[PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context

[PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context

[Vlastimil Babka (SUSE)]

This series is based on slab/for-next. If all goes well, it would
hopefully go to slab/for-next soon after the 7.2 merge window, so any
other work can be based on it to avoid conflicts, as it touches a lot
parts of slab.

Git: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slab_alloc_flags

The slab implementation currently relies on gfp flags to convey
some context information internally:

- The absence of both __GFP_RECLAIM flags is interpreted as "cannot spin
  on locks", and intended to be used by kmalloc_nolock(). But false
  positives are possible e.g. during early boot where gfp_allowed_mask
  clears __GFP_RECLAIM from all allocations. This leads to unnecessary
  allocation failures and workarounds such as fd3634312a04 ("debugobject:
  Make it work with deferred page initialization - again").

- __GFP_NO_OBJ_EXT exists and takes up valuable bit in the gfp flags
  space, only to prevent recursive kmalloc() allocations for obj_ext
  arrays and sheaves.

The page allocator uses its internal alloc_flags to convey various
context information, including ALLOC_TRYLOCK (meaning "cannot spin").
This series copies that concept for the slab allocator, with its own
slab-specific internal flags:

- SLAB_ALLOC_DEFAULT - no extra flags (the value is 0), but explicit
- SLAB_ALLOC_TRYLOCK - do not spin on locks (used by kmalloc_nolock())
- SLAB_ALLOC_NEW_SLAB - replacing existing 'bool new_slab' parameter
			for allocating obj_ext arrays
- SLAB_ALLOC_NO_RECURSE - replacing usage of __GFP_NO_OBJ_EXT

To reduce the amount of parameters in various internal functions, we
additionally introduce slab_alloc_context (also inspired by page
allocator's alloc_context) for passing a number of existing arguments
and the new alloc_flags:

/* Structure holding extra parameters for slab allocations */
struct slab_alloc_context {
	unsigned long caller_addr;
	unsigned long orig_size;
	unsigned int alloc_flags;
	struct list_lru *lru;
};

This also replaces the existing struct partial_context.

The last necessary piece is kmalloc_flags() which can take the
alloc_flags in addition to gfp flags and is intended for the recursive
allocations of sheaves and obj_ext arrays, so that both
SLAB_ALLOC_TRYLOCK and SLAB_ALLOC_NO_RECURSE can be communicated.
Internally it decides between kmalloc_nolock() and normal kmalloc()
depending SLAB_ALLOC_TRYLOCK.

The rest of the series is gradually expanding the usage of both
alloc_flags and slab_alloc_context as necessary, with bits of
refactoring. Then, __GFP_NO_OBJ_EXT is removed completely.

Note that some usage of gfpflags_allow_spinning() relying on absence of
__GFP_RECLAIM remains outside of slab (and page allocator) in memcg,
page_owner and stackdepot code. These can thus yield false-positive
decisions that spinning is not allowed, but should not result in
important allocations failing anymore.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
Vlastimil Babka (SUSE) (15):
      mm/slab: always zero only requested size on alloc
      mm/slab: stop inlining __slab_alloc_node()
      mm/slab: introduce slab_alloc_context
      mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK
      mm/slab: add alloc_flags to slab_alloc_context
      mm/slab: replace struct partial_context with slab_alloc_context
      mm/slab: pass alloc_flags to new slab allocation
      mm/slab: pass alloc_flags through slab_post_alloc_hook() chain
      mm/slab: replace slab_alloc_node() parameters with slab_alloc_context
      mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags
      mm/slab: pass slab_alloc_context to __do_kmalloc_node()
      mm/slab: introduce kmalloc_flags()
      mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts()
      mm/slab: replace __GFP_NO_OBJ_EXT with SLAB_ALLOC_NO_RECURSE for sheaves
      mm: remove the __GFP_NO_OBJ_EXT flag

 include/linux/gfp_types.h       |   7 -
 include/linux/slab.h            |  14 +-
 include/trace/events/mmflags.h  |  10 +-
 lib/alloc_tag.c                 |   2 +-
 mm/kfence/core.c                |   6 +-
 mm/memcontrol.c                 |   5 +-
 mm/slab.h                       |  16 +-
 mm/slub.c                       | 423 ++++++++++++++++++++++++----------------
 tools/include/linux/gfp_types.h |   7 -
 9 files changed, 288 insertions(+), 202 deletions(-)
---
base-commit: 500b2c9755301742bdbb61249511ac11a4665dae
change-id: 20260601-slab_alloc_flags-25c782b0c57c

Best regards,
--  
Vlastimil Babka (SUSE) <vbabka@kernel.org>

[PATCH RFC 01/15] mm/slab: always zero only requested size on alloc

[Vlastimil Babka (SUSE)]

When zeroing on alloc is requested (by __GFP_ZERO or the init_on_alloc
parameter), we have been trying to zero the whole kmalloc bucket size
and not just requested size, if possible.

This probably comes from the past where ksize() could be used to
discover the bucket size and use it opportunistically beyond the
requested size. This is now forbidden and enabling debugging such as
KASAN or slab's red zoning would catch this misuse. Therefore, nobody
can be relying on __GFP_ZERO zeroing beyond requested size.

Theoretically it might still improve hardening in case of unintended
accesses beond requested size accessing some sensitive data from a
previous allocation. But then, init_on_free is probably used also for
hardening and would have cleared that.

So the usefullness of zeroing beyond requested size is practically none
nowadays. The disadvantages for doing it are:

- Interaction with KFENCE, which perfoms the zeroing on its own because
  it has its own redzone beyond requested size. As a consequence
  slab_post_alloc_hook() has an 'init' parameter which has to be
  evaluated in all callers (via slab_want_init_on_alloc()).

  For kfence allocations in slab_alloc_node() this evaluation is subtly
  skipped over in order to do the right thing. Other callers (i.e.
  kmem_cache_alloc_bulk_noprof()) evaluate it unconditionally even if
  they do end up with a kfence allocation. This is only subtly not a
  problem, as those are not kmalloc allocations and are using
  s->object_size as requested size, so it doesn't interfere with kfence's
  redzone. There's just a unnecessary double zeroing (in both kfence and
  slab_post_alloc_hook()), but it's all very fragile and contradicts the
  comment in kfence_guarded_alloc().

- Interaction with slab's redzoning where we have to limit the zeroing
  to requested size.

We can make the code much more simple by always zeroing only up to the
requested size. Move slab_want_init_on_alloc() call to
slab_post_alloc_hook(), removing the parameter. Remove the red zone
handling.

For kfence's zeroing code, update the comment. We could remove it
completely, but due to possible interactions with KASAN, there are
configurations where neither slab or KASAN would zero the object,
so simply do it in kfence. At worst the zeroing will happen twice, but
kfence allocations are rare by design so the cost is negligible.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/kfence/core.c |  6 +++---
 mm/slub.c        | 35 +++++++----------------------------
 2 files changed, 10 insertions(+), 31 deletions(-)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 655dc5ce3240..c765ba0a3a67 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -499,9 +499,9 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
 	set_canary(meta);
 
 	/*
-	 * We check slab_want_init_on_alloc() ourselves, rather than letting
-	 * SL*B do the initialization, as otherwise we might overwrite KFENCE's
-	 * redzone.
+	 * SLUB will generally init kfence objects, but due to possible
+	 * interactions with KASAN, it might not happen, so do it ourselves.
+	 * In the worst case the init just happens twice.
 	 */
 	if (unlikely(slab_want_init_on_alloc(gfp, cache)))
 		memzero_explicit(addr, size);
diff --git a/mm/slub.c b/mm/slub.c
index 63c1ef998dd3..f787dc422d1b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4565,26 +4565,14 @@ struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
 
 static __fastpath_inline
 bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
-			  gfp_t flags, size_t size, void **p, bool init,
+			  gfp_t flags, size_t size, void **p,
 			  unsigned int orig_size)
 {
-	unsigned int zero_size = s->object_size;
+	bool init = slab_want_init_on_alloc(flags, s);
 	bool kasan_init = init;
 	size_t i;
 	gfp_t init_flags = flags & gfp_allowed_mask;
 
-	/*
-	 * For kmalloc object, the allocated memory size(object_size) is likely
-	 * larger than the requested size(orig_size). If redzone check is
-	 * enabled for the extra space, don't zero it, as it will be redzoned
-	 * soon. The redzone operation for this extra space could be seen as a
-	 * replacement of current poisoning under certain debug option, and
-	 * won't break other sanity checks.
-	 */
-	if (kmem_cache_debug_flags(s, SLAB_STORE_USER | SLAB_RED_ZONE) &&
-	    (s->flags & SLAB_KMALLOC))
-		zero_size = orig_size;
-
 	/*
 	 * When slab_debug is enabled, avoid memory initialization integrated
 	 * into KASAN and instead zero out the memory via the memset below with
@@ -4607,7 +4595,7 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 		p[i] = kasan_slab_alloc(s, p[i], init_flags, kasan_init);
 		if (p[i] && init && (!kasan_init ||
 				     !kasan_has_integrated_init()))
-			memset(p[i], 0, zero_size);
+			memset(p[i], 0, orig_size);
 		if (gfpflags_allow_spinning(flags))
 			kmemleak_alloc_recursive(p[i], s->object_size, 1,
 						 s->flags, init_flags);
@@ -4908,7 +4896,6 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 		gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
 {
 	void *object;
-	bool init = false;
 
 	s = slab_pre_alloc_hook(s, gfpflags);
 	if (unlikely(!s))
@@ -4924,16 +4911,13 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 		object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
 
 	maybe_wipe_obj_freeptr(s, object);
-	init = slab_want_init_on_alloc(gfpflags, s);
 
 out:
 	/*
-	 * When init equals 'true', like for kzalloc() family, only
-	 * @orig_size bytes might be zeroed instead of s->object_size
 	 * In case this fails due to memcg_slab_post_alloc_hook(),
 	 * object is set to NULL
 	 */
-	slab_post_alloc_hook(s, lru, gfpflags, 1, &object, init, orig_size);
+	slab_post_alloc_hook(s, lru, gfpflags, 1, &object, orig_size);
 
 	return object;
 }
@@ -5228,7 +5212,6 @@ kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp,
 				   struct slab_sheaf *sheaf)
 {
 	void *ret = NULL;
-	bool init;
 
 	if (sheaf->size == 0)
 		goto out;
@@ -5238,10 +5221,8 @@ kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp,
 	if (likely(!ret))
 		ret = sheaf->objects[--sheaf->size];
 
-	init = slab_want_init_on_alloc(gfp, s);
-
 	/* add __GFP_NOFAIL to force successful memcg charging */
-	slab_post_alloc_hook(s, NULL, gfp | __GFP_NOFAIL, 1, &ret, init, s->object_size);
+	slab_post_alloc_hook(s, NULL, gfp | __GFP_NOFAIL, 1, &ret, s->object_size);
 out:
 	trace_kmem_cache_alloc(_RET_IP_, ret, s, gfp, NUMA_NO_NODE);
 
@@ -5421,8 +5402,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 
 success:
 	maybe_wipe_obj_freeptr(s, ret);
-	slab_post_alloc_hook(s, NULL, alloc_gfp, 1, &ret,
-			     slab_want_init_on_alloc(alloc_gfp, s), orig_size);
+	slab_post_alloc_hook(s, NULL, alloc_gfp, 1, &ret, orig_size);
 
 	ret = kasan_kmalloc(s, ret, orig_size, alloc_gfp);
 	return ret;
@@ -7337,8 +7317,7 @@ bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,
 
 out:
 	/* memcg and kmem_cache debug support and memory initialization */
-	return likely(slab_post_alloc_hook(s, NULL, flags, size, p,
-			slab_want_init_on_alloc(flags, s), s->object_size));
+	return likely(slab_post_alloc_hook(s, NULL, flags, size, p, s->object_size));
 }
 EXPORT_SYMBOL(kmem_cache_alloc_bulk_noprof);
 

-- 
2.54.0

[PATCH RFC 02/15] mm/slab: stop inlining __slab_alloc_node()

[Vlastimil Babka (SUSE)]

With sheaves, this is no longer part of the allocation fastpath.  For
the same reason, also mark the call to it from slab_alloc_node() as
unlikely().

