/* If the above are modified, __GFP_BITS_SHIFT may need updating */
/*
- * GFP bitmasks..
- *
- * Zone modifiers (see linux/mmzone.h - low three bits)
+ * Physical address zone modifiers (see linux/mmzone.h - low four bits)
*
* Do not put any conditional on these. If necessary modify the definitions
* without the underscores and use them consistently. The definitions here may
#define __GFP_HIGHMEM ((__force gfp_t)___GFP_HIGHMEM)
#define __GFP_DMA32 ((__force gfp_t)___GFP_DMA32)
#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* Page is movable */
+#define __GFP_MOVABLE ((__force gfp_t)___GFP_MOVABLE) /* ZONE_MOVABLE allowed */
#define GFP_ZONEMASK (__GFP_DMA|__GFP_HIGHMEM|__GFP_DMA32|__GFP_MOVABLE)
+
/*
- * Action modifiers - doesn't change the zoning
+ * Page mobility and placement hints
*
- * __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt
- * _might_ fail. This depends upon the particular VM implementation.
+ * These flags provide hints about how mobile the page is. Pages with similar
+ * mobility are placed within the same pageblocks to minimise problems due
+ * to external fragmentation.
*
- * __GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
- * cannot handle allocation failures. New users should be evaluated carefully
- * (and the flag should be used only when there is no reasonable failure policy)
- * but it is definitely preferable to use the flag rather than opencode endless
- * loop around allocator.
+ * __GFP_MOVABLE (also a zone modifier) indicates that the page can be
+ * moved by page migration during memory compaction or can be reclaimed.
*
- * __GFP_NORETRY: The VM implementation must not retry indefinitely and will
- * return NULL when direct reclaim and memory compaction have failed to allow
- * the allocation to succeed. The OOM killer is not called with the current
- * implementation.
+ * __GFP_RECLAIMABLE is used for slab allocations that specify
+ * SLAB_RECLAIM_ACCOUNT and whose pages can be freed via shrinkers.
+ *
+ * __GFP_WRITE indicates the caller intends to dirty the page. Where possible,
+ * these pages will be spread between local zones to avoid all the dirty
+ * pages being in one zone (fair zone allocation policy).
*
- * __GFP_MOVABLE: Flag that this page will be movable by the page migration
- * mechanism or reclaimed
+ * __GFP_HARDWALL enforces the cpuset memory allocation policy.
+ *
+ * __GFP_THISNODE forces the allocation to be satisified from the requested
+ * node with no fallbacks or placement policy enforcements.
*/
-#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC) /* Caller cannot wait or reschedule */
-#define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) /* Should access emergency pools? */
-#define __GFP_IO ((__force gfp_t)___GFP_IO) /* Can start physical IO? */
-#define __GFP_FS ((__force gfp_t)___GFP_FS) /* Can call down to low-level FS? */
-#define __GFP_COLD ((__force gfp_t)___GFP_COLD) /* Cache-cold page required */
-#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) /* Suppress page allocation failure warning */
-#define __GFP_REPEAT ((__force gfp_t)___GFP_REPEAT) /* See above */
-#define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) /* See above */
-#define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) /* See above */
-#define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)/* Allow access to emergency reserves */
-#define __GFP_COMP ((__force gfp_t)___GFP_COMP) /* Add compound page metadata */
-#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) /* Return zeroed page on success */
-#define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) /* Don't use emergency reserves.
- * This takes precedence over the
- * __GFP_MEMALLOC flag if both are
- * set
- */
-#define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL) /* Enforce hardwall cpuset memory allocs */
-#define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE)/* No fallback, no policies */
-#define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) /* Page is reclaimable */
-#define __GFP_NOACCOUNT ((__force gfp_t)___GFP_NOACCOUNT) /* Don't account to kmemcg */
-#define __GFP_NOTRACK ((__force gfp_t)___GFP_NOTRACK) /* Don't track with kmemcheck */
-
-#define __GFP_OTHER_NODE ((__force gfp_t)___GFP_OTHER_NODE) /* On behalf of other node */
-#define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) /* Allocator intends to dirty page */
+#define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE)
+#define __GFP_WRITE ((__force gfp_t)___GFP_WRITE)
+#define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL)
+#define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE)
/*
- * A caller that is willing to wait may enter direct reclaim and will
- * wake kswapd to reclaim pages in the background until the high
- * watermark is met. A caller may wish to clear __GFP_DIRECT_RECLAIM to
- * avoid unnecessary delays when a fallback option is available but
- * still allow kswapd to reclaim in the background. The kswapd flag
- * can be cleared when the reclaiming of pages would cause unnecessary
- * disruption.
+ * Watermark modifiers -- controls access to emergency reserves
+ *
+ * __GFP_HIGH indicates that the caller is high-priority and that granting
+ * the request is necessary before the system can make forward progress.
