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authorJohannes Weiner <hannes@cmpxchg.org>2014-04-03 14:47:41 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-21 09:23:06 -0800
commitc2667299f23105ae24c019699b46022a1701ff0e (patch)
tree1f06d02f03eb0c2cc2587935d5dc79db99b9294a
parentd35a6232f850723d46c3d9271a6b6217af58731b (diff)
mm: shmem: save one radix tree lookup when truncating swapped pages
commit 6dbaf22ce1f1dfba33313198eb5bd989ae76dd87 upstream. Page cache radix tree slots are usually stabilized by the page lock, but shmem's swap cookies have no such thing. Because the overall truncation loop is lockless, the swap entry is currently confirmed by a tree lookup and then deleted by another tree lookup under the same tree lock region. Use radix_tree_delete_item() instead, which does the verification and deletion with only one lookup. This also allows removing the delete-only special case from shmem_radix_tree_replace(). Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Greg Thelen <gthelen@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jan Kara <jack@suse.cz> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Luigi Semenzato <semenzato@google.com> Cc: Metin Doslu <metin@citusdata.com> Cc: Michel Lespinasse <walken@google.com> Cc: Ozgun Erdogan <ozgun@citusdata.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Roman Gushchin <klamm@yandex-team.ru> Cc: Ryan Mallon <rmallon@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/shmem.c25
1 files changed, 12 insertions, 13 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index f0d698ba7d0f..27ab68c54f32 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -243,19 +243,17 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
pgoff_t index, void *expected, void *replacement)
{
void **pslot;
- void *item = NULL;
+ void *item;
VM_BUG_ON(!expected);
+ VM_BUG_ON(!replacement);
pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
- if (pslot)
- item = radix_tree_deref_slot_protected(pslot,
- &mapping->tree_lock);
+ if (!pslot)
+ return -ENOENT;
+ item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock);
if (item != expected)
return -ENOENT;
- if (replacement)
- radix_tree_replace_slot(pslot, replacement);
- else
- radix_tree_delete(&mapping->page_tree, index);
+ radix_tree_replace_slot(pslot, replacement);
return 0;
}
@@ -387,14 +385,15 @@ export:
static int shmem_free_swap(struct address_space *mapping,
pgoff_t index, void *radswap)
{
- int error;
+ void *old;
spin_lock_irq(&mapping->tree_lock);
- error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
+ old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
spin_unlock_irq(&mapping->tree_lock);
- if (!error)
- free_swap_and_cache(radix_to_swp_entry(radswap));
- return error;
+ if (old != radswap)
+ return -ENOENT;
+ free_swap_and_cache(radix_to_swp_entry(radswap));
+ return 0;
}
/*