linux-stable.git/include/linux/gfp_types.h, branch v6.12.85

mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner

2024-09-09T23:39:03+00:00

Three points for this change:

1. We should consolidate all warnings in one place. Currently, the
   order > 1 warning is in the hotpath, while others are in less
   likely scenarios. Moving all warnings to the slowpath will reduce
   the overhead for order > 1 and increase the visibility of other
   warnings.

2. We currently have two warnings for order: one for order > 1 in
   the hotpath and another for order > costly_order in the laziest
   path. I suggest standardizing on order > 1 since it's been in
   use for a long time.

3. We don't need to check for __GFP_NOWARN in this case. __GFP_NOWARN
   is meant to suppress allocation failure reports, but here we're
   dealing with bug detection, not allocation failures. So replace
   WARN_ON_ONCE_GFP by WARN_ON_ONCE.

[v-songbaohua@oppo.com: also update the doc for __GFP_NOFAIL with order > 1]
  Link: https://lkml.kernel.org/r/20240903223935.1697-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240830202823.21478-4-21cnbao@gmail.com
Signed-off-by: Barry Song 
Suggested-by: Vlastimil Babka 
Reviewed-by: Vlastimil Babka 
Acked-by: David Hildenbrand 
Acked-by: Michal Hocko 
Cc: Christoph Hellwig 
Cc: Christoph Lameter 
Cc: Davidlohr Bueso 
Cc: David Rientjes 
Cc: "Eugenio Pérez" 
Cc: Hailong.Liu 
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Jason Wang 
Cc: Joonsoo Kim 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Lorenzo Stoakes 
Cc: Maxime Coquelin 
Cc: "Michael S. Tsirkin" 
Cc: Pekka Enberg 
Cc: Roman Gushchin 
Cc: Uladzislau Rezki (Sony) 
Cc: Xie Yongji 
Cc: Xuan Zhuo 
Cc: Yafang Shao 
Signed-off-by: Andrew Morton

mm: document __GFP_NOFAIL must be blockable

2024-09-09T23:39:03+00:00

Non-blocking allocation with __GFP_NOFAIL is not supported and may still
result in NULL pointers (if we don't return NULL, we result in busy-loop
within non-sleepable contexts):

static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
						struct alloc_context *ac)
{
	...
	/*
	 * Make sure that __GFP_NOFAIL request doesn't leak out and make sure
	 * we always retry
	 */
	if (gfp_mask & __GFP_NOFAIL) {
		/*
		 * All existing users of the __GFP_NOFAIL are blockable, so warn
		 * of any new users that actually require GFP_NOWAIT
		 */
		if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
			goto fail;
		...
	}
	...
fail:
	warn_alloc(gfp_mask, ac->nodemask,
			"page allocation failure: order:%u", order);
got_pg:
	return page;
}

Highlight this in the documentation of __GFP_NOFAIL so that non-mm
subsystems can reject any illegal usage of __GFP_NOFAIL with GFP_ATOMIC,
GFP_NOWAIT, etc.

Link: https://lkml.kernel.org/r/20240830202823.21478-3-21cnbao@gmail.com
Signed-off-by: Barry Song 
Acked-by: Michal Hocko 
Reviewed-by: Christoph Hellwig 
Acked-by: Vlastimil Babka 
Acked-by: Davidlohr Bueso 
Acked-by: David Hildenbrand 
Cc: Christoph Lameter 
Cc: David Rientjes 
Cc: "Eugenio Pérez" 
Cc: Hailong.Liu 
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Jason Wang 
Cc: Joonsoo Kim 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Lorenzo Stoakes 
Cc: Maxime Coquelin 
Cc: "Michael S. Tsirkin" 
Cc: Pekka Enberg 
Cc: Roman Gushchin 
Cc: Uladzislau Rezki (Sony) 
Cc: Xuan Zhuo 
Cc: Christoph Hellwig 
Cc: Xie Yongji 
Cc: Yafang Shao 
Signed-off-by: Andrew Morton

mm: introduce __GFP_NO_OBJ_EXT flag to selectively prevent slabobj_ext creation

2024-04-26T03:55:51+00:00

Introduce __GFP_NO_OBJ_EXT flag in order to prevent recursive allocations
when allocating slabobj_ext on a slab.

