no addressing limitations. 316 * 317 * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not 318 * need direct access to but can use kmap() when access is required. They 319 * are expected to be movable via page reclaim or page migration. Typically, 320 * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE. 321 * 322 * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They 323 * are compound allocations that will generally fail quickly if memory is not 324 * available and will not wake kswapd/kcompactd on failure. The _LIGHT 325 * version does not attempt reclaim/compaction at all and is by default used 326 * in page fault path, while the non-light is used by khugepaged. 327 */ 328 #define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) 329 #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) 330 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) 331 #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) 332 #define GFP_NOIO (__GFP_RECLAIM) 333 #define GFP_NOFS (__GFP_RECLAIM | __GFP_IO) 334 #define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL) 335 #define GFP_DMA __GFP_DMA 336 #define GFP_DMA32 __GFP_DMA32 337 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) 338 #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | \ 339 __GFP_SKIP_KASAN_POISON | __GFP_SKIP_KASAN_UNPOISON) 340 #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ 341 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM) 342 #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) 343 344 #endif /* __LINUX_GFP_TYPES_H */ 345