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_CMA 59 #define ___GFP_CMA 0x8000000u 60 #else 61 #define ___GFP_CMA 0 62 #endif 63 #ifdef CONFIG_LOCKDEP 64 #ifdef CONFIG_CMA 65 #define ___GFP_NOLOCKDEP 0x10000000u 66 #else 67 #define ___GFP_NOLOCKDEP 0x8000000u 68 #endif 69 #else 70 #define ___GFP_NOLOCKDEP 0 71 #endif 72 /* If the above are modified, __GFP_BITS_SHIFT may need updating */ 73 74 /* 75 * Physical address zone modifiers (see linux/mmzone.h - low four bits) 76 * 77 * Do not put any conditional on these. If necessary modify the definitions 78 * without the underscores and use them consistently. The definitions here may 79 * be used in bit comparisons. 80 */ 81 #define __GFP_DMA ((__force gfp_t)___GFP_DMA) 82 #define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) 83 #define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) 84 #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ 85 #define __GFP_CMA ((__force gfp_t)___GFP_CMA) 86 #define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE) 87 88 /** 89 * DOC: Page mobility and placement hints 90 * 91 * Page mobility and placement hints 92 * --------------------------------- 93 * 94 * These flags provide hints about how mobile the page is. Pages with similar 95 * mobility are placed within the same pageblocks to minimise problems due 96 * to external fragmentation. 97 * 98 * %__GFP_MOVABLE (also a zone modifier) indicates that the page can be 99 * moved by page migration during memory compaction or can be reclaimed. 100 * 101 * %__GFP_RECLAIMABLE is used for slab allocations that specify 102 * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers. 103 * 104 * %__GFP_WRITE indicates the caller intends to dirty the page. Where possible, 105 * these pages will be spread between local zones to avoid all the dirty 106 * pages being in one zone (fair zone allocation policy). 107 * 108 * %__GFP_HARDWALL enforces the cpuset memory allocation policy. 109 * 110 * %__GFP_THISNODE forces the allocation to be satisfied from the requested 111 * node with no fallbacks or placement policy enforcements. 112 * 113 * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg. 114 */ 115 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) 116 #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) 117 #define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL) 118 #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE) 119 #define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT) 120 121 /** 122 * DOC: Watermark modifiers 123 * 124 * Watermark modifiers -- controls access to emergency reserves 125 * ------------------------------------------------------------ 126 * 127 * %__GFP_HIGH indicates that the caller is high-priority and that granting 128 * the request is necessary before the system can make forward progress. 129 * For example, creating an IO context to clean pages. 130 * 131 * %__GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is 132 * high priority. Users are typically interrupt handlers. This may be 133 * used in conjunction with %__GFP_HIGH 134 * 135 * %__GFP_MEMALLOC allows access to all memory. This should only be used when 136 * the caller guarantees the allocation will allow more memory to be freed 137 * very shortly e.g. process exiting or swapping. Users either should 138 * be the MM or co-ordinating closely with the VM (e.g. swap over NFS). 139 * Users of this flag have to be extremely careful to not deplete the reserve 140 * completely and implement a throttling mechanism which controls the 141 * consumption of the reserve based on the amount of freed memory. 142 * Usage of a pre-allocated pool (e.g. mempool) should be always considered 143 * before using this flag. 144 * 145 * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. 146 * This takes precedence over the %__GFP_MEMALLOC flag if both are set. 147 */ 148 #define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC) 149 #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) 150 #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) 151 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) 152 153 /** 154 * DOC: Reclaim modifiers 155 * 156 * Reclaim modifiers 157 * ----------------- 158 * Please note that all the following flags are only applicable to sleepable 159 * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them). 160 * 161 * %__GFP_IO can start physical IO. 162 * 163 * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the 164 * allocator recursing into the filesystem which might already be holding 165 * locks. 166 * 167 * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim. 168 * This flag can be cleared to avoid unnecessary delays when a fallback 169 * option is available. 170 * 171 * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when 172 * the low watermark is reached and have it reclaim pages until the high 173 * watermark is reached. A caller may wish to clear this flag when fallback 174 * options are available and the reclaim is likely to disrupt the system. The 175 * canonical example is THP allocation where a fallback is cheap but 176 * reclaim/compaction may cause indirect stalls. 177 * 178 * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim. 179 * 180 * The default allocator behavior depends on the request size. We have a concept 181 * of so called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER). 182 * !costly allocations are too essential to fail so they are implicitly 183 * non-failing by default (with some exceptions like OOM victims might fail so 184 * the caller still has to check for failures) while costly requests try to be 185 * not disruptive and back off even without invoking the OOM killer. 186 * The following three modifiers might be used to override some of these 187 * implicit rules 188 * 189 * %__GFP_NORETRY: The VM implementation will try only very lightweight 190 * memory direct reclaim to get some memory under memory pressure (thus 191 * it can sleep). It will avoid disruptive actions like OOM killer. The 192 * caller must handle the failure which is quite likely to happen under 193 * heavy memory pressure. The flag is suitable when failure can easily be 194 * handled at small cost, such as reduced throughput 195 * 196 * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim 197 * procedures that have previously failed if there is some indication 198 * that progress has been made else where. It can wait for other 199 * tasks to attempt high level approaches to freeing memory such as 200 * compaction (which removes fragmentation) and page-out. 201 * There is still a definite limit to the number of retries, but it is 202 * a larger limit than with %__GFP_NORETRY. 203 * Allocations with this flag may fail, but only when there is 204 * genuinely little unused memory. While these allocations do not 205 * directly trigger the OOM killer, their failure indicates that 206 * the system is likely to need to use the OOM killer soon. The 207 * caller must handle failure, but can reasonably do so by failing 208 * a higher-level request, or completing it only in a much less 209 * efficient manner. 