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index f787dc422d1b..af85f338db4f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4519,8 +4519,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	return object;
 }
 
-static __always_inline void *__slab_alloc_node(struct kmem_cache *s,
-		gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
+static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node,
+			       unsigned long addr, size_t orig_size)
 {
 	void *object;
 
@@ -4907,7 +4907,7 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 
 	object = alloc_from_pcs(s, gfpflags, node);
 
-	if (!object)
+	if (unlikely(!object))
 		object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
 
 	maybe_wipe_obj_freeptr(s, object);

-- 
2.54.0

[PATCH RFC 03/15] mm/slab: introduce slab_alloc_context

[Vlastimil Babka (SUSE)]

Similarly to page allocator's struct alloc_context, introduce a helper
struct to hold a part of the allocation arguments. This will allow
reducing the number of parameters in many functions of the
implementation, and extend them easily if needed.

For now, make it hold the caller address and the originally requested
allocation size.

Convert alloc_single_from_new_slab(), __slab_alloc_node() and
___slab_alloc(). No functional change intended.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 46 +++++++++++++++++++++++++++++++++-------------
 1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index af85f338db4f..06fc1656080f 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -213,6 +213,12 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
 static DEFINE_STATIC_KEY_FALSE(strict_numa);
 #endif
 
+/* Structure holding extra parameters for slab allocations */
+struct slab_alloc_context {
+	unsigned long caller_addr;
+	unsigned long orig_size;
+};
+
 /* Structure holding parameters for get_from_partial() call chain */
 struct partial_context {
 	gfp_t flags;
@@ -3687,7 +3693,8 @@ static inline void init_slab_obj_iter(struct kmem_cache *s, struct slab *slab,
  * and put the slab to the partial (or full) list.
  */
 static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
-					int orig_size, bool allow_spin)
+					struct slab_alloc_context *ac,
+					bool allow_spin)
 {
 	struct kmem_cache_node *n;
 	struct slab_obj_iter iter;
@@ -3705,7 +3712,7 @@ static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
 	/* alloc_debug_processing() always expects a valid freepointer */
 	set_freepointer(s, object, slab->freelist);
 
-	if (!alloc_debug_processing(s, slab, object, orig_size)) {
+	if (!alloc_debug_processing(s, slab, object, ac->orig_size)) {
 		/*
 		 * It's not really expected that this would fail on a
 		 * freshly allocated slab, but a concurrent memory
@@ -4443,7 +4450,7 @@ static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab,
  * slab.
  */
 static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
-			   unsigned long addr, unsigned int orig_size)
+			   struct slab_alloc_context *ac)
 {
 	bool allow_spin = gfpflags_allow_spinning(gfpflags);
 	void *object;
@@ -4476,7 +4483,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 			pc.flags = GFP_NOWAIT | __GFP_THISNODE;
 	}
 
-	pc.orig_size = orig_size;
+	pc.orig_size = ac->orig_size;
 	object = get_from_partial(s, node, &pc);
 	if (object)
 		goto success;
@@ -4496,7 +4503,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	stat(s, ALLOC_SLAB);
 
 	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
-		object = alloc_single_from_new_slab(s, slab, orig_size, allow_spin);
+		object = alloc_single_from_new_slab(s, slab, ac, allow_spin);
 
 		if (likely(object))
 			goto success;
@@ -4514,13 +4521,13 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 
 success:
 	if (kmem_cache_debug_flags(s, SLAB_STORE_USER))
-		set_track(s, object, TRACK_ALLOC, addr, gfpflags);
+		set_track(s, object, TRACK_ALLOC, ac->caller_addr, gfpflags);
 
 	return object;
 }
 
 static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node,
-			       unsigned long addr, size_t orig_size)
+			       struct slab_alloc_context *ac)
 {
 	void *object;
 
@@ -4545,7 +4552,7 @@ static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node,
 	}
 #endif
 
-	object = ___slab_alloc(s, gfpflags, node, addr, orig_size);
+	object = ___slab_alloc(s, gfpflags, node, ac);
 
 	return object;
 }
@@ -4907,8 +4914,13 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 
 	object = alloc_from_pcs(s, gfpflags, node);
 
-	if (unlikely(!object))
-		object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
+	if (unlikely(!object)) {
+		struct slab_alloc_context ac = {
+			.caller_addr = addr,
+			.orig_size = orig_size,
+		};
+		object = __slab_alloc_node(s, gfpflags, node, &ac);
+	}
 
 	maybe_wipe_obj_freeptr(s, object);
 
@@ -5373,13 +5385,18 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 	if (ret)
 		goto success;
 
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = orig_size,
+	};
+
 	/*
 	 * Do not call slab_alloc_node(), since trylock mode isn't
 	 * compatible with slab_pre_alloc_hook/should_failslab and
 	 * kfence_alloc. Hence call __slab_alloc_node() (at most twice)
 	 * and slab_post_alloc_hook() directly.
 	 */
-	ret = __slab_alloc_node(s, alloc_gfp, node, _RET_IP_, orig_size);
+	ret = __slab_alloc_node(s, alloc_gfp, node, &ac);
 
 	/*
 	 * It's possible we failed due to trylock as we preempted someone with
@@ -7221,10 +7238,13 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
 	int i;
 
 	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
+		struct slab_alloc_context ac = {
+			.caller_addr = _RET_IP_,
+			.orig_size = s->object_size,
+		};
 		for (i = 0; i < size; i++) {
 
-			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE, _RET_IP_,
-					     s->object_size);
+			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE, &ac);
 			if (unlikely(!p[i]))
 				goto error;
 

-- 
2.54.0

[PATCH RFC 04/15] mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK

[Vlastimil Babka (SUSE)]

Similarly to the page allocators, introduce slab-allocator specific
alloc flags that internally control allocation behavior in addition to
gfp_flags, without occupying the limited gfp flags space.

Introduce the first flag SLAB_ALLOC_TRYLOCK that behaves similarly to
page allocator's ALLOC_TRYLOCK and will be used to reimplement
kmalloc_nolock()'s "!allow_spin" behavior. That currently relies on
gfpflags_allow_spinning() and thus the lack of both __GFP_RECLAIM flags,
importantly __GFP_KSWAPD_RECLAIM. This can give false-positive results
e.g. in early boot with a restricted gfp_allowed_mask.

Also introduce alloc_flags_allow_spinning() to replace the usage of
gfpflags_allow_spinning().

Start using alloc_flags and the new check first in alloc_from_pcs() and
__pcs_replace_empty_main(). This means some slab allocations that were
falsely treated as kmalloc_nolock() due to their gfp flags will now have
higher chances of succeed, and this will further increase with followup
changes.

Remove a WARN_ON_ONCE() from refill_objects() as it's now legitimate to
reach it from a slab allocation that's not _nolock() and yet lacks
__GFP_KSWAPD_RECLAIM for other reasons.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slab.h |  9 +++++++++
 mm/slub.c | 17 ++++++++---------
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 1bf9c3021ae3..3e75182ee144 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -16,6 +16,15 @@
  * Internal slab definitions
  */
 
+/* slab's alloc_flags definitions */
+#define SLAB_ALLOC_DEFAULT	0x00
+#define SLAB_ALLOC_TRYLOCK	0x01
+
+static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags)
+{
+	return !(alloc_flags & SLAB_ALLOC_TRYLOCK);
+}
+
 #ifdef CONFIG_64BIT
 # ifdef system_has_cmpxchg128
 # define system_has_freelist_aba()	system_has_cmpxchg128()
diff --git a/mm/slub.c b/mm/slub.c
index 06fc1656080f..278d8cbcc7ee 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4622,7 +4622,8 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
  * unlocked.
  */
 static struct slub_percpu_sheaves *
-__pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, gfp_t gfp)
+__pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,
+			 gfp_t gfp, unsigned int alloc_flags)
 {
 	struct slab_sheaf *empty = NULL;
 	struct slab_sheaf *full;
@@ -4648,7 +4649,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,
 		return NULL;
 	}
 
-	allow_spin = gfpflags_allow_spinning(gfp);
+	allow_spin = alloc_flags_allow_spinning(alloc_flags);
 
 	full = barn_replace_empty_sheaf(barn, pcs->main, allow_spin);
 
@@ -4734,7 +4735,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,
 }
 
 static __fastpath_inline
-void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node)
+void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, unsigned int alloc_flags, int node)
 {
 	struct slub_percpu_sheaves *pcs;
 	bool node_requested;
@@ -4779,7 +4780,7 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node)
 	pcs = this_cpu_ptr(s->cpu_sheaves);
 
 	if (unlikely(pcs->main->size == 0)) {
-		pcs = __pcs_replace_empty_main(s, pcs, gfp);
+		pcs = __pcs_replace_empty_main(s, pcs, gfp, alloc_flags);
 		if (unlikely(!pcs))
 			return NULL;
 	}
@@ -4912,7 +4913,7 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 	if (unlikely(object))
 		goto out;
 
-	object = alloc_from_pcs(s, gfpflags, node);
+	object = alloc_from_pcs(s, gfpflags, SLAB_ALLOC_DEFAULT, node);
 
 	if (unlikely(!object)) {
 		struct slab_alloc_context ac = {
@@ -5343,6 +5344,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 {
 	gfp_t alloc_gfp = __GFP_NOWARN | __GFP_NOMEMALLOC | gfp_flags;
 	size_t orig_size = size;
+	unsigned int alloc_flags = SLAB_ALLOC_TRYLOCK;
 	struct kmem_cache *s;
 	bool can_retry = true;
 	void *ret;
@@ -5381,7 +5383,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 		 */
 		return NULL;
 
-	ret = alloc_from_pcs(s, alloc_gfp, node);
+	ret = alloc_from_pcs(s, alloc_gfp, alloc_flags, node);
 	if (ret)
 		goto success;
 
@@ -7200,9 +7202,6 @@ refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,
 	unsigned int refilled;
 	struct slab *slab;
 
-	if (WARN_ON_ONCE(!gfpflags_allow_spinning(gfp)))
-		return 0;
-
 	refilled = __refill_objects_node(s, p, gfp, min, max,
 					 get_node(s, local_node),
 					 /* allow_spin = */ true);

-- 
2.54.0

[PATCH RFC 05/15] mm/slab: add alloc_flags to slab_alloc_context

[Vlastimil Babka (SUSE)]

Add alloc_flags as a new field to the slab_alloc_context helper struct,
so we can pass it to more functions in the slab implementation without
adding another function parameter.

Start checking them via alloc_flags_allow_spinning() in
alloc_single_from_new_slab() (where we can drop the allow_spin
parameter) and ___slab_alloc(). This further reduces false-positive
spinning-not-allowed from allocations that are not kmalloc_nolock() but
lack __GFP_RECLAIM flags.

