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 enum { 25 ___GFP_DMA_BIT, 26 ___GFP_HIGHMEM_BIT, 27 ___GFP_DMA32_BIT, 28 ___GFP_MOVABLE_BIT, 29 ___GFP_RECLAIMABLE_BIT, 30 ___GFP_HIGH_BIT, 31 ___GFP_IO_BIT, 32 ___GFP_FS_BIT, 33 ___GFP_ZERO_BIT, 34 ___GFP_UNUSED_BIT, /* 0x200u unused */ 35 ___GFP_DIRECT_RECLAIM_BIT, 36 ___GFP_KSWAPD_RECLAIM_BIT, 37 ___GFP_WRITE_BIT, 38 ___GFP_NOWARN_BIT, 39 ___GFP_RETRY_MAYFAIL_BIT, 40 ___GFP_NOFAIL_BIT, 41 ___GFP_NORETRY_BIT, 42 ___GFP_MEMALLOC_BIT, 43 ___GFP_COMP_BIT, 44 ___GFP_NOMEMALLOC_BIT, 45 ___GFP_HARDWALL_BIT, 46 ___GFP_THISNODE_BIT, 47 ___GFP_ACCOUNT_BIT, 48 ___GFP_ZEROTAGS_BIT, 49 #ifdef CONFIG_KASAN_HW_TAGS 50 ___GFP_SKIP_ZERO_BIT, 51 ___GFP_SKIP_KASAN_BIT, 52 #endif 53 #ifdef CONFIG_LOCKDEP 54 ___GFP_NOLOCKDEP_BIT, 55 #endif 56 ___GFP_LAST_BIT 57 }; 58 59 /* Plain integer GFP bitmasks. Do not use this directly. */ 60 #define ___GFP_DMA BIT(___GFP_DMA_BIT) 61 #define ___GFP_HIGHMEM BIT(___GFP_HIGHMEM_BIT) 62 #define ___GFP_DMA32 BIT(___GFP_DMA32_BIT) 63 #define ___GFP_MOVABLE BIT(___GFP_MOVABLE_BIT) 64 #define ___GFP_RECLAIMABLE BIT(___GFP_RECLAIMABLE_BIT) 65 #define ___GFP_HIGH BIT(___GFP_HIGH_BIT) 66 #define ___GFP_IO BIT(___GFP_IO_BIT) 67 #define ___GFP_FS BIT(___GFP_FS_BIT) 68 #define ___GFP_ZERO BIT(___GFP_ZERO_BIT) 69 /* 0x200u unused */ 70 #define ___GFP_DIRECT_RECLAIM BIT(___GFP_DIRECT_RECLAIM_BIT) 71 #define ___GFP_KSWAPD_RECLAIM BIT(___GFP_KSWAPD_RECLAIM_BIT) 72 #define ___GFP_WRITE BIT(___GFP_WRITE_BIT) 73 #define ___GFP_NOWARN BIT(___GFP_NOWARN_BIT) 74 #define ___GFP_RETRY_MAYFAIL BIT(___GFP_RETRY_MAYFAIL_BIT) 75 #define ___GFP_NOFAIL BIT(___GFP_NOFAIL_BIT) 76 #define ___GFP_NORETRY BIT(___GFP_NORETRY_BIT) 77 #define ___GFP_MEMALLOC BIT(___GFP_MEMALLOC_BIT) 78 #define ___GFP_COMP BIT(___GFP_COMP_BIT) 79 #define ___GFP_NOMEMALLOC BIT(___GFP_NOMEMALLOC_BIT) 80 #define ___GFP_HARDWALL BIT(___GFP_HARDWALL_BIT) 81 #define ___GFP_THISNODE BIT(___GFP_THISNODE_BIT) 82 #define ___GFP_ACCOUNT BIT(___GFP_ACCOUNT_BIT) 83 #define ___GFP_ZEROTAGS BIT(___GFP_ZEROTAGS_BIT) 84 #ifdef CONFIG_KASAN_HW_TAGS 85 #define ___GFP_SKIP_ZERO BIT(___GFP_SKIP_ZERO_BIT) 86 #define ___GFP_SKIP_KASAN BIT(___GFP_SKIP_KASAN_BIT) 87 #else 88 #define ___GFP_SKIP_ZERO 0 89 #define ___GFP_SKIP_KASAN 0 90 #endif 91 #ifdef CONFIG_LOCKDEP 92 #define ___GFP_NOLOCKDEP BIT(___GFP_NOLOCKDEP_BIT) 93 #else 94 #define ___GFP_NOLOCKDEP 0 95 #endif 96 97 /* 98 * Physical address zone modifiers (see linux/mmzone.h - low four bits) 99 * 100 * Do not put any conditional on these. If necessary modify the definitions 101 * without the underscores and use them consistently. The definitions here may 102 * be used in bit comparisons. 103 */ 104 #define __GFP_DMA ((__force gfp_t)___GFP_DMA) 105 #define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) 106 #define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) 107 #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ 108 #define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE) 109 110 /** 111 * DOC: Page mobility and placement hints 112 * 113 * Page mobility and placement hints 114 * --------------------------------- 115 * 116 * These flags provide hints about how mobile the page is. Pages with similar 117 * mobility are placed within the same pageblocks to minimise problems due 118 * to external fragmentation. 119 * 120 * %__GFP_MOVABLE (also a zone modifier) indicates that the page can be 121 * moved by page migration during memory compaction or can be reclaimed. 122 * 123 * %__GFP_RECLAIMABLE is used for slab allocations that specify 124 * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers. 125 * 126 * %__GFP_WRITE indicates the caller intends to dirty the page. Where possible, 127 * these pages will be spread between local zones to avoid all the dirty 128 * pages being in one zone (fair zone allocation policy). 129 * 130 * %__GFP_HARDWALL enforces the cpuset memory allocation policy. 131 * 132 * %__GFP_THISNODE forces the allocation to be satisfied from the requested 133 * node with no fallbacks or placement policy enforcements. 134 * 135 * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg. 136 */ 137 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) 138 #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) 139 #define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL) 140 #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE) 141 #define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT) 142 143 /** 144 * DOC: Watermark modifiers 145 * 146 * Watermark modifiers -- controls access to emergency reserves 147 * ------------------------------------------------------------ 148 * 149 * %__GFP_HIGH indicates that the caller is high-priority and that granting 150 * the request is necessary before the system can make forward progress. 151 * For example creating an IO context to clean pages and requests 152 * from atomic context. 153 * 154 * %__GFP_MEMALLOC allows access to all memory. This should only be used when 155 * the caller guarantees the allocation will allow more memory to be freed 156 * very shortly e.g. process exiting or swapping. Users either should 157 * be the MM or co-ordinating closely with the VM (e.g. swap over NFS). 158 * Users of this flag have to be extremely careful to not deplete the reserve 159 * completely and implement a throttling mechanism which controls the 160 * consumption of the reserve based on the amount of freed memory. 