+ * For example, creating an IO context to clean pages.
+ *
+ * __GFP_ATOMIC indicates that the caller cannot reclaim or sleep and is
+ * high priority. Users are typically interrupt handlers. This may be
+ * used in conjunction with __GFP_HIGH
+ *
+ * __GFP_MEMALLOC allows access to all memory. This should only be used when
+ * the caller guarantees the allocation will allow more memory to be freed
+ * very shortly e.g. process exiting or swapping. Users either should
+ * be the MM or co-ordinating closely with the VM (e.g. swap over NFS).
+ *
+ * __GFP_NOMEMALLOC is used to explicitly forbid access to emergency reserves.
+ * This takes precedence over the __GFP_MEMALLOC flag if both are set.
+ *
+ * __GFP_NOACCOUNT ignores the accounting for kmemcg limit enforcement.
*/
-#define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM))
+#define __GFP_ATOMIC ((__force gfp_t)___GFP_ATOMIC)
+#define __GFP_HIGH ((__force gfp_t)___GFP_HIGH)
+#define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)
+#define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC)
+#define __GFP_NOACCOUNT ((__force gfp_t)___GFP_NOACCOUNT)
+
+/*
+ * Reclaim modifiers
+ *
+ * __GFP_IO can start physical IO.
+ *
+ * __GFP_FS can call down to the low-level FS. Clearing the flag avoids the
+ * allocator recursing into the filesystem which might already be holding
+ * locks.
+ *
+ * __GFP_DIRECT_RECLAIM indicates that the caller may enter direct reclaim.
+ * This flag can be cleared to avoid unnecessary delays when a fallback
+ * option is available.
+ *
+ * __GFP_KSWAPD_RECLAIM indicates that the caller wants to wake kswapd when
+ * the low watermark is reached and have it reclaim pages until the high
+ * watermark is reached. A caller may wish to clear this flag when fallback
+ * options are available and the reclaim is likely to disrupt the system. The
+ * canonical example is THP allocation where a fallback is cheap but
+ * reclaim/compaction may cause indirect stalls.
+ *
+ * __GFP_RECLAIM is shorthand to allow/forbid both direct and kswapd reclaim.
+ *
+ * __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt
+ * _might_ fail. This depends upon the particular VM implementation.
+ *
+ * __GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
+ * cannot handle allocation failures. New users should be evaluated carefully
+ * (and the flag should be used only when there is no reasonable failure
+ * policy) but it is definitely preferable to use the flag rather than
+ * opencode endless loop around allocator.
+ *
+ * __GFP_NORETRY: The VM implementation must not retry indefinitely and will
+ * return NULL when direct reclaim and memory compaction have failed to allow
+ * the allocation to succeed. The OOM killer is not called with the current
+ * implementation.
+ */
+#define __GFP_IO ((__force gfp_t)___GFP_IO)
+#define __GFP_FS ((__force gfp_t)___GFP_FS)
#define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */
#define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */
+#define __GFP_RECLAIM ((__force gfp_t)(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM))
+#define __GFP_REPEAT ((__force gfp_t)___GFP_REPEAT)
+#define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL)
+#define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY)
/*
- * This may seem redundant, but it's a way of annotating false positives vs.
- * allocations that simply cannot be supported (e.g. page tables).
+ * Action modifiers
+ *
+ * __GFP_COLD indicates that the caller does not expect to be used in the near
+ * future. Where possible, a cache-cold page will be returned.
+ *
+ * __GFP_NOWARN suppresses allocation failure reports.
+ *
+ * __GFP_COMP address compound page metadata.
+ *
+ * __GFP_ZERO returns a zeroed page on success.
+ *
+ * __GFP_NOTRACK avoids tracking with kmemcheck.
+ *
+ * __GFP_NOTRACK_FALSE_POSITIVE is an alias of __GFP_NOTRACK. It's a means of
+ * distinguishing in the source between false positives and allocations that
+ * cannot be supported (e.g. page tables).
+ *
+ * __GFP_OTHER_NODE is for allocations that are on a remote node but that
+ * should not be accounted for as a remote allocation in vmstat. A
+ * typical user would be khugepaged collapsing a huge page on a remote
+ * node.
*/
+#define __GFP_COLD ((__force gfp_t)___GFP_COLD)
+#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN)
+#define __GFP_COMP ((__force gfp_t)___GFP_COMP)
+#define __GFP_ZERO ((__force gfp_t)___GFP_ZERO)
+#define __GFP_NOTRACK ((__force gfp_t)___GFP_NOTRACK)
#define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK)
+#define __GFP_OTHER_NODE ((__force gfp_t)___GFP_OTHER_NODE)
-#define __GFP_BITS_SHIFT 26 /* Room for N __GFP_FOO bits */
+/* Room for N __GFP_FOO bits */
+#define __GFP_BITS_SHIFT 26
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
/*
- * GFP_ATOMIC callers can not sleep, need the allocation to succeed.