_kmalloc_nolock_noprof() initializes ac.alloc_flags using its flags that
are SLAB_ALLOC_TRYLOCK. slab_alloc_node() and __kmem_cache_alloc_bulk()
are not reachable from kmalloc_nolock() and all their callers expect
spinning to be allowed, so they can use SLAB_ALLOC_DEFAULT. This is
temporary as the scope of slab_alloc_context will further move to the
callers, making the alloc_flags usage more obvious.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 278d8cbcc7ee..b2a452dd70fa 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -217,6 +217,7 @@ static DEFINE_STATIC_KEY_FALSE(strict_numa);
 struct slab_alloc_context {
 	unsigned long caller_addr;
 	unsigned long orig_size;
+	unsigned int alloc_flags;
 };
 
 /* Structure holding parameters for get_from_partial() call chain */
@@ -3693,9 +3694,9 @@ static inline void init_slab_obj_iter(struct kmem_cache *s, struct slab *slab,
  * and put the slab to the partial (or full) list.
  */
 static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
-					struct slab_alloc_context *ac,
-					bool allow_spin)
+					struct slab_alloc_context *ac)
 {
+	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
 	struct kmem_cache_node *n;
 	struct slab_obj_iter iter;
 	bool needs_add_partial;
@@ -4452,7 +4453,7 @@ static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab,
 static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 			   struct slab_alloc_context *ac)
 {
-	bool allow_spin = gfpflags_allow_spinning(gfpflags);
+	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
 	void *object;
 	struct slab *slab;
 	struct partial_context pc;
@@ -4503,7 +4504,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	stat(s, ALLOC_SLAB);
 
 	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
-		object = alloc_single_from_new_slab(s, slab, ac, allow_spin);
+		object = alloc_single_from_new_slab(s, slab, ac);
 
 		if (likely(object))
 			goto success;
@@ -4903,6 +4904,7 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
 static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list_lru *lru,
 		gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
 {
+	const unsigned int alloc_flags = SLAB_ALLOC_DEFAULT;
 	void *object;
 
 	s = slab_pre_alloc_hook(s, gfpflags);
@@ -4913,12 +4915,13 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 	if (unlikely(object))
 		goto out;
 
-	object = alloc_from_pcs(s, gfpflags, SLAB_ALLOC_DEFAULT, node);
+	object = alloc_from_pcs(s, gfpflags, alloc_flags, node);
 
 	if (unlikely(!object)) {
 		struct slab_alloc_context ac = {
 			.caller_addr = addr,
 			.orig_size = orig_size,
+			.alloc_flags = alloc_flags,
 		};
 		object = __slab_alloc_node(s, gfpflags, node, &ac);
 	}
@@ -5390,6 +5393,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 	struct slab_alloc_context ac = {
 		.caller_addr = _RET_IP_,
 		.orig_size = orig_size,
+		.alloc_flags = alloc_flags,
 	};
 
 	/*
@@ -7240,6 +7244,7 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
 		struct slab_alloc_context ac = {
 			.caller_addr = _RET_IP_,
 			.orig_size = s->object_size,
+			.alloc_flags = SLAB_ALLOC_DEFAULT,
 		};
 		for (i = 0; i < size; i++) {
 

-- 
2.54.0

[PATCH RFC 06/15] mm/slab: replace struct partial_context with slab_alloc_context

[Vlastimil Babka (SUSE)]

Refactor get_from_partial_node(), get_from_any_partial(),
get_from_partial() and ___slab_alloc().

Remove struct partial_context, which used to be more substantial but
shrank as part of the sheaves conversion. Instead pass gfp_flags and
pointer to the new slab_alloc_context, which together is a superset of
partial_context.

This means alloc_flags are now available and we can use them to
determine if spinning is allowed, further reducing false positive "not
allowed" in the slow path due to gfp flags lacking __GFP_RECLAIM.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 52 ++++++++++++++++++++++++----------------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index b2a452dd70fa..0bde4f6d9126 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -220,12 +220,6 @@ struct slab_alloc_context {
 	unsigned int alloc_flags;
 };
 
-/* Structure holding parameters for get_from_partial() call chain */
-struct partial_context {
-	gfp_t flags;
-	unsigned int orig_size;
-};
-
 /* Structure holding parameters for get_partial_node_bulk() */
 struct partial_bulk_context {
 	gfp_t flags;
@@ -3826,7 +3820,8 @@ static bool get_partial_node_bulk(struct kmem_cache *s,
  */
 static void *get_from_partial_node(struct kmem_cache *s,
 				   struct kmem_cache_node *n,
-				   struct partial_context *pc)
+				   gfp_t gfp_flags,
+				   struct slab_alloc_context *ac)
 {
 	struct slab *slab, *slab2;
 	unsigned long flags;
@@ -3841,7 +3836,7 @@ static void *get_from_partial_node(struct kmem_cache *s,
 	if (!n || !n->nr_partial)
 		return NULL;
 
-	if (gfpflags_allow_spinning(pc->flags))
+	if (alloc_flags_allow_spinning(ac->alloc_flags))
 		spin_lock_irqsave(&n->list_lock, flags);
 	else if (!spin_trylock_irqsave(&n->list_lock, flags))
 		return NULL;
@@ -3849,12 +3844,12 @@ static void *get_from_partial_node(struct kmem_cache *s,
 
 		struct freelist_counters old, new;
 
-		if (!pfmemalloc_match(slab, pc->flags))
+		if (!pfmemalloc_match(slab, gfp_flags))
 			continue;
 
 		if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
 			object = alloc_single_from_partial(s, n, slab,
-							pc->orig_size);
+							ac->orig_size);
 			if (object)
 				break;
 			continue;
@@ -3888,15 +3883,16 @@ static void *get_from_partial_node(struct kmem_cache *s,
 /*
  * Get an object from somewhere. Search in increasing NUMA distances.
  */
-static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *pc)
+static void *get_from_any_partial(struct kmem_cache *s, gfp_t gfp_flags,
+				  struct slab_alloc_context *ac)
 {
 #ifdef CONFIG_NUMA
 	struct zonelist *zonelist;
 	struct zoneref *z;
 	struct zone *zone;
-	enum zone_type highest_zoneidx = gfp_zone(pc->flags);
+	enum zone_type highest_zoneidx = gfp_zone(gfp_flags);
 	unsigned int cpuset_mems_cookie;
-	bool allow_spin = gfpflags_allow_spinning(pc->flags);
+	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
 
 	/*
 	 * The defrag ratio allows a configuration of the tradeoffs between
@@ -3930,16 +3926,17 @@ static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *
 		if (allow_spin)
 			cpuset_mems_cookie = read_mems_allowed_begin();
 
-		zonelist = node_zonelist(mempolicy_slab_node(), pc->flags);
+		zonelist = node_zonelist(mempolicy_slab_node(), gfp_flags);
 		for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) {
 			struct kmem_cache_node *n;
 
 			n = get_node(s, zone_to_nid(zone));
 
-			if (n && cpuset_zone_allowed(zone, pc->flags) &&
+			if (n && cpuset_zone_allowed(zone, gfp_flags) &&
 					n->nr_partial > s->min_partial) {
 
-				void *object = get_from_partial_node(s, n, pc);
+				void *object = get_from_partial_node(s, n,
+								gfp_flags, ac);
 
 				if (object) {
 					/*
@@ -3961,8 +3958,8 @@ static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *
 /*
  * Get an object from a partial slab
  */
-static void *get_from_partial(struct kmem_cache *s, int node,
-			      struct partial_context *pc)
+static void *get_from_partial(struct kmem_cache *s, int node, gfp_t flags,
+			      struct slab_alloc_context *ac)
 {
 	int searchnode = node;
 	void *object;
@@ -3970,11 +3967,11 @@ static void *get_from_partial(struct kmem_cache *s, int node,
 	if (node == NUMA_NO_NODE)
 		searchnode = numa_mem_id();
 
-	object = get_from_partial_node(s, get_node(s, searchnode), pc);
-	if (object || (node != NUMA_NO_NODE && (pc->flags & __GFP_THISNODE)))
+	object = get_from_partial_node(s, get_node(s, searchnode), flags, ac);
+	if (object || (node != NUMA_NO_NODE && (flags & __GFP_THISNODE)))
 		return object;
 
-	return get_from_any_partial(s, pc);
+	return get_from_any_partial(s, flags, ac);
 }
 
 static bool has_pcs_used(int cpu, struct kmem_cache *s)
@@ -4454,16 +4451,16 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 			   struct slab_alloc_context *ac)
 {
 	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
+	gfp_t trynode_flags;
 	void *object;
 	struct slab *slab;
-	struct partial_context pc;
 	bool try_thisnode = true;
 
 	stat(s, ALLOC_SLOWPATH);
 
 new_objects:
 
-	pc.flags = gfpflags;
+	trynode_flags = gfpflags;
 	/*
 	 * When a preferred node is indicated but no __GFP_THISNODE
 	 *
@@ -4479,17 +4476,16 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		     && try_thisnode)) {
 		if (unlikely(!allow_spin))
 			/* Do not upgrade gfp to NOWAIT from more restrictive mode */
-			pc.flags = gfpflags | __GFP_THISNODE;
+			trynode_flags = gfpflags | __GFP_THISNODE;
 		else
-			pc.flags = GFP_NOWAIT | __GFP_THISNODE;
+			trynode_flags = GFP_NOWAIT | __GFP_THISNODE;
 	}
 
-	pc.orig_size = ac->orig_size;
-	object = get_from_partial(s, node, &pc);
+	object = get_from_partial(s, node, trynode_flags, ac);
 	if (object)
 		goto success;
 
-	slab = new_slab(s, pc.flags, node);
+	slab = new_slab(s, trynode_flags, node);
 
 	if (unlikely(!slab)) {
 		if (node != NUMA_NO_NODE && !(gfpflags & __GFP_THISNODE)

-- 
2.54.0

[PATCH RFC 07/15] mm/slab: pass alloc_flags to new slab allocation

[Vlastimil Babka (SUSE)]

Add the alloc_flags parameter to allocate_slab() and new_slab()
so it can be used to determine if spinning is allowed, independently
from gfp flags.

refill_objects() passes SLAB_ALLOC_DEFAULT because it can only be
reached from contexts that allow spinning.

Also change how trynode_flags are constructed in ___slab_alloc() to
achieve the same "do not upgrade to GFP_NOWAIT" by using masking instead
of a branch. It will now also not upgrade in cases where gfp is weaker
than GFP_NOWAIT (i.e. lacks __GFP_KSWAPD_RECLAIM) but doesn't come from
kmalloc_nolock() - which is more correct anyway.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 0bde4f6d9126..20df6b131f63 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3378,9 +3378,10 @@ static __always_inline void unaccount_slab(struct slab *slab, int order,
 }
 
 /* Allocate and initialize a slab without building its freelist. */
-static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
+static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,
+				  unsigned int alloc_flags, int node)
 {
-	bool allow_spin = gfpflags_allow_spinning(flags);
+	bool allow_spin = alloc_flags_allow_spinning(alloc_flags);
 	struct slab *slab;
 	struct kmem_cache_order_objects oo = s->oo;
 	gfp_t alloc_gfp;
@@ -3438,15 +3439,17 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	return slab;
 }
 
-static struct slab *new_slab(struct kmem_cache *s, gfp_t flags, int node)
+static struct slab *new_slab(struct kmem_cache *s, gfp_t flags,
+			     unsigned int alloc_flags, int node)
 {
 	if (unlikely(flags & GFP_SLAB_BUG_MASK))
 		flags = kmalloc_fix_flags(flags);
 
 	WARN_ON_ONCE(s->ctor && (flags & __GFP_ZERO));
 
-	return allocate_slab(s,
-		flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
+	flags &= GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK;
+
+	return allocate_slab(s, flags, alloc_flags, node);
 }
 
 static void __free_slab(struct kmem_cache *s, struct slab *slab, bool allow_spin)
@@ -4467,25 +4470,22 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 	 * 1) try to get a partial slab from target node only by having
 	 *    __GFP_THISNODE in pc.flags for get_from_partial()
 	 * 2) if 1) failed, try to allocate a new slab from target node with
-	 *    GPF_NOWAIT | __GFP_THISNODE opportunistically
+	 *    (at most) GPF_NOWAIT | __GFP_THISNODE opportunistically
 	 * 3) if 2) failed, retry with original gfpflags which will allow
 	 *    get_from_partial() try partial lists of other nodes before
 	 *    potentially allocating new page from other nodes
 	 */
 	if (unlikely(node != NUMA_NO_NODE && !(gfpflags & __GFP_THISNODE)
 		     && try_thisnode)) {
-		if (unlikely(!allow_spin))
-			/* Do not upgrade gfp to NOWAIT from more restrictive mode */
-			trynode_flags = gfpflags | __GFP_THISNODE;
-		else
-			trynode_flags = GFP_NOWAIT | __GFP_THISNODE;
+		trynode_flags &= GFP_NOWAIT;
+		trynode_flags |= __GFP_NOWARN | __GFP_THISNODE;
 	}
 
 	object = get_from_partial(s, node, trynode_flags, ac);
 	if (object)
 		goto success;
 
-	slab = new_slab(s, trynode_flags, node);
+	slab = new_slab(s, trynode_flags, ac->alloc_flags, node);
 
 	if (unlikely(!slab)) {
 		if (node != NUMA_NO_NODE && !(gfpflags & __GFP_THISNODE)
@@ -7215,7 +7215,7 @@ refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min,
 
 new_slab:
 
-	slab = new_slab(s, gfp, local_node);
+	slab = new_slab(s, gfp, SLAB_ALLOC_DEFAULT, local_node);
 	if (!slab)
 		goto out;
 
@@ -7563,7 +7563,7 @@ static void early_kmem_cache_node_alloc(int node)
 
 	BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node));
 
-	slab = new_slab(kmem_cache_node, GFP_NOWAIT, node);
+	slab = new_slab(kmem_cache_node, GFP_NOWAIT, SLAB_ALLOC_DEFAULT, node);
 
 	BUG_ON(!slab);
 	if (slab_nid(slab) != node) {

-- 
2.54.0

[PATCH RFC 08/15] mm/slab: pass alloc_flags through slab_post_alloc_hook() chain

[Vlastimil Babka (SUSE)]

Convert the whole following call stack to pass either slab_alloc_context
(thus including alloc_flags) or just alloc_flags as necessary:

slab_post_alloc_hook()
  alloc_tagging_slab_alloc_hook()
    __alloc_tagging_slab_alloc_hook()
      prepare_slab_obj_exts_hook()
        alloc_slab_obj_exts()
  memcg_slab_post_alloc_hook()
    __memcg_slab_post_alloc_hook()
      alloc_slab_obj_exts()

Converting all these at once avoids unnecessary churn and is mostly
mechanical.