161 * Usage of a pre-allocated pool (e.g. mempool) should be always considered 162 * before using this flag. 163 * 164 * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. 165 * This takes precedence over the %__GFP_MEMALLOC flag if both are set. 166 */ 167 #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) 168 #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) 169 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) 170 171 /** 172 * DOC: Reclaim modifiers 173 * 174 * Reclaim modifiers 175 * ----------------- 176 * Please note that all the following flags are only applicable to sleepable 177 * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them). 178 * 179 * %__GFP_IO can start physical IO. 180 * 181 * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the 182 * allocator recursing into the filesystem which might already be holding 183 * locks. 184 * 185 * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim. 186 * This flag can be cleared to avoid unnecessary delays when a fallback 187 * option is available. 188 * 189 * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when 190 * the low watermark is reached and have it reclaim pages until the high 191 * watermark is reached. A caller may wish to clear this flag when fallback 192 * options are available and the reclaim is likely to disrupt the system. The 193 * canonical example is THP allocation where a fallback is cheap but 194 * reclaim/compaction may cause indirect stalls. 195 * 196 * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim. 197 * 198 * The default allocator behavior depends on the request size. We have a concept 199 * of so-called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER). 200 * !costly allocations are too essential to fail so they are implicitly 201 * non-failing by default (with some exceptions like OOM victims might fail so 202 * the caller still has to check for failures) while costly requests try to be 203 * not disruptive and back off even without invoking the OOM killer. 204 * The following three modifiers might be used to override some of these 205 * implicit rules. 206 * 207 * %__GFP_NORETRY: The VM implementation will try only very lightweight 208 * memory direct reclaim to get some memory under memory pressure (thus 209 * it can sleep). It will avoid disruptive actions like OOM killer. The 210 * caller must handle the failure which is quite likely to happen under 211 * heavy memory pressure. The flag is suitable when failure can easily be 212 * handled at small cost, such as reduced throughput. 213 * 214 * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim 215 * procedures that have previously failed if there is some indication 216 * that progress has been made elsewhere. It can wait for other 217 * tasks to attempt high-level approaches to freeing memory such as 218 * compaction (which removes fragmentation) and page-out. 219 * There is still a definite limit to the number of retries, but it is 220 * a larger limit than with %__GFP_NORETRY. 221 * Allocations with this flag may fail, but only when there is 222 * genuinely little unused memory. While these allocations do not 223 * directly trigger the OOM killer, their failure indicates that 224 * the system is likely to need to use the OOM killer soon. The 225 * caller must handle failure, but can reasonably do so by failing 226 * a higher-level request, or completing it only in a much less 227 * efficient manner. 228 * If the allocation does fail, and the caller is in a position to 229 * free some non-essential memory, doing so could benefit the system 230 * as a whole. 231 * 232 * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller 233 * cannot handle allocation failures. The allocation could block 234 * indefinitely but will never return with failure. Testing for 235 * failure is pointless. 236 * New users should be evaluated carefully (and the flag should be 237 * used only when there is no reasonable failure policy) but it is 238 * definitely preferable to use the flag rather than opencode endless 239 * loop around allocator. 240 * Using this flag for costly allocations is _highly_ discouraged. 241 */ 242 #define __GFP_IO ((__force gfp_t)___GFP_IO) 243 #define __GFP_FS ((__force gfp_t)___GFP_FS) 244 #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */ 245 #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */ 246 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM)) 247 #define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL) 248 #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) 249 #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) 250 251 /** 252 * DOC: Action modifiers 253 * 254 * Action modifiers 255 * ---------------- 256 * 257 * %__GFP_NOWARN suppresses allocation failure reports. 258 * 259 * %__GFP_COMP address compound page metadata. 260 * 261 * %__GFP_ZERO returns a zeroed page on success. 262 * 263 * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself 264 * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that 265 * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting 266 * memory tags at the same time as zeroing memory has minimal additional 267 * performance impact. 268 * 269 * %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation. 