Link: https://lkml.kernel.org/r/20240321163705.3067592-8-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Reviewed-by: Kees Cook 
Reviewed-by: Pasha Tatashin 
Reviewed-by: Vlastimil Babka 
Tested-by: Kees Cook 
Cc: Alexander Viro 
Cc: Alex Gaynor 
Cc: Alice Ryhl 
Cc: Andreas Hindborg 
Cc: Benno Lossin 
Cc: "Björn Roy Baron" 
Cc: Boqun Feng 
Cc: Christoph Lameter 
Cc: Dennis Zhou 
Cc: Gary Guo 
Cc: Kent Overstreet 
Cc: Miguel Ojeda 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Cc: Wedson Almeida Filho 
Signed-off-by: Andrew Morton

memblock tests: fix undefined reference to `BIT'

2024-04-04T08:08:33+00:00

commit 772dd0342727 ("mm: enumerate all gfp flags") define gfp flags
with the help of BIT, while gfp_types.h doesn't include header file for
the definition. This through an error on building memblock tests.

Let's include linux/bits.h to fix it.

Signed-off-by: Wei Yang 
CC: Suren Baghdasaryan 
CC: Michal Hocko 
Link: https://lore.kernel.org/r/20240402132701.29744-4-richard.weiyang@gmail.com
Signed-off-by: Mike Rapoport (IBM)

mm: enumerate all gfp flags

2024-03-05T01:01:18+00:00

Introduce GFP bits enumeration to let compiler track the number of used
bits (which depends on the config options) instead of hardcoding them. 
That simplifies __GFP_BITS_SHIFT calculation.

Link: https://lkml.kernel.org/r/20240224015800.2569851-1-surenb@google.com
Suggested-by: Petr Tesařík 
Signed-off-by: Suren Baghdasaryan 
Reviewed-by: Kees Cook 
Reviewed-by: Pasha Tatashin 
Acked-by: Michal Hocko 
Cc: Kent Overstreet 
Cc: Petr Tesarik 
Signed-off-by: Andrew Morton

gfp: gfp_types.h: fix typos & punctuation

2023-12-20T22:48:14+00:00

Correct typos/spellos and punctutation.

Link: https://lkml.kernel.org/r/20231213043316.10128-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap 
Signed-off-by: Andrew Morton

gfp: include __GFP_NOWARN in GFP_NOWAIT

2023-12-11T00:51:39+00:00

GFP_NOWAIT callers are always prepared for their allocations to fail
because they fail so frequently.  Forcing the callers to remember to add
__GFP_NOWARN is just annoying and leads to an endless stream of patches
for the places where we forgot to add it.

We can now remove __GFP_NOWARN from all the callers which specify
GFP_NOWAIT, but I'd rather wait a cycle and send patches to each
maintainer instead of creating a big pile of merge conflicts.

Link: https://lkml.kernel.org/r/20231109211507.2262419-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

kasan: remove PG_skip_kasan_poison flag

2023-03-28T23:20:16+00:00

Code inspection reveals that PG_skip_kasan_poison is redundant with
kasantag, because the former is intended to be set iff the latter is the
match-all tag.  It can also be observed that it's basically pointless to
poison pages which have kasantag=0, because any pages with this tag would
have been pointed to by pointers with match-all tags, so poisoning the
pages would have little to no effect in terms of bug detection. 
Therefore, change the condition in should_skip_kasan_poison() to check
kasantag instead, and remove PG_skip_kasan_poison and associated flags.

Link: https://lkml.kernel.org/r/20230310042914.3805818-3-pcc@google.com
Link: https://linux-review.googlesource.com/id/I57f825f2eaeaf7e8389d6cf4597c8a5821359838
Signed-off-by: Peter Collingbourne 
Reviewed-by: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Catalin Marinas 
Cc: Evgenii Stepanov 
Cc: Vincenzo Frascino 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

mm: discard __GFP_ATOMIC

2023-02-03T06:33:13+00:00

__GFP_ATOMIC serves little purpose.  Its main effect is to set
ALLOC_HARDER which adds a few little boosts to increase the chance of an
allocation succeeding, one of which is to lower the water-mark at which it
will succeed.