This ultimately allows to decide if spinning is allowed using
alloc_flags in alloc_slab_obj_exts(), as well as slab_post_alloc_hook().
Aside from alloc_from_pcs_bulk() (to be handled next) there is nothing
else in slab itself relying on gfpflags_allow_spinning() which can
be false even if not called from kmalloc_nolock().

A followup change will also use the alloc_flags availability in the call
stack above to remove the __GFP_NO_OBJ_EXT flag.

For alloc_slab_obj_exts(), also replace the suboptimal "bool new_slab"
parameter with a SLAB_ALLOC_NEW_SLAB flag with identical functionality.

To further reduce the number of parameters of slab_post_alloc_hook(),
also make 'struct list_lru *lru' (which is NULL for most callers) a new
field of slab_alloc_context.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/memcontrol.c |  5 +--
 mm/slab.h       |  6 ++--
 mm/slub.c       | 94 +++++++++++++++++++++++++++++++++------------------------
 3 files changed, 62 insertions(+), 43 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c03d4787d466..29390ba13baa 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3424,7 +3424,8 @@ static inline size_t obj_full_size(struct kmem_cache *s)
 }
 
 bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
-				  gfp_t flags, size_t size, void **p)
+				  gfp_t flags, unsigned int slab_alloc_flags,
+				  size_t size, void **p)
 {
 	size_t obj_size = obj_full_size(s);
 	struct obj_cgroup *objcg;
@@ -3472,7 +3473,7 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 		slab = virt_to_slab(p[i]);
 
 		if (!slab_obj_exts(slab) &&
-		    alloc_slab_obj_exts(slab, s, flags, false)) {
+		    alloc_slab_obj_exts(slab, s, flags, slab_alloc_flags)) {
 			continue;
 		}
 
diff --git a/mm/slab.h b/mm/slab.h
index 3e75182ee144..13517abcad21 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -19,6 +19,7 @@
 /* slab's alloc_flags definitions */
 #define SLAB_ALLOC_DEFAULT	0x00
 #define SLAB_ALLOC_TRYLOCK	0x01
+#define SLAB_ALLOC_NEW_SLAB	0x02 /* a flag for alloc_slab_obj_exts() */
 
 static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags)
 {
@@ -612,7 +613,7 @@ static inline struct slabobj_ext *slab_obj_ext(struct slab *slab,
 }
 
 int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
-                        gfp_t gfp, bool new_slab);
+                        gfp_t gfp, unsigned int alloc_flags);
 
 #else /* CONFIG_SLAB_OBJ_EXT */
 
@@ -642,7 +643,8 @@ static inline enum node_stat_item cache_vmstat_idx(struct kmem_cache *s)
 
 #ifdef CONFIG_MEMCG
 bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
-				  gfp_t flags, size_t size, void **p);
+				  gfp_t flags, unsigned int slab_alloc_flags,
+				  size_t size, void **p);
 void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
 			    void **p, int objects, unsigned long obj_exts);
 #endif
diff --git a/mm/slub.c b/mm/slub.c
index 20df6b131f63..034f2cd1c1fd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -218,6 +218,7 @@ struct slab_alloc_context {
 	unsigned long caller_addr;
 	unsigned long orig_size;
 	unsigned int alloc_flags;
+	struct list_lru *lru;
 };
 
 /* Structure holding parameters for get_partial_node_bulk() */
@@ -2155,9 +2156,9 @@ static inline size_t obj_exts_alloc_size(struct kmem_cache *s,
 }
 
 int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
-		        gfp_t gfp, bool new_slab)
+		        gfp_t gfp, unsigned int alloc_flags)
 {
-	bool allow_spin = gfpflags_allow_spinning(gfp);
+	const bool allow_spin = alloc_flags_allow_spinning(alloc_flags);
 	unsigned int objects = objs_per_slab(s, slab);
 	unsigned long new_exts;
 	unsigned long old_exts;
@@ -2206,7 +2207,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 	old_exts = READ_ONCE(slab->obj_exts);
 	handle_failed_objexts_alloc(old_exts, vec, objects);
 
-	if (new_slab) {
+	if (alloc_flags & SLAB_ALLOC_NEW_SLAB) {
 		/*
 		 * If the slab is brand new and nobody can yet access its
 		 * obj_exts, no synchronization is required and obj_exts can
@@ -2331,7 +2332,7 @@ static inline void init_slab_obj_exts(struct slab *slab)
 }
 
 static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
-			       gfp_t gfp, bool new_slab)
+			       gfp_t gfp, unsigned int alloc_flags)
 {
 	return 0;
 }
@@ -2351,10 +2352,10 @@ static inline void alloc_slab_obj_exts_early(struct kmem_cache *s,
 
 static inline unsigned long
 prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,
-			   gfp_t flags, void *p)
+			   gfp_t flags, unsigned int alloc_flags, void *p)
 {
 	if (!slab_obj_exts(slab) &&
-	    alloc_slab_obj_exts(slab, s, flags, false)) {
+	    alloc_slab_obj_exts(slab, s, flags, alloc_flags)) {
 		pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
 			     __func__, s->name);
 		return 0;
@@ -2366,7 +2367,8 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, struct slab *slab,
 
 /* Should be called only if mem_alloc_profiling_enabled() */
 static noinline void
-__alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
+__alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
+				unsigned int alloc_flags)
 {
 	unsigned long obj_exts;
 	struct slabobj_ext *obj_ext;
@@ -2382,7 +2384,7 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
 		return;
 
 	slab = virt_to_slab(object);
-	obj_exts = prepare_slab_obj_exts_hook(s, slab, flags, object);
+	obj_exts = prepare_slab_obj_exts_hook(s, slab, flags, alloc_flags, object);
 	/*
 	 * Currently obj_exts is used only for allocation profiling.
 	 * If other users appear then mem_alloc_profiling_enabled()
@@ -2401,10 +2403,11 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
 }
 
 static inline void
-alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
+alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
+			      unsigned int alloc_flags)
 {
 	if (mem_alloc_profiling_enabled())
-		__alloc_tagging_slab_alloc_hook(s, object, flags);
+		__alloc_tagging_slab_alloc_hook(s, object, flags, alloc_flags);
 }
 
 /* Should be called only if mem_alloc_profiling_enabled() */
@@ -2443,7 +2446,8 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 #else /* CONFIG_MEM_ALLOC_PROFILING */
 
 static inline void
-alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
+alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
+			      unsigned int alloc_flags)
 {
 }
 
@@ -2461,8 +2465,9 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p,
 static void memcg_alloc_abort_single(struct kmem_cache *s, void *object);
 
 static __fastpath_inline
-bool memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
-				gfp_t flags, size_t size, void **p)
+bool memcg_slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
+				size_t size, void **p,
+				struct slab_alloc_context *ac)
 {
 	if (likely(!memcg_kmem_online()))
 		return true;
@@ -2470,7 +2475,8 @@ bool memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 	if (likely(!(flags & __GFP_ACCOUNT) && !(s->flags & SLAB_ACCOUNT)))
 		return true;
 
-	if (likely(__memcg_slab_post_alloc_hook(s, lru, flags, size, p)))
+	if (likely(__memcg_slab_post_alloc_hook(s, ac->lru, flags,
+						ac->alloc_flags, size, p)))
 		return true;
 
 	if (likely(size == 1)) {
@@ -2558,14 +2564,15 @@ bool memcg_slab_post_charge(void *p, gfp_t flags)
 		put_slab_obj_exts(obj_exts);
 	}
 
-	return __memcg_slab_post_alloc_hook(s, NULL, flags, 1, &p);
+	return __memcg_slab_post_alloc_hook(s, NULL, flags, SLAB_ALLOC_DEFAULT,
+					    1, &p);
 }
 
 #else /* CONFIG_MEMCG */
 static inline bool memcg_slab_post_alloc_hook(struct kmem_cache *s,
-					      struct list_lru *lru,
-					      gfp_t flags, size_t size,
-					      void **p)
+					      gfp_t flags,
+					      size_t size, void **p,
+					      struct slab_alloc_context *ac)
 {
 	return true;
 }
@@ -3352,12 +3359,14 @@ static inline void init_freelist_randomization(void) { }
 #endif /* CONFIG_SLAB_FREELIST_RANDOM */
 
 static __always_inline void account_slab(struct slab *slab, int order,
-					 struct kmem_cache *s, gfp_t gfp)
+					 struct kmem_cache *s, gfp_t gfp,
+					 unsigned int alloc_flags)
 {
 	if (memcg_kmem_online() &&
 			(s->flags & SLAB_ACCOUNT) &&
 			!slab_obj_exts(slab))
-		alloc_slab_obj_exts(slab, s, gfp, true);
+		alloc_slab_obj_exts(slab, s, gfp,
+				    alloc_flags | SLAB_ALLOC_NEW_SLAB);
 
 	mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),
 			    PAGE_SIZE << order);
@@ -3434,7 +3443,7 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags,
 	 * to prevent the array from being overwritten.
 	 */
 	alloc_slab_obj_exts_early(s, slab);
-	account_slab(slab, oo_order(oo), s, flags);
+	account_slab(slab, oo_order(oo), s, flags, alloc_flags);
 
 	return slab;
 }
@@ -4568,9 +4577,8 @@ struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
 }
 
 static __fastpath_inline
-bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
-			  gfp_t flags, size_t size, void **p,
-			  unsigned int orig_size)
+bool slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, size_t size,
+			  void **p, struct slab_alloc_context *ac)
 {
 	bool init = slab_want_init_on_alloc(flags, s);
 	bool kasan_init = init;
@@ -4599,15 +4607,15 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
 		p[i] = kasan_slab_alloc(s, p[i], init_flags, kasan_init);
 		if (p[i] && init && (!kasan_init ||
 				     !kasan_has_integrated_init()))
-			memset(p[i], 0, orig_size);
-		if (gfpflags_allow_spinning(flags))
+			memset(p[i], 0, ac->orig_size);
+		if (alloc_flags_allow_spinning(ac->alloc_flags))
 			kmemleak_alloc_recursive(p[i], s->object_size, 1,
 						 s->flags, init_flags);
 		kmsan_slab_alloc(s, p[i], init_flags);
-		alloc_tagging_slab_alloc_hook(s, p[i], flags);
+		alloc_tagging_slab_alloc_hook(s, p[i], flags, ac->alloc_flags);
 	}
 
-	return memcg_slab_post_alloc_hook(s, lru, flags, size, p);
+	return memcg_slab_post_alloc_hook(s, flags, size, p, ac);
 }
 
 /*
@@ -4902,6 +4910,12 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 {
 	const unsigned int alloc_flags = SLAB_ALLOC_DEFAULT;
 	void *object;
+	struct slab_alloc_context ac = {
+		.caller_addr = addr,
+		.orig_size = orig_size,
+		.alloc_flags = alloc_flags,
+		.lru = lru,
+	};
 
 	s = slab_pre_alloc_hook(s, gfpflags);
 	if (unlikely(!s))
@@ -4913,14 +4927,8 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 
 	object = alloc_from_pcs(s, gfpflags, alloc_flags, node);
 
-	if (unlikely(!object)) {
-		struct slab_alloc_context ac = {
-			.caller_addr = addr,
-			.orig_size = orig_size,
-			.alloc_flags = alloc_flags,
-		};
+	if (!object)
 		object = __slab_alloc_node(s, gfpflags, node, &ac);
-	}
 
 	maybe_wipe_obj_freeptr(s, object);
 