270 * Used for userspace and vmalloc pages; the latter are unpoisoned by 271 * kasan_unpoison_vmalloc instead. For userspace pages, results in 272 * poisoning being skipped as well, see should_skip_kasan_poison for 273 * details. Only effective in HW_TAGS mode. 274 */ 275 #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) 276 #define __GFP_COMP ((__force gfp_t)___GFP_COMP) 277 #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) 278 #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS) 279 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO) 280 #define __GFP_SKIP_KASAN ((__force gfp_t)___GFP_SKIP_KASAN) 281 282 /* Disable lockdep for GFP context tracking */ 283 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) 284 285 /* Room for N __GFP_FOO bits */ 286 #define __GFP_BITS_SHIFT ___GFP_LAST_BIT 287 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) 288 289 /** 290 * DOC: Useful GFP flag combinations 291 * 292 * Useful GFP flag combinations 293 * ---------------------------- 294 * 295 * Useful GFP flag combinations that are commonly used. It is recommended 296 * that subsystems start with one of these combinations and then set/clear 297 * %__GFP_FOO flags as necessary. 298 * 299 * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower 300 * watermark is applied to allow access to "atomic reserves". 301 * The current implementation doesn't support NMI and few other strict 302 * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT. 303 * 304 * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires 305 * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim. 306 * 307 * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is 308 * accounted to kmemcg. 309 * 310 * %GFP_NOWAIT is for kernel allocations that should not stall for direct 311 * reclaim, start physical IO or use any filesystem callback. It is very 312 * likely to fail to allocate memory, even for very small allocations. 313 * 314 * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages 315 * that do not require the starting of any physical IO. 316 * Please try to avoid using this flag directly and instead use 317 * memalloc_noio_{save,restore} to mark the whole scope which cannot 318 * perform any IO with a short explanation why. All allocation requests 319 * will inherit GFP_NOIO implicitly. 320 * 321 * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces. 322 * Please try to avoid using this flag directly and instead use 323 * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't 324 * recurse into the FS layer with a short explanation why. All allocation 325 * requests will inherit GFP_NOFS implicitly. 326 * 327 * %GFP_USER is for userspace allocations that also need to be directly 328 * accessibly by the kernel or hardware. It is typically used by hardware 329 * for buffers that are mapped to userspace (e.g. graphics) that hardware 330 * still must DMA to. cpuset limits are enforced for these allocations. 331 * 332 * %GFP_DMA exists for historical reasons and should be avoided where possible. 333 * The flags indicates that the caller requires that the lowest zone be 334 * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but 335 * it would require careful auditing as some users really require it and 336 * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the 337 * lowest zone as a type of emergency reserve. 338 * 339 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit 340 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory 341 * because the DMA32 kmalloc cache array is not implemented. 342 * (Reason: there is no such user in kernel). 343 * 344 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace, 345 * do not need to be directly accessible by the kernel but that cannot 346 * move once in use. An example may be a hardware allocation that maps 347 * data directly into userspace but has no addressing limitations. 348 * 349 * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not 350 * need direct access to but can use kmap() when access is required. They 351 * are expected to be movable via page reclaim or page migration. Typically, 352 * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE. 353 * 354 * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They 355 * are compound allocations that will generally fail quickly if memory is not 356 * available and will not wake kswapd/kcompactd on failure. The _LIGHT 357 * version does not attempt reclaim/compaction at all and is by default used 358 * in page fault path, while the non-light is used by khugepaged. 359 */ 360 #define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) 361 #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) 362 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) 363 #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM | __GFP_NOWARN) 364 #define GFP_NOIO (__GFP_RECLAIM) 365 #define GFP_NOFS (__GFP_RECLAIM | __GFP_IO) 366 #define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL) 367 #define GFP_DMA __GFP_DMA 368 #define GFP_DMA32 __GFP_DMA32 369 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) 370 #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | __GFP_SKIP_KASAN) 371 #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ 372 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM) 373 #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) 374 375 #endif /* __LINUX_GFP_TYPES_H */ 376