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Btrfs: don't return true in releasepage unless we actually freed the eb

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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>
This commit is contained in:
Josef Bacik 2012-07-20 16:05:36 -04:00 committed by Chris Mason
parent a98cdb85b9
commit e64860aa05
1 changed files with 5 additions and 4 deletions
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9
fs/btrfs/extent_io.c
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@ -4300,7 +4300,7 @@ 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)) {
@ -4321,9 +4321,11 @@ 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)
@ -4962,7 +4964,6 @@ 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);
}