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shmem: skip page split if we're not reclaiming

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In theory when info->flags & VM_LOCKED we should not be getting
shem_writepage() called so we should be verifying this with a
WARN_ON_ONCE().  Since we should not be swapping then best to ensure we
also don't do the folio split earlier too.  So just move the check early
to avoid folio splits in case its a dubious call.

We also have a similar early bail when !total_swap_pages so just move that
earlier to avoid the possible folio split in the same situation.

Link: https://lkml.kernel.org/r/20230309230545.2930737-5-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Luis Chamberlain 2023-03-09 15:05:43 -08:00 • committed by Andrew Morton
parent cf7992bf61
commit 9a976f0c84
1 changed files with 6 additions and 4 deletions
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10
mm/shmem.c
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@ -1347,6 +1347,12 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
if (WARN_ON_ONCE(!wbc->for_reclaim)) if (WARN_ON_ONCE(!wbc->for_reclaim))
goto redirty; goto redirty;
if (WARN_ON_ONCE(info->flags & VM_LOCKED))
goto redirty;
if (!total_swap_pages)
goto redirty;
/* /*
* If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
* "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages, * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
@ -1362,10 +1368,6 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
} }
index = folio->index; index = folio->index;
if (info->flags & VM_LOCKED)
goto redirty;
if (!total_swap_pages)
goto redirty;
/* /*
* This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC