1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_GFP_TYPES_H 3 #define __LINUX_GFP_TYPES_H 4 5 #include <linux/bits.h> 6 7 /* The typedef is in types.h but we want the documentation here */ 8 #if 0 9 /** 10 * typedef gfp_t - Memory allocation flags. 11 * 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``. 17 */ 18 typedef unsigned int __bitwise gfp_t; 19 #endif 20 21 /* 22 * In case of changes, please don't forget to update 23 * include/trace/events/mmflags.h and tools/perf/builtin-kmem.c 24 */ 25 26 /* Plain integer GFP bitmasks. Do not use this directly. */ 27 #define ___GFP_DMA 0x01u 28 #define ___GFP_HIGHMEM 0x02u 29 #define ___GFP_DMA32 0x04u 30 #define ___GFP_MOVABLE 0x08u 31 #define ___GFP_RECLAIMABLE 0x10u 32 #define ___GFP_HIGH 0x20u 33 #define ___GFP_IO 0x40u 34 #define ___GFP_FS 0x80u 35 #define ___GFP_ZERO 0x100u 36 /* 0x200u unused */ 37 #define ___GFP_DIRECT_RECLAIM 0x400u 38 #define ___GFP_KSWAPD_RECLAIM 0x800u 39 #define ___GFP_WRITE 0x1000u 40 #define ___GFP_NOWARN 0x2000u 41 #define ___GFP_RETRY_MAYFAIL 0x4000u 42 #define ___GFP_NOFAIL 0x8000u 43 #define ___GFP_NORETRY 0x10000u 44 #define ___GFP_MEMALLOC 0x20000u 45 #define ___GFP_COMP 0x40000u 46 #define ___GFP_NOMEMALLOC 0x80000u 47 #define ___GFP_HARDWALL 0x100000u 48 #define ___GFP_THISNODE 0x200000u 49 #define ___GFP_ACCOUNT 0x400000u 50 #define ___GFP_ZEROTAGS 0x800000u 51 #ifdef CONFIG_KASAN_HW_TAGS 52 #define ___GFP_SKIP_ZERO 0x1000000u 53 #define ___GFP_SKIP_KASAN 0x2000000u 54 #else 55 #define ___GFP_SKIP_ZERO 0 56 #define ___GFP_SKIP_KASAN 0 57 #endif 58 59 #ifdef CONFIG_CMA 60 #define ___GFP_CMA 0x4000000u 61 #else 62 #define ___GFP_CMA 0 63 #endif 64 65 #ifdef CONFIG_LOCKDEP 66 #ifdef CONFIG_CMA 67 #define ___GFP_NOLOCKDEP 0x8000000u 68 #else 69 #define ___GFP_NOLOCKDEP 0x4000000u 70 #endif 71 #else 72 #define ___GFP_NOLOCKDEP 0 73 #endif 74 /* If the above are modified, __GFP_BITS_SHIFT may need updating */ 75 76 /* 77 * Physical address zone modifiers (see linux/mmzone.h - low four bits) 78 * 79 * Do not put any conditional on these. If necessary modify the definitions 80 * without the underscores and use them consistently. The definitions here may 81 * be used in bit comparisons. 82 */ 83 #define __GFP_DMA ((__force gfp_t)___GFP_DMA) 84 #define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM) 85 #define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32) 86 #define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */ 87 #define __GFP_CMA ((__force gfp_t)___GFP_CMA) 88 #define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE) 89 90 /** 91 * DOC: Page mobility and placement hints 92 * 93 * Page mobility and placement hints 94 * --------------------------------- 95 * 96 * These flags provide hints about how mobile the page is. Pages with similar 97 * mobility are placed within the same pageblocks to minimise problems due 98 * to external fragmentation. 99 * 100 * %__GFP_MOVABLE (also a zone modifier) indicates that the page can be 101 * moved by page migration during memory compaction or can be reclaimed. 102 * 103 * %__GFP_RECLAIMABLE is used for slab allocations that specify 104 * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers. 105 * 106 * %__GFP_WRITE indicates the caller intends to dirty the page. Where possible, 107 * these pages will be spread between local zones to avoid all the dirty 108 * pages being in one zone (fair zone allocation policy). 109 * 110 * %__GFP_HARDWALL enforces the cpuset memory allocation policy. 111 * 112 * %__GFP_THISNODE forces the allocation to be satisfied from the requested 113 * node with no fallbacks or placement policy enforcements. 114 * 115 * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg. 116 */ 117 #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) 118 #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) 119 #define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL) 120 #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE) 121 #define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT) 122 123 /** 124 * DOC: Watermark modifiers 125 * 126 * Watermark modifiers -- controls access to emergency reserves 127 * ------------------------------------------------------------ 128 * 129 * %__GFP_HIGH indicates that the caller is high-priority and that granting 130 * the request is necessary before the system can make forward progress. 131 * For example creating an IO context to clean pages and requests 132 * from atomic context. 133 * 134 * %__GFP_MEMALLOC allows access to all memory. This should only be used when 135 * the caller guarantees the allocation will allow more memory to be freed 136 * very shortly e.g. process exiting or swapping. Users either should 137 * be the MM or co-ordinating closely with the VM (e.g. swap over NFS). 138 * Users of this flag have to be extremely careful to not deplete the reserve 139 * completely and implement a throttling mechanism which controls the 140 * consumption of the reserve based on the amount of freed memory. 141 * Usage of a pre-allocated pool (e.g. mempool) should be always considered 142 * before using this flag. 143 * 144 * %__GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves. 145 * This takes precedence over the %__GFP_MEMALLOC flag if both are set. 146 */ 147 #define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) 148 #define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC) 149 #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) 150 151 /** 152 * DOC: Reclaim modifiers 153 * 154 * Reclaim modifiers 155 * ----------------- 156 * Please note that all the following flags are only applicable to sleepable 157 * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them). 158 * 159 * %__GFP_IO can start physical IO. 160 * 161 * %__GFP_FS can call down to the low-level FS. Clearing the flag avoids the 162 * allocator recursing into the filesystem which might already be holding 163 * locks. 164 * 165 * %__GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim. 166 * This flag can be cleared to avoid unnecessary delays when a fallback 167 * option is available. 168 * 169 * %__GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when 170 * the low watermark is reached and have it reclaim pages until the high 171 * watermark is reached. A caller may wish to clear this flag when fallback 172 * options are available and the reclaim is likely to disrupt the system. The 173 * canonical example is THP allocation where a fallback is cheap but 174 * reclaim/compaction may cause indirect stalls. 175 * 176 * %__GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim. 177 * 178 * The default allocator behavior depends on the request size. We have a concept 179 * of so called costly allocations (with order > %PAGE_ALLOC_COSTLY_ORDER). 180 * !costly allocations are too essential to fail so they are implicitly 181 * non-failing by default (with some exceptions like OOM victims might fail so 182 * the caller still has to check for failures) while costly requests try to be 183 * not disruptive and back off even without invoking the OOM killer. 184 * The following three modifiers might be used to override some of these 185 * implicit rules 186 * 187 * %__GFP_NORETRY: The VM implementation will try only very lightweight 188 * memory direct reclaim to get some memory under memory pressure (thus 189 * it can sleep). It will avoid disruptive actions like OOM killer. The 190 * caller must handle the failure which is quite likely to happen under 191 * heavy memory pressure. The flag is suitable when failure can easily be 192 * handled at small cost, such as reduced throughput 193 * 194 * %__GFP_RETRY_MAYFAIL: The VM implementation will retry memory reclaim 195 * procedures that have previously failed if there is some indication 196 * that progress has been made else where. It can wait for other 197 * tasks to attempt high level approaches to freeing memory such as 198 * compaction (which removes fragmentation) and page-out. 199 * There is still a definite limit to the number of retries, but it is 200 * a larger limit than with %__GFP_NORETRY. 201 * Allocations with this flag may fail, but only when there is 202 * genuinely little unused memory. While these allocations do not 203 * directly trigger the OOM killer, their failure indicates that 204 * the system is likely to need to use the OOM killer soon. The 205 * caller must handle failure, but can reasonably do so by failing 206 * a higher-level request, or completing it only in a much less 207 * efficient manner. 208 * If the allocation does fail, and the caller is in a position to 209 * free some non-essential memory, doing so could benefit the system 210 * as a whole. 211 * 212 * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller 213 * cannot handle allocation failures. The allocation could block 214 * indefinitely but will never return with failure. Testing for 215 * failure is pointless. 216 * New users should be evaluated carefully (and the flag should be 217 * used only when there is no reasonable failure policy) but it is 218 * definitely preferable to use the flag rather than opencode endless 219 * loop around allocator. 220 * Using this flag for costly allocations is _highly_ discouraged. 221 */ 222 #define __GFP_IO ((__force gfp_t)___GFP_IO) 223 #define __GFP_FS ((__force gfp_t)___GFP_FS) 224 #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */ 225 #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */ 226 #define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM)) 227 #define __GFP_RETRY_MAYFAIL ((__force gfp_t)___GFP_RETRY_MAYFAIL) 228 #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) 229 #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) 230 231 /** 232 * DOC: Action modifiers 233 * 234 * Action modifiers 235 * ---------------- 236 * 237 * %__GFP_NOWARN suppresses allocation failure reports. 238 * 239 * %__GFP_COMP address compound page metadata. 240 * 241 * %__GFP_ZERO returns a zeroed page on success. 242 * 243 * %__GFP_ZEROTAGS zeroes memory tags at allocation time if the memory itself 244 * is being zeroed (either via __GFP_ZERO or via init_on_alloc, provided that 245 * __GFP_SKIP_ZERO is not set). This flag is intended for optimization: setting 246 * memory tags at the same time as zeroing memory has minimal additional 247 * performace impact. 248 * 249 * %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation. 