- * A lower watermark is applied to allow access to "atomic reserves"
+ * Useful GFP flag combinations that are commonly used. It is recommended
+ * that subsystems start with one of these combinations and then set/clear
+ * __GFP_FOO flags as necessary.
+ *
+ * GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower
+ * watermark is applied to allow access to "atomic reserves"
+ *
+ * GFP_KERNEL is typical for kernel-internal allocations. The caller requires
+ * ZONE_NORMAL or a lower zone for direct access but can direct reclaim.
+ *
+ * GFP_NOWAIT is for kernel allocations that should not stall for direct
+ * reclaim, start physical IO or use any filesystem callback.
+ *
+ * GFP_NOIO will use direct reclaim to discard clean pages or slab pages
+ * that do not require the starting of any physical IO.
+ *
+ * GFP_NOFS will use direct reclaim but will not use any filesystem interfaces.
+ *
+ * GFP_USER is for userspace allocations that also need to be directly
+ * accessibly by the kernel or hardware. It is typically used by hardware
+ * for buffers that are mapped to userspace (e.g. graphics) that hardware
+ * still must DMA to. cpuset limits are enforced for these allocations.
+ *
+ * GFP_DMA exists for historical reasons and should be avoided where possible.
+ * The flags indicates that the caller requires that the lowest zone be
+ * used (ZONE_DMA or 16M on x86-64). Ideally, this would be removed but
+ * it would require careful auditing as some users really require it and
+ * others use the flag to avoid lowmem reserves in ZONE_DMA and treat the
+ * lowest zone as a type of emergency reserve.
+ *
+ * GFP_DMA32 is similar to GFP_DMA except that the caller requires a 32-bit
+ * address.
+ *
+ * GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,
+ * do not need to be directly accessible by the kernel but that cannot
+ * move once in use. An example may be a hardware allocation that maps
+ * data directly into userspace but has no addressing limitations.
+ *
+ * GFP_HIGHUSER_MOVABLE is for userspace allocations that the kernel does not
+ * need direct access to but can use kmap() when access is required. They
+ * are expected to be movable via page reclaim or page migration. Typically,
+ * pages on the LRU would also be allocated with GFP_HIGHUSER_MOVABLE.
+ *
+ * GFP_TRANSHUGE is used for THP allocations. They are compound allocations
+ * that will fail quickly if memory is not available and will not wake
+ * kswapd on failure.
*/
#define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM)
+#define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS)
#define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM)
#define GFP_NOIO (__GFP_RECLAIM)
#define GFP_NOFS (__GFP_RECLAIM | __GFP_IO)
-#define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS)
#define GFP_TEMPORARY (__GFP_RECLAIM | __GFP_IO | __GFP_FS | \
__GFP_RECLAIMABLE)
#define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
+#define GFP_DMA __GFP_DMA
+#define GFP_DMA32 __GFP_DMA32
#define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM)
#define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE)
#define GFP_TRANSHUGE ((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \
__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN) & \
~__GFP_KSWAPD_RECLAIM)
-/* This mask makes up all the page movable related flags */
+/* Convert GFP flags to their corresponding migrate type */
#define GFP_MOVABLE_MASK (__GFP_RECLAIMABLE|__GFP_MOVABLE)
#define GFP_MOVABLE_SHIFT 3
-/* Control page allocator reclaim behavior */
-#define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\
- __GFP_NOWARN|__GFP_REPEAT|__GFP_NOFAIL|\
- __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC)
-
-/* Control slab gfp mask during early boot */
-#define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS))
-
-/* Control allocation constraints */
-#define GFP_CONSTRAINT_MASK (__GFP_HARDWALL|__GFP_THISNODE)
-
-/* Do not use these with a slab allocator */
-#define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
-
-/* Flag - indicates that the buffer will be suitable for DMA. Ignored on some
- platforms, used as appropriate on others */
-
-#define GFP_DMA __GFP_DMA
-
-/* 4GB DMA on some platforms */
-#define GFP_DMA32 __GFP_DMA32
-
-/* Convert GFP flags to their corresponding migrate type */
static inline int gfpflags_to_migratetype(const gfp_t gfp_flags)
{
VM_WARN_ON((gfp_flags & GFP_MOVABLE_MASK) == GFP_MOVABLE_MASK);
/* Group based on mobility */
return (gfp_flags & GFP_MOVABLE_MASK) >> GFP_MOVABLE_SHIFT;
}
+#undef GFP_MOVABLE_MASK
+#undef GFP_MOVABLE_SHIFT
static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
{
projects / openwrt / staging / blogic.git / commitdiff