210 * If the allocation does fail, and the caller is in a position to 211 * free some non-essential memory, doing so could benefit the system 212 * as a whole. 213 * 214 * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller 215 * cannot handle allocation failures. The allocation could block 216 * indefinitely but will never return with failure. Testing for 217 * failure is pointless. 218 * New users should be evaluated carefully (and the flag should be 219 * used only when there is no reasonable failure policy) but it is 220 * definitely preferable to use the flag rather than opencode endless 221 * loop around allocator. 222 * Using this flag for costly allocations is _highly_ discouraged. 223 */ 224 #define __GFP_IO ((__force gfp_t)___GFP_IO) 225 #define __GFP_FS ((__force gfp_t)___GFP_FS) 226 #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */ 227 #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */ 228 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM)) 229 #define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL) 230 #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) 231 #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) 232 233 /** 234 * DOC: Action modifiers 235 * 236 * Action modifiers 237 * ---------------- 238 * 239 * %__GFP_NOWARN suppresses allocation failure reports. 240 * 241 * %__GFP_COMP address compound page metadata. 242 * 243 * %__GFP_ZERO returns a zeroed page on success. 244 * 245 * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself 246 * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that 247 * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting 248 * memory tags at the same time as zeroing memory has minimal additional 249 * performace impact. 250 * 251 * %__GFP_SKIP_KASAN_UNPOISON makes KASAN skip unpoisoning on page allocation. 252 * Only effective in HW_TAGS mode. 253 * 254 * %__GFP_SKIP_KASAN_POISON makes KASAN skip poisoning on page deallocation. 255 * Typically, used for userspace pages. Only effective in HW_TAGS mode. 256 */ 257 #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) 258 #define __GFP_COMP ((__force gfp_t)___GFP_COMP) 259 #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) 260 #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS) 261 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO) 262 #define __GFP_SKIP_KASAN_UNPOISON ((__force gfp_t)___GFP_SKIP_KASAN_UNPOISON) 263 #define __GFP_SKIP_KASAN_POISON ((__force gfp_t)___GFP_SKIP_KASAN_POISON) 264 265 /* Disable lockdep for GFP context tracking */ 266 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) 267 268 /* Room for N __GFP_FOO bits */ 269 #define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP) + IS_ENABLED(CONFIG_CMA)) 270 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) 271 272 /** 273 * DOC: Useful GFP flag combinations 274 * 275 * Useful GFP flag combinations 276 * ---------------------------- 277 * 278 * Useful GFP flag combinations that are commonly used. It is recommended 279 * that subsystems start with one of these combinations and then set/clear 280 * %__GFP_FOO flags as necessary. 281 * 282 * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower 283 * watermark is applied to allow access to "atomic reserves". 284 * The current implementation doesn't support NMI and few other strict 285 * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT. 286 * 287 * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires 288 * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim. 289 * 290 * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is 291 * accounted to kmemcg. 292 * 293 * %GFP_NOWAIT is for kernel allocations that should not stall for direct 294 * reclaim, start physical IO or use any filesystem callback. 295 * 296 * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages 297 * that do not require the starting of any physical IO. 298 * Please try to avoid using this flag directly and instead use 299 * memalloc_noio_{save,restore} to mark the whole scope which cannot 300 * perform any IO with a short explanation why. All allocation requests 301 * will inherit GFP_NOIO implicitly. 302 * 303 * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces. 304 * Please try to avoid using this flag directly and instead use 305 * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't 306 * recurse into the FS layer with a short explanation why. All allocation 307 * requests will inherit GFP_NOFS implicitly. 308 * 309 * %GFP_USER is for userspace allocations that also need to be directly 310 * accessibly by the kernel or hardware. It is typically used by hardware 311 * for buffers that are mapped to userspace (e.g. graphics) that hardware 312 * still must DMA to. cpuset limits are enforced for these allocations. 313 * 314 * %GFP_DMA exists for historical reasons and should be avoided where possible. 315 * The flags indicates that the caller requires that the lowest zone be 316 * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but 317 * it would require careful auditing as some users really require it and 318 * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the 319 * lowest zone as a type of emergency reserve. 320 * 321 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit 322 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory 323 * because the DMA32 kmalloc cache array is not implemented. 324 * (Reason: there is no such user in kernel). 325 * 326 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace, 327 * do not need to be directly accessible by the kernel but that cannot 328 * move once in use. An example may be a hardware allocation that maps 329 * data directly into userspace but has no addressing limitations. 330 * 331 * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not 332 * need direct access to but can use kmap() when access is required. They 333 * are expected to be movable via page reclaim or page migration. Typically, 334 * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE. 335 * 336 * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They 337 * are compound allocations that will generally fail quickly if memory is not 338 * available and will not wake kswapd/kcompactd on failure. The _LIGHT 339 * version does not attempt reclaim/compaction at all and is by default used 340 * in page fault path, while the non-light is used by khugepaged. 341 */ 342 #define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM) 343 #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) 344 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) 345 #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) 346 #define GFP_NOIO (__GFP_RECLAIM) 347 #define GFP_NOFS (__GFP_RECLAIM | __GFP_IO) 348 #define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL) 349 #define GFP_DMA __GFP_DMA 350 #define GFP_DMA32 __GFP_DMA32 351 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) 352 #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | \ 353 __GFP_SKIP_KASAN_POISON | __GFP_SKIP_KASAN_UNPOISON) 354 #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ 355 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM) 356 #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) 357 358 #endif /* __LINUX_GFP_TYPES_H */ 359