250 * Used for userspace and vmalloc pages; the latter are unpoisoned by 251 * kasan_unpoison_vmalloc instead. For userspace pages, results in 252 * poisoning being skipped as well, see should_skip_kasan_poison for 253 * details. Only effective in HW_TAGS mode. 254 */ 255 #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) 256 #define __GFP_COMP ((__force gfp_t)___GFP_COMP) 257 #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) 258 #define __GFP_ZEROTAGS ((__force gfp_t)___GFP_ZEROTAGS) 259 #define __GFP_SKIP_ZERO ((__force gfp_t)___GFP_SKIP_ZERO) 260 #define __GFP_SKIP_KASAN ((__force gfp_t)___GFP_SKIP_KASAN) 261 262 /* Disable lockdep for GFP context tracking */ 263 #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) 264 265 /* Room for N __GFP_FOO bits */ 266 #define __GFP_BITS_SHIFT (26 + IS_ENABLED(CONFIG_LOCKDEP) + IS_ENABLED(CONFIG_CMA)) 267 #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) 268 269 /** 270 * DOC: Useful GFP flag combinations 271 * 272 * Useful GFP flag combinations 273 * ---------------------------- 274 * 275 * Useful GFP flag combinations that are commonly used. It is recommended 276 * that subsystems start with one of these combinations and then set/clear 277 * %__GFP_FOO flags as necessary. 278 * 279 * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower 280 * watermark is applied to allow access to "atomic reserves". 281 * The current implementation doesn't support NMI and few other strict 282 * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT. 283 * 284 * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires 285 * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim. 286 * 287 * %GFP_KERNEL_ACCOUNT is the same as GFP_KERNEL, except the allocation is 288 * accounted to kmemcg. 289 * 290 * %GFP_NOWAIT is for kernel allocations that should not stall for direct 291 * reclaim, start physical IO or use any filesystem callback. 292 * 293 * %GFP_NOIO will use direct reclaim to discard clean pages or slab pages 294 * that do not require the starting of any physical IO. 295 * Please try to avoid using this flag directly and instead use 296 * memalloc_noio_{save,restore} to mark the whole scope which cannot 297 * perform any IO with a short explanation why. All allocation requests 298 * will inherit GFP_NOIO implicitly. 299 * 300 * %GFP_NOFS will use direct reclaim but will not use any filesystem interfaces. 301 * Please try to avoid using this flag directly and instead use 302 * memalloc_nofs_{save,restore} to mark the whole scope which cannot/shouldn't 303 * recurse into the FS layer with a short explanation why. All allocation 304 * requests will inherit GFP_NOFS implicitly. 305 * 306 * %GFP_USER is for userspace allocations that also need to be directly 307 * accessibly by the kernel or hardware. It is typically used by hardware 308 * for buffers that are mapped to userspace (e.g. graphics) that hardware 309 * still must DMA to. cpuset limits are enforced for these allocations. 310 * 311 * %GFP_DMA exists for historical reasons and should be avoided where possible. 312 * The flags indicates that the caller requires that the lowest zone be 313 * used (%ZONE_DMA or 16M on x86-64). Ideally, this would be removed but 314 * it would require careful auditing as some users really require it and 315 * others use the flag to avoid lowmem reserves in %ZONE_DMA and treat the 316 * lowest zone as a type of emergency reserve. 317 * 318 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit 319 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory 320 * because the DMA32 kmalloc cache array is not implemented. 321 * (Reason: there is no such user in kernel). 322 * 323 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace, 324 * do not need to be directly accessible by the kernel but that cannot 325 * move once in use. An example may be a hardware allocation that maps 326 * data directly into userspace but has no addressing limitations. 327 * 328 * %GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not 329 * need direct access to but can use kmap() when access is required. They 330 * are expected to be movable via page reclaim or page migration. Typically, 331 * pages on the LRU would also be allocated with %GFP_HIGHUSER_MOVABLE. 332 * 333 * %GFP_TRANSHUGE and %GFP_TRANSHUGE_LIGHT are used for THP allocations. They 334 * are compound allocations that will generally fail quickly if memory is not 335 * available and will not wake kswapd/kcompactd on failure. The _LIGHT 336 * version does not attempt reclaim/compaction at all and is by default used 337 * in page fault path, while the non-light is used by khugepaged. 338 */ 339 #define GFP_ATOMIC (__GFP_HIGH|__GFP_KSWAPD_RECLAIM) 340 #define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS) 341 #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT) 342 #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM) 343 #define GFP_NOIO (__GFP_RECLAIM) 344 #define GFP_NOFS (__GFP_RECLAIM | __GFP_IO) 345 #define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL) 346 #define GFP_DMA __GFP_DMA 347 #define GFP_DMA32 __GFP_DMA32 348 #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM) 349 #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE | __GFP_SKIP_KASAN) 350 #define GFP_TRANSHUGE_LIGHT ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \ 351 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM) 352 #define GFP_TRANSHUGE (GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM) 353 354 #endif /* __LINUX_GFP_TYPES_H */ 355