It is *always* paired with __GFP_HIGH which sets ALLOC_HIGH which also
adjusts this watermark.  It is probable that other users of __GFP_HIGH
should benefit from the other little bonuses that __GFP_ATOMIC gets.

__GFP_ATOMIC also gives a warning if used with __GFP_DIRECT_RECLAIM.
There is little point to this.  We already get a might_sleep() warning if
__GFP_DIRECT_RECLAIM is set.

__GFP_ATOMIC allows the "watermark_boost" to be side-stepped.  It is
probable that testing ALLOC_HARDER is a better fit here.

__GFP_ATOMIC is used by tegra-smmu.c to check if the allocation might
sleep.  This should test __GFP_DIRECT_RECLAIM instead.

This patch:
 - removes __GFP_ATOMIC
 - allows __GFP_HIGH allocations to ignore watermark boosting as well
   as GFP_ATOMIC requests.
 - makes other adjustments as suggested by the above.

The net result is not change to GFP_ATOMIC allocations.  Other
allocations that use __GFP_HIGH will benefit from a few different extra
privileges.  This affects:
  xen, dm, md, ntfs3
  the vermillion frame buffer
  hibernation
  ksm
  swap
all of which likely produce more benefit than cost if these selected
allocation are more likely to succeed quickly.

[mgorman: Minor adjustments to rework on top of a series]
Link: https://lkml.kernel.org/r/163712397076.13692.4727608274002939094@noble.neil.brown.name
Link: https://lkml.kernel.org/r/20230113111217.14134-7-mgorman@techsingularity.net
Signed-off-by: NeilBrown 
Signed-off-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Acked-by: Michal Hocko 
Cc: Matthew Wilcox 
Cc: Thierry Reding 
Signed-off-by: Andrew Morton

Merge tag 'bitmap-6.0-rc1' of https://github.com/norov/linux

2022-08-08T00:52:35+00:00

Pull bitmap updates from Yury Norov:

 - fix the duplicated comments on bitmap_to_arr64() (Qu Wenruo)

 - optimize out non-atomic bitops on compile-time constants (Alexander
   Lobakin)

 - cleanup bitmap-related headers (Yury Norov)

 - x86/olpc: fix 'logical not is only applied to the left hand side'
   (Alexander Lobakin)

 - lib/nodemask: inline wrappers around bitmap (Yury Norov)

* tag 'bitmap-6.0-rc1' of https://github.com/norov/linux: (26 commits)
  lib/nodemask: inline next_node_in() and node_random()
  powerpc: drop dependency on  in archrandom.h
  x86/olpc: fix 'logical not is only applied to the left hand side'
  lib/cpumask: move some one-line wrappers to header file
  headers/deps: mm: align MANITAINERS and Docs with new gfp.h structure
  headers/deps: mm: Split  out of 
  headers/deps: mm: Optimize  header dependencies
  lib/cpumask: move trivial wrappers around find_bit to the header
  lib/cpumask: change return types to unsigned where appropriate
  cpumask: change return types to bool where appropriate
  lib/bitmap: change type of bitmap_weight to unsigned long
  lib/bitmap: change return types to bool where appropriate
  arm: align find_bit declarations with generic kernel
  iommu/vt-d: avoid invalid memory access via node_online(NUMA_NO_NODE)
  lib/test_bitmap: test the tail after bitmap_to_arr64()
  lib/bitmap: fix off-by-one in bitmap_to_arr64()
  lib: test_bitmap: add compile-time optimization/evaluations assertions
  bitmap: don't assume compiler evaluates small mem*() builtins calls
  net/ice: fix initializing the bitmap in the switch code
  bitops: let optimize out non-atomic bitops on compile-time constants
  ...