@@ -4929,7 +4937,7 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 	 * In case this fails due to memcg_slab_post_alloc_hook(),
 	 * object is set to NULL
 	 */
-	slab_post_alloc_hook(s, lru, gfpflags, 1, &object, orig_size);
+	slab_post_alloc_hook(s, gfpflags, 1, &object, &ac);
 
 	return object;
 }
@@ -5224,6 +5232,10 @@ kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp,
 				   struct slab_sheaf *sheaf)
 {
 	void *ret = NULL;
+	struct slab_alloc_context ac = {
+		.orig_size = s->object_size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
 
 	if (sheaf->size == 0)
 		goto out;
@@ -5234,7 +5246,7 @@ kmem_cache_alloc_from_sheaf_noprof(struct kmem_cache *s, gfp_t gfp,
 		ret = sheaf->objects[--sheaf->size];
 
 	/* add __GFP_NOFAIL to force successful memcg charging */
-	slab_post_alloc_hook(s, NULL, gfp | __GFP_NOFAIL, 1, &ret, s->object_size);
+	slab_post_alloc_hook(s, gfp | __GFP_NOFAIL, 1, &ret, &ac);
 out:
 	trace_kmem_cache_alloc(_RET_IP_, ret, s, gfp, NUMA_NO_NODE);
 
@@ -5421,7 +5433,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 
 success:
 	maybe_wipe_obj_freeptr(s, ret);
-	slab_post_alloc_hook(s, NULL, alloc_gfp, 1, &ret, orig_size);
+	slab_post_alloc_hook(s, alloc_gfp, 1, &ret, &ac);
 
 	ret = kasan_kmalloc(s, ret, orig_size, alloc_gfp);
 	return ret;
@@ -7287,6 +7299,10 @@ bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,
 {
 	unsigned int i = 0;
 	void *kfence_obj;
+	struct slab_alloc_context ac = {
+		.orig_size = s->object_size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
 
 	if (!size)
 		return false;
@@ -7337,7 +7353,7 @@ bool kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags,
 
 out:
 	/* memcg and kmem_cache debug support and memory initialization */
-	return likely(slab_post_alloc_hook(s, NULL, flags, size, p, s->object_size));
+	return likely(slab_post_alloc_hook(s, flags, size, p, &ac));
 }
 EXPORT_SYMBOL(kmem_cache_alloc_bulk_noprof);
 

-- 
2.54.0

[PATCH RFC 09/15] mm/slab: replace slab_alloc_node() parameters with slab_alloc_context

[Vlastimil Babka (SUSE)]

The function takes all the parameters that exist as fields in
slab_alloc_context, except alloc_flags. Replace them with a single
pointer.

This moves slab_alloc_context initialization to a number of callers,
which is more verbose, but arguably also more clear than a long list of
parameters, and most do not use the 'lru' field.

This will also allow kmalloc_nolock() to call slab_alloc_node() and
reduce the special open-coding it currently has.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 75 ++++++++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 53 insertions(+), 22 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 034f2cd1c1fd..b511d768e9b6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4905,30 +4905,23 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
  *
  * Otherwise we can simply pick the next object from the lockless free list.
  */
-static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list_lru *lru,
-		gfp_t gfpflags, int node, unsigned long addr, size_t orig_size)
+static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s,
+		gfp_t gfpflags, int node, struct slab_alloc_context *ac)
 {
-	const unsigned int alloc_flags = SLAB_ALLOC_DEFAULT;
 	void *object;
-	struct slab_alloc_context ac = {
-		.caller_addr = addr,
-		.orig_size = orig_size,
-		.alloc_flags = alloc_flags,
-		.lru = lru,
-	};
 
 	s = slab_pre_alloc_hook(s, gfpflags);
 	if (unlikely(!s))
 		return NULL;
 
-	object = kfence_alloc(s, orig_size, gfpflags);
+	object = kfence_alloc(s, ac->orig_size, gfpflags);
 	if (unlikely(object))
 		goto out;
 
-	object = alloc_from_pcs(s, gfpflags, alloc_flags, node);
+	object = alloc_from_pcs(s, gfpflags, ac->alloc_flags, node);
 
 	if (!object)
-		object = __slab_alloc_node(s, gfpflags, node, &ac);
+		object = __slab_alloc_node(s, gfpflags, node, ac);
 
 	maybe_wipe_obj_freeptr(s, object);
 
@@ -4937,15 +4930,21 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
 	 * In case this fails due to memcg_slab_post_alloc_hook(),
 	 * object is set to NULL
 	 */
-	slab_post_alloc_hook(s, gfpflags, 1, &object, &ac);
+	slab_post_alloc_hook(s, gfpflags, 1, &object, ac);
 
 	return object;
 }
 
 void *kmem_cache_alloc_noprof(struct kmem_cache *s, gfp_t gfpflags)
 {
-	void *ret = slab_alloc_node(s, NULL, gfpflags, NUMA_NO_NODE, _RET_IP_,
-				    s->object_size);
+	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = s->object_size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
+	ret = slab_alloc_node(s, gfpflags, NUMA_NO_NODE, &ac);
 
 	trace_kmem_cache_alloc(_RET_IP_, ret, s, gfpflags, NUMA_NO_NODE);
 
@@ -4956,8 +4955,15 @@ EXPORT_SYMBOL(kmem_cache_alloc_noprof);
 void *kmem_cache_alloc_lru_noprof(struct kmem_cache *s, struct list_lru *lru,
 			   gfp_t gfpflags)
 {
-	void *ret = slab_alloc_node(s, lru, gfpflags, NUMA_NO_NODE, _RET_IP_,
-				    s->object_size);
+	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = s->object_size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+		.lru = lru,
+	};
+
+	ret = slab_alloc_node(s, gfpflags, NUMA_NO_NODE, &ac);
 
 	trace_kmem_cache_alloc(_RET_IP_, ret, s, gfpflags, NUMA_NO_NODE);
 
@@ -4989,7 +4995,14 @@ EXPORT_SYMBOL(kmem_cache_charge);
  */
 void *kmem_cache_alloc_node_noprof(struct kmem_cache *s, gfp_t gfpflags, int node)
 {
-	void *ret = slab_alloc_node(s, NULL, gfpflags, node, _RET_IP_, s->object_size);
+	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = s->object_size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
+	ret = slab_alloc_node(s, gfpflags, node, &ac);
 
 	trace_kmem_cache_alloc(_RET_IP_, ret, s, gfpflags, node);
 
@@ -5319,6 +5332,11 @@ void *__do_kmalloc_node(size_t size, kmem_buckets *b, gfp_t flags, int node,
 {
 	struct kmem_cache *s;
 	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = caller,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
 
 	if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) {
 		ret = __kmalloc_large_node_noprof(size, flags, node);
@@ -5332,7 +5350,7 @@ void *__do_kmalloc_node(size_t size, kmem_buckets *b, gfp_t flags, int node,
 
 	s = kmalloc_slab(size, b, flags, token);
 
-	ret = slab_alloc_node(s, NULL, flags, node, caller, size);
+	ret = slab_alloc_node(s, flags, node, &ac);
 	ret = kasan_kmalloc(s, ret, size, flags);
 	trace_kmalloc(caller, ret, size, s->size, flags, node);
 	return ret;
@@ -5451,8 +5469,14 @@ EXPORT_SYMBOL(__kmalloc_node_track_caller_noprof);
 
 void *__kmalloc_cache_noprof(struct kmem_cache *s, gfp_t gfpflags, size_t size)
 {
-	void *ret = slab_alloc_node(s, NULL, gfpflags, NUMA_NO_NODE,
-					    _RET_IP_, size);
+	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
+	ret = slab_alloc_node(s, gfpflags, NUMA_NO_NODE, &ac);
 
 	trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags, NUMA_NO_NODE);
 
@@ -5464,7 +5488,14 @@ EXPORT_SYMBOL(__kmalloc_cache_noprof);
 void *__kmalloc_cache_node_noprof(struct kmem_cache *s, gfp_t gfpflags,
 				  int node, size_t size)
 {
-	void *ret = slab_alloc_node(s, NULL, gfpflags, node, _RET_IP_, size);
+	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
+	ret = slab_alloc_node(s, gfpflags, node, &ac);
 
 	trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags, node);
 

-- 
2.54.0

[PATCH RFC 10/15] mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags

[Vlastimil Babka (SUSE)]

The last user of gfpflags_allow_spinning() in slab is
alloc_from_pcs_bulk(), which is only called from
kmem_cache_alloc_bulk().

It turns out that gfpflags_allow_spinning() is not necessary, because
kmem_cache_alloc_bulk() is only expected to be called from context that
does allow spinning, so simply replace it with 'true'.

With that, we can remove the "@flags must allow spinning" part of the
kernel doc, as there is no more connection to the gfp flags in the slab
implementation.

Also remove a comment in alloc_slab_obj_exts() because there should be
no more false positives possible due to gfp_allowed_mask during early
boot.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index b511d768e9b6..dee69e0b7780 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2171,12 +2171,6 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 
 	sz = obj_exts_alloc_size(s, slab, gfp);
 
-	/*
-	 * Note that allow_spin may be false during early boot and its
-	 * restricted GFP_BOOT_MASK. Due to kmalloc_nolock() only supporting
-	 * architectures with cmpxchg16b, early obj_exts will be missing for
-	 * very early allocations on those.
-	 */
 	if (unlikely(!allow_spin))
 		vec = kmalloc_nolock(sz, __GFP_ZERO | __GFP_NO_OBJ_EXT,
 				     slab_nid(slab));
@@ -4851,7 +4845,7 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
 		}
 
 		full = barn_replace_empty_sheaf(barn, pcs->main,
-						gfpflags_allow_spinning(gfp));
+						/* allow_spin = */ true);
 
 		if (full) {
 			stat(s, BARN_GET);
@@ -7317,8 +7311,7 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
  * Allocate @size objects from @s and places them into @p.  @size must be larger
  * than 0.
  *
- * Interrupts must be enabled when calling this function and @flags must allow
- * spinning.
+ * Interrupts must be enabled when calling this function.
  *
  * Unlike alloc_pages_bulk(), this function does not check for already allocated
  * objects in @p, and thus the caller does not need to zero it.

-- 
2.54.0

[PATCH RFC 11/15] mm/slab: pass slab_alloc_context to __do_kmalloc_node()

[Vlastimil Babka (SUSE)]

With alloc_flags usage in slab, we can replace __GFP_NO_OBJ_EXT with an
alloc flag that prevents kmalloc recursion. For that we need a version
of kmalloc() that takes alloc_flags and use it in places that perform
these potentially recursive kmalloc allocations (of sheaves or obj_ext
arrays).

As a preparatory step, make __do_kmalloc_node() take a pointer to
slab_alloc_context. This replaces the 'caller' parameter and includes
alloc_flags which we'll make use of.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 47 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index dee69e0b7780..c11edd58b52d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5322,19 +5322,14 @@ EXPORT_SYMBOL(__kmalloc_large_node_noprof);
 
 static __always_inline
 void *__do_kmalloc_node(size_t size, kmem_buckets *b, gfp_t flags, int node,
-			unsigned long caller, kmalloc_token_t token)
+			kmalloc_token_t token, struct slab_alloc_context *ac)
 {
 	struct kmem_cache *s;
 	void *ret;
-	struct slab_alloc_context ac = {
-		.caller_addr = caller,
-		.orig_size = size,
-		.alloc_flags = SLAB_ALLOC_DEFAULT,
-	};
 
 	if (unlikely(size > KMALLOC_MAX_CACHE_SIZE)) {
 		ret = __kmalloc_large_node_noprof(size, flags, node);
-		trace_kmalloc(caller, ret, size,
+		trace_kmalloc(ac->caller_addr, ret, size,
 			      PAGE_SIZE << get_order(size), flags, node);
 		return ret;
 	}
@@ -5344,22 +5339,34 @@ void *__do_kmalloc_node(size_t size, kmem_buckets *b, gfp_t flags, int node,
 
 	s = kmalloc_slab(size, b, flags, token);
 
-	ret = slab_alloc_node(s, flags, node, &ac);
+	ret = slab_alloc_node(s, flags, node, ac);
 	ret = kasan_kmalloc(s, ret, size, flags);
-	trace_kmalloc(caller, ret, size, s->size, flags, node);
+	trace_kmalloc(ac->caller_addr, ret, size, s->size, flags, node);
 	return ret;
 }
 void *__kmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags, int node)
 {
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
 	return __do_kmalloc_node(size, PASS_BUCKET_PARAM(b), flags, node,
-				 _RET_IP_, PASS_TOKEN_PARAM(token));
+				 PASS_TOKEN_PARAM(token), &ac);
 }
 EXPORT_SYMBOL(__kmalloc_node_noprof);
 
 void *__kmalloc_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags)
 {
-	return __do_kmalloc_node(size, NULL, flags,  NUMA_NO_NODE, _RET_IP_,
-				 PASS_TOKEN_PARAM(token));
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
+
+	return __do_kmalloc_node(size, NULL, flags,  NUMA_NO_NODE,
+				 PASS_TOKEN_PARAM(token), &ac);
 }
 EXPORT_SYMBOL(__kmalloc_noprof);
 
@@ -5455,9 +5462,14 @@ EXPORT_SYMBOL_GPL(_kmalloc_nolock_noprof);
 void *__kmalloc_node_track_caller_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags,
 					 int node, unsigned long caller)
 {
-	return __do_kmalloc_node(size, PASS_BUCKET_PARAM(b), flags, node,
-				 caller, PASS_TOKEN_PARAM(token));
+	struct slab_alloc_context ac = {
+		.caller_addr = caller,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
 
+	return __do_kmalloc_node(size, PASS_BUCKET_PARAM(b), flags, node,
+				 PASS_TOKEN_PARAM(token), &ac);
 }
 EXPORT_SYMBOL(__kmalloc_node_track_caller_noprof);
 
@@ -6858,6 +6870,11 @@ void *__kvmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), unsigned long
 {
 	bool allow_block;
 	void *ret;
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_DEFAULT,
+	};
 
 	/*
 	 * It doesn't really make sense to fallback to vmalloc for sub page
@@ -6865,7 +6882,7 @@ void *__kvmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), unsigned long
 	 */
 	ret = __do_kmalloc_node(size, PASS_BUCKET_PARAM(b),
 				kmalloc_gfp_adjust(flags, size),
-				node, _RET_IP_, PASS_TOKEN_PARAM(token));
+				node, PASS_TOKEN_PARAM(token), &ac);
 	if (ret || size <= PAGE_SIZE)
 		return ret;
 

-- 
2.54.0

[PATCH RFC 12/15] mm/slab: introduce kmalloc_flags()

[Vlastimil Babka (SUSE)]

With alloc_flags usage in slab, we can replace __GFP_NO_OBJ_EXT with an
alloc flag that prevents kmalloc recursion. For that we need a version
of kmalloc() that takes alloc_flags and use it in places that perform
these potentially recursive kmalloc allocations (of sheaves or obj_ext
arrays).

Add this function, named kmalloc_flags(). Right now it's only useful for
these nested allocations, so it doesn't need to optimize build-time
constant sizes like kmalloc() or kmalloc_buckets.

Since we need it to support both normal and non-spinning
kmalloc_nolock() context through the SLAB_ALLOC_TRYLOCK flag, split out
most of the special _kmalloc_nolock_noprof() implementation to
__kmalloc_nolock_noprof() that takes a slab_alloc_context, and make
_kmalloc_nolock_noprof() a simple tail calling wrapper with the proper
context.

kmalloc_flags() can thus determine whether to call
__kmalloc_nolock_noprof() or __do_kmalloc_node(), based on the
given alloc_flags.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 include/linux/slab.h | 12 +++++++++++
 mm/slub.c            | 56 ++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index ce1c867dc0ba..11e82fdbe8d3 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -944,6 +944,10 @@ void *__kmalloc_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags)
 void *__kmalloc_node_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags, int node)
 				__assume_kmalloc_alignment __alloc_size(1);
 
+void *__kmalloc_flags_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags,
+				  unsigned int alloc_flags, int node)
+				  __assume_kmalloc_alignment __alloc_size(1);
+
 void *__kmalloc_cache_noprof(struct kmem_cache *s, gfp_t flags, size_t size)
 				__assume_kmalloc_alignment __alloc_size(3);
 
@@ -1176,6 +1180,14 @@ static __always_inline __alloc_size(1) void *_kmalloc_node_noprof(size_t size, g
 #define kmalloc_node_noprof(...)		_kmalloc_node_noprof(__VA_ARGS__, __kmalloc_token(__VA_ARGS__))
 #define kmalloc_node(...)			alloc_hooks(kmalloc_node_noprof(__VA_ARGS__))
 
+static __always_inline __alloc_size(1) void *_kmalloc_flags_noprof(size_t size,
+		gfp_t flags, unsigned int alloc_flags, int node, kmalloc_token_t token)
+{
+	return __kmalloc_flags_noprof(PASS_TOKEN_PARAMS(size, token), flags, alloc_flags, node);
+}
+#define kmalloc_flags_noprof(...)		_kmalloc_flags_noprof(__VA_ARGS__, __kmalloc_token(__VA_ARGS__))
+#define kmalloc_flags(...)			alloc_hooks(kmalloc_flags_noprof(__VA_ARGS__))
+
 static inline __alloc_size(1, 2) void *_kmalloc_array_noprof(size_t n, size_t size, gfp_t flags, kmalloc_token_t token)
 {
 	size_t bytes;
diff --git a/mm/slub.c b/mm/slub.c
index c11edd58b52d..86691eb14002 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5370,15 +5370,15 @@ void *__kmalloc_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags)
 }
 EXPORT_SYMBOL(__kmalloc_noprof);
 
-void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, int node)
+static void *__kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags,
+				     int node, struct slab_alloc_context *ac)
 {
 	gfp_t alloc_gfp = __GFP_NOWARN | __GFP_NOMEMALLOC | gfp_flags;
-	size_t orig_size = size;
-	unsigned int alloc_flags = SLAB_ALLOC_TRYLOCK;
 	struct kmem_cache *s;
 	bool can_retry = true;
 	void *ret;
 
+	VM_WARN_ON_ONCE(alloc_flags_allow_spinning(ac->alloc_flags));
 	VM_WARN_ON_ONCE(gfp_flags & ~(__GFP_ACCOUNT | __GFP_ZERO |
 				      __GFP_NO_OBJ_EXT));
 
@@ -5413,23 +5413,17 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 		 */
 		return NULL;
 
-	ret = alloc_from_pcs(s, alloc_gfp, alloc_flags, node);
+	ret = alloc_from_pcs(s, alloc_gfp, ac->alloc_flags, node);
 	if (ret)
 		goto success;
 
-	struct slab_alloc_context ac = {
-		.caller_addr = _RET_IP_,
-		.orig_size = orig_size,
-		.alloc_flags = alloc_flags,
-	};
-
 	/*
 	 * Do not call slab_alloc_node(), since trylock mode isn't
 	 * compatible with slab_pre_alloc_hook/should_failslab and
 	 * kfence_alloc. Hence call __slab_alloc_node() (at most twice)
 	 * and slab_post_alloc_hook() directly.
 	 */
-	ret = __slab_alloc_node(s, alloc_gfp, node, &ac);
+	ret = __slab_alloc_node(s, alloc_gfp, node, ac);
 
 	/*
 	 * It's possible we failed due to trylock as we preempted someone with
@@ -5452,11 +5446,23 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 
 success:
 	maybe_wipe_obj_freeptr(s, ret);
-	slab_post_alloc_hook(s, alloc_gfp, 1, &ret, &ac);
+	slab_post_alloc_hook(s, alloc_gfp, 1, &ret, ac);
 
-	ret = kasan_kmalloc(s, ret, orig_size, alloc_gfp);
+	ret = kasan_kmalloc(s, ret, ac->orig_size, alloc_gfp);
 	return ret;
 }
+
+void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, int node)
+{
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = SLAB_ALLOC_TRYLOCK,
+	};
+
+	return __kmalloc_nolock_noprof(PASS_TOKEN_PARAMS(size, token),
+				       gfp_flags, node, &ac);
+}
 EXPORT_SYMBOL_GPL(_kmalloc_nolock_noprof);
 
 void *__kmalloc_node_track_caller_noprof(DECL_KMALLOC_PARAMS(size, b, token), gfp_t flags,
@@ -5510,6 +5516,30 @@ void *__kmalloc_cache_node_noprof(struct kmem_cache *s, gfp_t gfpflags,
 }
 EXPORT_SYMBOL(__kmalloc_cache_node_noprof);
 
+/*
+ * The only version of kmalloc_node() that takes alloc_flags and thus can
+ * determine on its own whether to handle the allocation via kmalloc_nolock() or
+ * normally
+ */
+void *__kmalloc_flags_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t flags,
+			     unsigned int alloc_flags, int node)
+{
+	struct slab_alloc_context ac = {
+		.caller_addr = _RET_IP_,
+		.orig_size = size,
+		.alloc_flags = alloc_flags,
+	};
+
+	if (alloc_flags_allow_spinning(alloc_flags)) {
+		return __do_kmalloc_node(size, NULL, flags, node,
+				PASS_TOKEN_PARAM(token), &ac);
+	} else {
+		return __kmalloc_nolock_noprof(PASS_TOKEN_PARAMS(size, token),
+					       flags, node, &ac);
+	}
+}
+
+
 static noinline void free_to_partial_list(
 	struct kmem_cache *s, struct slab *slab,
 	void *head, void *tail, int bulk_cnt,

-- 
2.54.0

[PATCH RFC 13/15] mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts()

[Vlastimil Babka (SUSE)]

__GFP_NO_OBJ_EXT has limited scope within the slab allocator itself and
gfp flags are a scarce resource, unlike slab's alloc_flags.

Introduce SLAB_ALLOC_NO_RECURSE alloc flag that has the same intent as
__GFP_NO_OBJ_EXT but a more generic name, meaning that a kmalloc()
family function should not recurse into another kmalloc*() for the
purposes of allocating auxiliary structures (obj_ext arrays or sheaves).

First, replace the __GFP_NO_OBJ_EXT for allocating obj_ext arrays in
alloc_slab_obj_exts(). Make use of the newly added kmalloc_flags()
function, where we can pass alloc_flags with SLAB_ALLOC_NO_RECURSE
added. This will also pass through SLAB_ALLOC_TRYLOCK so we don't need
to special case kmalloc_nolock() anymore.

Note that until now the kmalloc_nolock() ignored the incoming gfp flags
and hardcoded __GFP_ZERO | __GFP_NO_OBJ_EXT. But it's correct to pass on
the incoming gfp flags (only augmented with __GFP_ZERO), because if
alloc_flags contain SLAB_ALLOC_TRYLOCK, the incoming gfp flags have to
be also compatible with it.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slab.h |  1 +
 mm/slub.c | 13 +++++--------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 13517abcad21..e5bd800d831e 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -20,6 +20,7 @@
 #define SLAB_ALLOC_DEFAULT	0x00
 #define SLAB_ALLOC_TRYLOCK	0x01
 #define SLAB_ALLOC_NEW_SLAB	0x02 /* a flag for alloc_slab_obj_exts() */
+#define SLAB_ALLOC_NO_RECURSE	0x04 /* prevent kmalloc() recursion */
 
 static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags)
 {
diff --git a/mm/slub.c b/mm/slub.c
index 86691eb14002..8a655636dee6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2167,15 +2167,12 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 
 	gfp &= ~OBJCGS_CLEAR_MASK;
 	/* Prevent recursive extension vector allocation */
-	gfp |= __GFP_NO_OBJ_EXT;
+	alloc_flags |= SLAB_ALLOC_NO_RECURSE;
 
 	sz = obj_exts_alloc_size(s, slab, gfp);
 
-	if (unlikely(!allow_spin))
-		vec = kmalloc_nolock(sz, __GFP_ZERO | __GFP_NO_OBJ_EXT,
-				     slab_nid(slab));
-	else
-		vec = kmalloc_node(sz, gfp | __GFP_ZERO, slab_nid(slab));
+	/* This will use kmalloc_nolock() if alloc_flags say so */
+	vec = kmalloc_flags(sz, gfp | __GFP_ZERO, alloc_flags, slab_nid(slab));
 
 	if (!vec) {
 		/*
@@ -2251,7 +2248,7 @@ static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)
 	}
 
 	/*
-	 * obj_exts was created with __GFP_NO_OBJ_EXT flag, therefore its
+	 * obj_exts was created with SLAB_ALLOC_NO_RECURSE flag, therefore its
 	 * corresponding extension will be NULL. alloc_tag_sub() will throw a
 	 * warning if slab has extensions but the extension of an object is
 	 * NULL, therefore replace NULL with CODETAG_EMPTY to indicate that
@@ -2374,7 +2371,7 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags,
 	if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE))
 		return;
 
-	if (flags & __GFP_NO_OBJ_EXT)
+	if (alloc_flags & SLAB_ALLOC_NO_RECURSE)
 		return;
 
 	slab = virt_to_slab(object);

-- 
2.54.0

[PATCH RFC 14/15] mm/slab: replace __GFP_NO_OBJ_EXT with SLAB_ALLOC_NO_RECURSE for sheaves

[Vlastimil Babka (SUSE)]

Finish the switch away from __GFP_NO_OBJ_EXT by replacing it with
SLAB_ALLOC_NO_RECURSE when allocating empty sheaves. Pass alloc_flags to
[__]alloc_empty_sheaf(). Callers that can't be part of a recursive
kmalloc() chain simply pass SLAB_ALLOC_DEFAULT. Use kmalloc_flags()
instead of kzalloc() for allocating the sheaf.

