The patch titled Subject: mm: kmem: drop __GFP_NOFAIL when allocating objcg vectors has been added to the -mm mm-hotfixes-unstable branch. Its filename is cgroups-warning-for-metadata-allocation-with-gfp_nofail-was-re-folio_alloc_buffers-doing-allocations-order-1-with-gfp_nofail.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Roman Gushchin roman.gushchin@linux.dev Subject: mm: kmem: drop __GFP_NOFAIL when allocating objcg vectors Date: Tue, 7 Nov 2023 09:18:02 -0800

Objcg vectors attached to slab pages to store slab object ownership information are allocated using gfp flags for the original slab allocation. Depending on slab page order and the size of slab objects, objcg vector can take several pages.

If the original allocation was done with the __GFP_NOFAIL flag, it triggered a warning in the page allocation code. Indeed, order > 1 pages should not been allocated with the __GFP_NOFAIL flag.

Fix this by simply dropping the __GFP_NOFAIL flag when allocating the objcg vector. It effectively allows to skip the accounting of a single slab object under a heavy memory pressure.

An alternative would be to implement the mechanism to fallback to order-0 allocations for accounting metadata, which is also not perfect because it will increase performance penalty and memory footprint of the kernel memory accounting under memory pressure.

Link: https://lkml.kernel.org/r/ZUp8ZFGxwmCx4ZFr@P9FQF9L96D.corp.robot.car Signed-off-by: Roman Gushchin roman.gushchin@linux.dev Reported-by: Christoph Lameter cl@linux.com Closes: https://lkml.kernel.org/r/6b42243e-f197-600a-5d22-56bd728a5ad8@gentwo.org Acked-by: Shakeel Butt shakeelb@google.com Cc: Matthew Wilcox willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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

--- a/mm/memcontrol.c~cgroups-warning-for-metadata-allocation-with-gfp_nofail-was-re-folio_alloc_buffers-doing-allocations-order-1-with-gfp_nofail +++ a/mm/memcontrol.c @@ -2936,7 +2936,8 @@ void mem_cgroup_commit_charge(struct fol * Moreover, it should not come from DMA buffer and is not readily * reclaimable. So those GFP bits should be masked off. */ -#define OBJCGS_CLEAR_MASK (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT) +#define OBJCGS_CLEAR_MASK (__GFP_DMA | __GFP_RECLAIMABLE | \ + __GFP_ACCOUNT | __GFP_NOFAIL)

/* * mod_objcg_mlstate() may be called with irq enabled, so _

Patches currently in -mm which might be from roman.gushchin@linux.dev are

cgroups-warning-for-metadata-allocation-with-gfp_nofail-was-re-folio_alloc_buffers-doing-allocations-order-1-with-gfp_nofail.patch