The patch titled
Subject: shmem: skip page split if we're not reclaiming
has been added to the -mm mm-unstable branch. Its filename is
shmem-skip-page-split-if-were-not-reclaiming.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/shmem-skip-page-split-if-were-not-reclaiming.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Subject: shmem: skip page split if we're not reclaiming
Date: Thu, 9 Mar 2023 15:05:43 -0800
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@xxxxxxxxxx
Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
---
--- a/mm/shmem.c~shmem-skip-page-split-if-were-not-reclaiming
+++ a/mm/shmem.c
@@ -1332,6 +1332,12 @@ static int shmem_writepage(struct page *
if (WARN_ON_ONCE(!wbc->for_reclaim))
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
* "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
@@ -1347,10 +1353,6 @@ static int shmem_writepage(struct page *
}
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
_
Patches currently in -mm which might be from mcgrof@xxxxxxxxxx are
shmem-remove-check-for-folio-lock-on-writepage.patch
shmem-set-shmem_writepage-variables-early.patch
shmem-move-reclaim-check-early-on-writepages.patch
shmem-skip-page-split-if-were-not-reclaiming.patch
shmem-update-documentation.patch
shmem-add-support-to-ignore-swap.patch
