mm/slab, ipc: kmem_buckets kernel-doc and msg_msg accounting fixes

Hi!

As Vlastimil suggested[1], these are the first two patches of v6, split out for 7.4. The rest of the skb buckets series will come back for 7.5.

2/2 now keeps SLAB_ACCOUNT on the msg_msg bucket caches and allocates with GFP_KERNEL_ACCOUNT as well, so a msg_msg is charged with CONFIG_SLAB_BUCKETS either way.

Thanks!

-Kees

v7:
- split v6's 1/8 and 2/8 out for 7.4; 3/8 to 8/8 will return for 7.5 (Vlastimil)
- 2/2: keep SLAB_ACCOUNT in kmem_buckets_create(), and add Cc: stable (Vlastimil, Andrew, Harry)
v6: https://lore.kernel.org/all/[email protected]/
v5: https://lore.kernel.org/all/[email protected]/
v4: https://lore.kernel.org/all/[email protected]/
v3: https://lore.kernel.org/all/[email protected]/

[1] https://lore.kernel.org/all/[email protected]/

Kees Cook (2):
mm/slab: Mark the kmem_buckets_create() context as a Context: section ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again

 ipc/msgutil.c    | 3 ++-
 mm/slab_common.c | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

2.55.0

kmem_buckets_create() had the same sentence about calling context as kmem_cache_create(), but lacked the "Context:" prefix, so kernel-doc rendered in the body instead of as a "context" section.

Give it the missing prefix. Additionally fix the "a interrupt" typo __kmem_cache_create_args() had.

---
 mm/slab_common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index b19ba1b31484..270408ce5a9d 100644
@@ -311,7 +311,7 @@ __kmem_cache_alias(const char *name, unsigned int size, slab_flags_t flags,
  * &SLAB_TYPESAFE_BY_RCU - Slab page (not individual objects) freeing delayed
  * by a grace period - see the full description before using.
  *
- * Context: Cannot be called within a interrupt, but can be interrupted.
+ * Context: Cannot be called within an interrupt, but can be interrupted.
  *
  * Return: a pointer to the cache on success, NULL on failure.
  */

@@ -422,7 +422,7 @@ static struct kmem_cache *kmem_buckets_cache __ro_after_init;
  *		to/from userspace.
  * @ctor: A constructor for the objects, run when new allocations are made.
  *
- * Cannot be called within an interrupt, but can be interrupted.
+ * Context: Cannot be called within an interrupt, but can be interrupted.
  *
  * Return: a pointer to the cache on success, NULL on failure. When
  * CONFIG_SLAB_BUCKETS is not enabled, ZERO_SIZE_PTR is returned, and

2.55.0

Since commit 734bbc1c97ea7 ("ipc, msg: Use dedicated slab buckets for alloc_msg()"), alloc_msg() allocates with GFP_KERNEL, and a msg_msg is accounted only through SLAB_ACCOUNT on its bucket caches. With CONFIG_SLAB_BUCKETS=n, kmem_buckets_create() creates no caches and kmem_buckets_alloc() is a GFP_KERNEL kmalloc() from the general caches, which do not account it; the same happens when kmem_buckets_create() fails. Either way, the allocation is not charged to the sender's memory cgroup.

Allocate with GFP_KERNEL_ACCOUNT again, as before that commit, so the allocation is charged whichever cache serves it.

Build tested ARCH=x86_64 defconfig with GCC 16.2.0, with CONFIG_SLAB_BUCKETS as y and n.

---
 ipc/msgutil.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index e28f0cecb2ec..12663a40e9ae 100644
@@ -58,7 +58,8 @@ static struct msg_msg *alloc_msg(size_t len)
 	size_t alen;
 
 	alen = min(len, DATALEN_MSG);
-	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen, GFP_KERNEL);
+	msg = kmem_buckets_alloc(msg_buckets, sizeof(*msg) + alen,
+				 GFP_KERNEL_ACCOUNT);
 	if (msg == NULL)
 		return NULL;
 

2.55.0

Looks good to me,

Thanks!

Applied to mm/slab.git slab/for-7.4/misc, thanks!

[1/2] mm/slab: Mark the kmem_buckets_create() context as a Context: section

      commit: 655668f0caf32a42fef10aaf31137e52f46a0260
[2/2] ipc, msg: Account msg_msg allocations with GFP_KERNEL_ACCOUNT again
      commit: 49c0b3dedf7c8c64e432e63dd7b24f00909916d8

Best regards,

Vlastimil Babka (SUSE) <[email protected]>