This leaves __GFP_NO_OBJ_EXT with no users, to be removed next.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 mm/slub.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8a655636dee6..26ec015efdba 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2756,7 +2756,7 @@ static inline void *setup_object(struct kmem_cache *s, void *object)
 }
 
 static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
-					      unsigned int capacity)
+				unsigned int alloc_flags, unsigned int capacity)
 {
 	struct slab_sheaf *sheaf;
 	size_t sheaf_size;
@@ -2767,10 +2767,10 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
 	 * bucket)
 	 */
 	if (s->flags & SLAB_KMALLOC)
-		gfp |= __GFP_NO_OBJ_EXT;
+		alloc_flags |= SLAB_ALLOC_NO_RECURSE;
 
 	sheaf_size = struct_size(sheaf, objects, capacity);
-	sheaf = kzalloc(sheaf_size, gfp);
+	sheaf = kmalloc_flags(sheaf_size, gfp | __GFP_ZERO, alloc_flags, NUMA_NO_NODE);
 
 	if (unlikely(!sheaf))
 		return NULL;
@@ -2783,20 +2783,20 @@ static struct slab_sheaf *__alloc_empty_sheaf(struct kmem_cache *s, gfp_t gfp,
 }
 
 static inline struct slab_sheaf *alloc_empty_sheaf(struct kmem_cache *s,
-						   gfp_t gfp)
+				gfp_t gfp, unsigned int alloc_flags)
 {
-	if (gfp & __GFP_NO_OBJ_EXT)
+	if (alloc_flags & SLAB_ALLOC_NO_RECURSE)
 		return NULL;
 
 	gfp &= ~OBJCGS_CLEAR_MASK;
 
-	return __alloc_empty_sheaf(s, gfp, s->sheaf_capacity);
+	return __alloc_empty_sheaf(s, gfp, alloc_flags, s->sheaf_capacity);
 }
 
 static void free_empty_sheaf(struct kmem_cache *s, struct slab_sheaf *sheaf)
 {
 	/*
-	 * If the sheaf was created with __GFP_NO_OBJ_EXT flag then its
+	 * If the sheaf was created with SLAB_ALLOC_NO_RECURSE flag then its
 	 * corresponding extension is NULL and alloc_tag_sub() will throw a
 	 * warning, therefore replace NULL with CODETAG_EMPTY to indicate
 	 * that the extension for this sheaf is expected to be NULL.
@@ -4673,7 +4673,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,
 		return NULL;
 
 	if (!empty) {
-		empty = alloc_empty_sheaf(s, gfp);
+		empty = alloc_empty_sheaf(s, gfp, alloc_flags);
 		if (!empty)
 			return NULL;
 	}
@@ -5047,7 +5047,7 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
 
 	if (unlikely(size > s->sheaf_capacity)) {
 
-		sheaf = __alloc_empty_sheaf(s, gfp, size);
+		sheaf = __alloc_empty_sheaf(s, gfp, SLAB_ALLOC_DEFAULT, size);
 		if (!sheaf)
 			return NULL;
 
@@ -5092,7 +5092,7 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size)
 
 
 	if (!sheaf)
-		sheaf = alloc_empty_sheaf(s, gfp);
+		sheaf = alloc_empty_sheaf(s, gfp, SLAB_ALLOC_DEFAULT);
 
 	if (sheaf) {
 		sheaf->capacity = s->sheaf_capacity;
@@ -5376,8 +5376,7 @@ static void *__kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_f
 	void *ret;
 
 	VM_WARN_ON_ONCE(alloc_flags_allow_spinning(ac->alloc_flags));
-	VM_WARN_ON_ONCE(gfp_flags & ~(__GFP_ACCOUNT | __GFP_ZERO |
-				      __GFP_NO_OBJ_EXT));
+	VM_WARN_ON_ONCE(gfp_flags & ~(__GFP_ACCOUNT | __GFP_ZERO));
 
 	if (unlikely(!size))
 		return ZERO_SIZE_PTR;
@@ -5890,7 +5889,7 @@ __pcs_replace_full_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs,
 	if (!allow_spin)
 		return NULL;
 
-	empty = alloc_empty_sheaf(s, GFP_NOWAIT);
+	empty = alloc_empty_sheaf(s, GFP_NOWAIT, SLAB_ALLOC_DEFAULT);
 	if (empty)
 		goto got_empty;
 
@@ -6074,7 +6073,7 @@ bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj)
 
 		local_unlock(&s->cpu_sheaves->lock);
 
-		empty = alloc_empty_sheaf(s, GFP_NOWAIT);
+		empty = alloc_empty_sheaf(s, GFP_NOWAIT, SLAB_ALLOC_DEFAULT);
 
 		if (!empty)
 			goto fail;
@@ -7619,7 +7618,7 @@ static int init_percpu_sheaves(struct kmem_cache *s)
 		if (!s->sheaf_capacity)
 			pcs->main = &bootstrap_sheaf;
 		else
-			pcs->main = alloc_empty_sheaf(s, GFP_KERNEL);
+			pcs->main = alloc_empty_sheaf(s, GFP_KERNEL, SLAB_ALLOC_DEFAULT);
 
 		if (!pcs->main)
 			return -ENOMEM;
@@ -8485,7 +8484,8 @@ static void __init bootstrap_cache_sheaves(struct kmem_cache *s)
 
 		pcs = per_cpu_ptr(s->cpu_sheaves, cpu);
 
-		pcs->main = __alloc_empty_sheaf(s, GFP_KERNEL, capacity);
+		pcs->main = __alloc_empty_sheaf(s, GFP_KERNEL,
+				SLAB_ALLOC_DEFAULT, capacity);
 
 		if (!pcs->main) {
 			failed = true;

-- 
2.54.0

[PATCH RFC 15/15] mm: remove the __GFP_NO_OBJ_EXT flag

[Vlastimil Babka (SUSE)]

All users of the flag are converted to SLAB_ALLOC_NO_RECURSE. Free up
the flag bit.

Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
---
 include/linux/gfp_types.h       |  7 -------
 include/linux/slab.h            |  2 +-
 include/trace/events/mmflags.h  | 10 +---------
 lib/alloc_tag.c                 |  2 +-
 tools/include/linux/gfp_types.h |  7 -------
 5 files changed, 3 insertions(+), 25 deletions(-)

diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h
index 6c75df30a281..a93b8bd200b7 100644
--- a/include/linux/gfp_types.h
+++ b/include/linux/gfp_types.h
@@ -55,7 +55,6 @@ enum {
 #ifdef CONFIG_LOCKDEP
 	___GFP_NOLOCKDEP_BIT,
 #endif
-	___GFP_NO_OBJ_EXT_BIT,
 	___GFP_LAST_BIT
 };
 
@@ -96,7 +95,6 @@ enum {
 #else
 #define ___GFP_NOLOCKDEP	0
 #endif
-#define ___GFP_NO_OBJ_EXT       BIT(___GFP_NO_OBJ_EXT_BIT)
 
 /*
  * Physical address zone modifiers (see linux/mmzone.h - low four bits)
@@ -137,17 +135,12 @@ enum {
  * node with no fallbacks or placement policy enforcements.
  *
  * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
- *
- * %__GFP_NO_OBJ_EXT causes slab allocation to have no object extension.
- * mark_obj_codetag_empty() should be called upon freeing for objects allocated
- * with this flag to indicate that their NULL tags are expected and normal.
  */
 #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)
 #define __GFP_ACCOUNT	((__force gfp_t)___GFP_ACCOUNT)
-#define __GFP_NO_OBJ_EXT   ((__force gfp_t)___GFP_NO_OBJ_EXT)
 
 /**
  * DOC: Watermark modifiers
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 11e82fdbe8d3..15d1917b81d3 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -1043,7 +1043,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
 /**
  * kmalloc_nolock - Allocate an object of given size from any context.
  * @size: size to allocate
- * @gfp_flags: GFP flags. Only __GFP_ACCOUNT, __GFP_ZERO, __GFP_NO_OBJ_EXT
+ * @gfp_flags: GFP flags. Only __GFP_ACCOUNT, __GFP_ZERO
  * allowed.
  * @node: node number of the target node.
  *
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index a6e5a44c9b42..c1a05ff0feab 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -54,18 +54,10 @@
 # define TRACE_GFP_FLAGS_LOCKDEP
 #endif
 
-#ifdef CONFIG_SLAB_OBJ_EXT
-# define TRACE_GFP_FLAGS_SLAB			\
-	TRACE_GFP_EM(NO_OBJ_EXT)
-#else
-# define TRACE_GFP_FLAGS_SLAB
-#endif
-
 #define TRACE_GFP_FLAGS				\
 	TRACE_GFP_FLAGS_GENERAL			\
 	TRACE_GFP_FLAGS_KASAN			\
-	TRACE_GFP_FLAGS_LOCKDEP			\
-	TRACE_GFP_FLAGS_SLAB
+	TRACE_GFP_FLAGS_LOCKDEP
 
 #undef TRACE_GFP_EM
 #define TRACE_GFP_EM(a) TRACE_DEFINE_ENUM(___GFP_##a##_BIT);
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index ed1bdcf1f8ab..63686b44a23d 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -776,7 +776,7 @@ static __init bool need_page_alloc_tagging(void)
  * If insufficient, a warning will be triggered to alert the user.
  *
  * TODO: Replace fixed-size array with dynamic allocation using
- * a GFP flag similar to ___GFP_NO_OBJ_EXT to avoid recursion.
+ * something similar to slab's SLAB_ALLOC_NO_RECURSE to avoid recursion.
  */
 #define EARLY_ALLOC_PFN_MAX		8192
 
diff --git a/tools/include/linux/gfp_types.h b/tools/include/linux/gfp_types.h
index 6c75df30a281..a93b8bd200b7 100644
--- a/tools/include/linux/gfp_types.h
+++ b/tools/include/linux/gfp_types.h
@@ -55,7 +55,6 @@ enum {
 #ifdef CONFIG_LOCKDEP
 	___GFP_NOLOCKDEP_BIT,
 #endif
-	___GFP_NO_OBJ_EXT_BIT,
 	___GFP_LAST_BIT
 };
 
@@ -96,7 +95,6 @@ enum {
 #else
 #define ___GFP_NOLOCKDEP	0
 #endif
-#define ___GFP_NO_OBJ_EXT       BIT(___GFP_NO_OBJ_EXT_BIT)
 
 /*
  * Physical address zone modifiers (see linux/mmzone.h - low four bits)
@@ -137,17 +135,12 @@ enum {
  * node with no fallbacks or placement policy enforcements.
  *
  * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg.
- *
- * %__GFP_NO_OBJ_EXT causes slab allocation to have no object extension.
- * mark_obj_codetag_empty() should be called upon freeing for objects allocated
- * with this flag to indicate that their NULL tags are expected and normal.
  */
 #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)
 #define __GFP_ACCOUNT	((__force gfp_t)___GFP_ACCOUNT)
-#define __GFP_NO_OBJ_EXT   ((__force gfp_t)___GFP_NO_OBJ_EXT)
 
 /**
  * DOC: Watermark modifiers

-- 
2.54.0

Re: [PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context

[Usama Arif]

On Tue, 09 Jun 2026 11:17:45 +0200 "Vlastimil Babka (SUSE)" <vbabka@kernel.org> wrote:

> This series is based on slab/for-next. If all goes well, it would
> hopefully go to slab/for-next soon after the 7.2 merge window, so any
> other work can be based on it to avoid conflicts, as it touches a lot
> parts of slab.
> 
> Git: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slab_alloc_flags
> 
> The slab implementation currently relies on gfp flags to convey
> some context information internally:
> 
> - The absence of both __GFP_RECLAIM flags is interpreted as "cannot spin
>   on locks", and intended to be used by kmalloc_nolock(). But false
>   positives are possible e.g. during early boot where gfp_allowed_mask
>   clears __GFP_RECLAIM from all allocations. This leads to unnecessary
>   allocation failures and workarounds such as fd3634312a04 ("debugobject:
>   Make it work with deferred page initialization - again").
> 
> - __GFP_NO_OBJ_EXT exists and takes up valuable bit in the gfp flags
>   space, only to prevent recursive kmalloc() allocations for obj_ext
>   arrays and sheaves.
> 

Hello Valstimil!

