Josef Bacik
2012-Jul-20 20:08 UTC
[PATCH] Btrfs: don''t return true in releasepage unless we actually freed the eb
I noticed while looking at an extent_buffer race that we will
unconditionally return 1 if we get down to release_extent_buffer after
clearing the tree ref. However we can easily race in here and get a ref on
the eb and not actually free the eb. So make release_extent_buffer return 1
if it free''d the eb and 0 if not so we can be a little kinder to the
vm.
Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
fs/btrfs/extent_io.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 7926e1e..b778fc2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4319,7 +4319,7 @@ static inline void btrfs_release_extent_buffer_rcu(struct
rcu_head *head)
}
/* Expects to have eb->eb_lock already held */
-static void release_extent_buffer(struct extent_buffer *eb, gfp_t mask)
+static int release_extent_buffer(struct extent_buffer *eb, gfp_t mask)
{
WARN_ON(atomic_read(&eb->refs) == 0);
if (atomic_dec_and_test(&eb->refs)) {
@@ -4340,9 +4340,11 @@ static void release_extent_buffer(struct extent_buffer
*eb, gfp_t mask)
btrfs_release_extent_buffer_page(eb, 0);
call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
- return;
+ return 1;
}
spin_unlock(&eb->refs_lock);
+
+ return 0;
}
void free_extent_buffer(struct extent_buffer *eb)
@@ -4981,7 +4983,6 @@ int try_release_extent_buffer(struct page *page, gfp_t
mask)
spin_unlock(&eb->refs_lock);
return 0;
}
- release_extent_buffer(eb, mask);
- return 1;
+ return release_extent_buffer(eb, mask);
}
--
1.7.7.6
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