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>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index f08206f..e6243f7 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4300,7 +4300,7 @@
}
/* 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 @@
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 @@
spin_unlock(&eb->refs_lock);
return 0;
}
- release_extent_buffer(eb, mask);
- return 1;
+ return release_extent_buffer(eb, mask);
}