I think memory allocation profiling uses __GFP_NO_OBJ_EXT, and I dont see
it being removed in the series (hopefully I didnt miss it).

Adding Hao Ge in CC who did this in the commit:
mm/alloc_tag: replace fixed-size early PFN array with dynamic linked list


> The page allocator uses its internal alloc_flags to convey various
> context information, including ALLOC_TRYLOCK (meaning "cannot spin").
> This series copies that concept for the slab allocator, with its own
> slab-specific internal flags:
> 
> - SLAB_ALLOC_DEFAULT - no extra flags (the value is 0), but explicit
> - SLAB_ALLOC_TRYLOCK - do not spin on locks (used by kmalloc_nolock())
> - SLAB_ALLOC_NEW_SLAB - replacing existing 'bool new_slab' parameter
> 			for allocating obj_ext arrays
> - SLAB_ALLOC_NO_RECURSE - replacing usage of __GFP_NO_OBJ_EXT
> 
> To reduce the amount of parameters in various internal functions, we
> additionally introduce slab_alloc_context (also inspired by page
> allocator's alloc_context) for passing a number of existing arguments
> and the new alloc_flags:
> 
> /* Structure holding extra parameters for slab allocations */
> struct slab_alloc_context {
> 	unsigned long caller_addr;
> 	unsigned long orig_size;
> 	unsigned int alloc_flags;
> 	struct list_lru *lru;
> };
> 
> This also replaces the existing struct partial_context.
> 
> The last necessary piece is kmalloc_flags() which can take the
> alloc_flags in addition to gfp flags and is intended for the recursive
> allocations of sheaves and obj_ext arrays, so that both
> SLAB_ALLOC_TRYLOCK and SLAB_ALLOC_NO_RECURSE can be communicated.
> Internally it decides between kmalloc_nolock() and normal kmalloc()
> depending SLAB_ALLOC_TRYLOCK.
> 
> The rest of the series is gradually expanding the usage of both
> alloc_flags and slab_alloc_context as necessary, with bits of
> refactoring. Then, __GFP_NO_OBJ_EXT is removed completely.
> 
> Note that some usage of gfpflags_allow_spinning() relying on absence of
> __GFP_RECLAIM remains outside of slab (and page allocator) in memcg,
> page_owner and stackdepot code. These can thus yield false-positive
> decisions that spinning is not allowed, but should not result in
> important allocations failing anymore.
> 
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
> Vlastimil Babka (SUSE) (15):
>       mm/slab: always zero only requested size on alloc
>       mm/slab: stop inlining __slab_alloc_node()
>       mm/slab: introduce slab_alloc_context
>       mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK
>       mm/slab: add alloc_flags to slab_alloc_context
>       mm/slab: replace struct partial_context with slab_alloc_context
>       mm/slab: pass alloc_flags to new slab allocation
>       mm/slab: pass alloc_flags through slab_post_alloc_hook() chain
>       mm/slab: replace slab_alloc_node() parameters with slab_alloc_context
>       mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags
>       mm/slab: pass slab_alloc_context to __do_kmalloc_node()
>       mm/slab: introduce kmalloc_flags()
>       mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts()
>       mm/slab: replace __GFP_NO_OBJ_EXT with SLAB_ALLOC_NO_RECURSE for sheaves
>       mm: remove the __GFP_NO_OBJ_EXT flag
> 
>  include/linux/gfp_types.h       |   7 -
>  include/linux/slab.h            |  14 +-
>  include/trace/events/mmflags.h  |  10 +-
>  lib/alloc_tag.c                 |   2 +-
>  mm/kfence/core.c                |   6 +-
>  mm/memcontrol.c                 |   5 +-
>  mm/slab.h                       |  16 +-
>  mm/slub.c                       | 423 ++++++++++++++++++++++++----------------
>  tools/include/linux/gfp_types.h |   7 -
>  9 files changed, 288 insertions(+), 202 deletions(-)
> ---
> base-commit: 500b2c9755301742bdbb61249511ac11a4665dae
> change-id: 20260601-slab_alloc_flags-25c782b0c57c
> 
> Best regards,
> --  
> Vlastimil Babka (SUSE) <vbabka@kernel.org>
> 
> 

Re: [PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context

[Vlastimil Babka (SUSE)]

On 6/9/26 15:35, Usama Arif wrote:
> On Tue, 09 Jun 2026 11:17:45 +0200 "Vlastimil Babka (SUSE)" <vbabka@kernel.org> wrote:
> 
>> This series is based on slab/for-next. If all goes well, it would
>> hopefully go to slab/for-next soon after the 7.2 merge window, so any
>> other work can be based on it to avoid conflicts, as it touches a lot
>> parts of slab.
>> 
>> Git: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slab_alloc_flags
>> 
>> The slab implementation currently relies on gfp flags to convey
>> some context information internally:
>> 
>> - The absence of both __GFP_RECLAIM flags is interpreted as "cannot spin
>>   on locks", and intended to be used by kmalloc_nolock(). But false
>>   positives are possible e.g. during early boot where gfp_allowed_mask
>>   clears __GFP_RECLAIM from all allocations. This leads to unnecessary
>>   allocation failures and workarounds such as fd3634312a04 ("debugobject:
>>   Make it work with deferred page initialization - again").
>> 
>> - __GFP_NO_OBJ_EXT exists and takes up valuable bit in the gfp flags
>>   space, only to prevent recursive kmalloc() allocations for obj_ext
>>   arrays and sheaves.
>> 
> 
> Hello Valstimil!
> 
> I think memory allocation profiling uses __GFP_NO_OBJ_EXT, and I dont see
> it being removed in the series (hopefully I didnt miss it).
> 
> Adding Hao Ge in CC who did this in the commit:
> mm/alloc_tag: replace fixed-size early PFN array with dynamic linked list

Thanks for the heads up. I missed it because my series is based on
slab/for-next and that commit is in mm-unstable. My patch 15 actually
modifies the TODO comment that is meanwhile resolved by Hao Ge's patch.

Which means my patch 15/15 can't be used as-is, and at worst I will drop it.
But I'd encourage Hao Ge with Suren to find some way to avoid the gfp flag
usage too, because it's now quite a niche use case (preventing false
positive CONFIG_MEM_ALLOC_PROFILING_DEBUG warnings, IIUC?) to take a
valuable gfp flag bit, IMHO.

>> The page allocator uses its internal alloc_flags to convey various
>> context information, including ALLOC_TRYLOCK (meaning "cannot spin").
>> This series copies that concept for the slab allocator, with its own
>> slab-specific internal flags:
>> 
>> - SLAB_ALLOC_DEFAULT - no extra flags (the value is 0), but explicit
>> - SLAB_ALLOC_TRYLOCK - do not spin on locks (used by kmalloc_nolock())
>> - SLAB_ALLOC_NEW_SLAB - replacing existing 'bool new_slab' parameter
>> 			for allocating obj_ext arrays
>> - SLAB_ALLOC_NO_RECURSE - replacing usage of __GFP_NO_OBJ_EXT
>> 
>> To reduce the amount of parameters in various internal functions, we
>> additionally introduce slab_alloc_context (also inspired by page
>> allocator's alloc_context) for passing a number of existing arguments
>> and the new alloc_flags:
>> 
>> /* Structure holding extra parameters for slab allocations */
>> struct slab_alloc_context {
>> 	unsigned long caller_addr;
>> 	unsigned long orig_size;
>> 	unsigned int alloc_flags;
>> 	struct list_lru *lru;
>> };
>> 
>> This also replaces the existing struct partial_context.
>> 
>> The last necessary piece is kmalloc_flags() which can take the
>> alloc_flags in addition to gfp flags and is intended for the recursive
>> allocations of sheaves and obj_ext arrays, so that both
>> SLAB_ALLOC_TRYLOCK and SLAB_ALLOC_NO_RECURSE can be communicated.
>> Internally it decides between kmalloc_nolock() and normal kmalloc()
>> depending SLAB_ALLOC_TRYLOCK.
>> 
>> The rest of the series is gradually expanding the usage of both
>> alloc_flags and slab_alloc_context as necessary, with bits of
>> refactoring. Then, __GFP_NO_OBJ_EXT is removed completely.
>> 
>> Note that some usage of gfpflags_allow_spinning() relying on absence of
>> __GFP_RECLAIM remains outside of slab (and page allocator) in memcg,
>> page_owner and stackdepot code. These can thus yield false-positive
>> decisions that spinning is not allowed, but should not result in
>> important allocations failing anymore.
>> 
>> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
>> ---
>> Vlastimil Babka (SUSE) (15):
>>       mm/slab: always zero only requested size on alloc
>>       mm/slab: stop inlining __slab_alloc_node()
>>       mm/slab: introduce slab_alloc_context
>>       mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK
>>       mm/slab: add alloc_flags to slab_alloc_context
>>       mm/slab: replace struct partial_context with slab_alloc_context
>>       mm/slab: pass alloc_flags to new slab allocation
>>       mm/slab: pass alloc_flags through slab_post_alloc_hook() chain
>>       mm/slab: replace slab_alloc_node() parameters with slab_alloc_context
>>       mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags
>>       mm/slab: pass slab_alloc_context to __do_kmalloc_node()
>>       mm/slab: introduce kmalloc_flags()
>>       mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts()
>>       mm/slab: replace __GFP_NO_OBJ_EXT with SLAB_ALLOC_NO_RECURSE for sheaves
>>       mm: remove the __GFP_NO_OBJ_EXT flag
>> 
>>  include/linux/gfp_types.h       |   7 -
>>  include/linux/slab.h            |  14 +-
>>  include/trace/events/mmflags.h  |  10 +-
>>  lib/alloc_tag.c                 |   2 +-
>>  mm/kfence/core.c                |   6 +-
>>  mm/memcontrol.c                 |   5 +-
>>  mm/slab.h                       |  16 +-
>>  mm/slub.c                       | 423 ++++++++++++++++++++++++----------------
>>  tools/include/linux/gfp_types.h |   7 -
>>  9 files changed, 288 insertions(+), 202 deletions(-)
>> ---
>> base-commit: 500b2c9755301742bdbb61249511ac11a4665dae
>> change-id: 20260601-slab_alloc_flags-25c782b0c57c
>> 
>> Best regards,
>> --  
>> Vlastimil Babka (SUSE) <vbabka@kernel.org>
>> 
>> 

Re: [PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context

[Alexei Starovoitov]

On Tue Jun 9, 2026 at 2:17 AM PDT, Vlastimil Babka (SUSE) wrote:
> This series is based on slab/for-next. If all goes well, it would
> hopefully go to slab/for-next soon after the 7.2 merge window, so any
> other work can be based on it to avoid conflicts, as it touches a lot
> parts of slab.
>
> Git: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slab_alloc_flags

Overall looks great to me.
I would ship all patches except the last one for this merge window,
since I don't see anything controversial or dangerous in there.
Especially since it touches slab so much. My slab-arena changes
would need to adopt it and I don't want to delay the whole thing by two merge windows.
Harry's changes would need to rebased as well.
So the sooner the trees converge the better.