Btrfs: avoid NULL pointer deref in try_release_extent_buffer

If we fail to find a pointer in the radix tree, don't try
to deref the NULL one we do have.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index f60aa3c..143d3f5 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3837,8 +3837,10 @@ int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
 
        spin_lock(&tree->buffer_lock);
        eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
-       if (!eb)
-               goto out;
+       if (!eb) {
+               spin_unlock(&tree->buffer_lock);
+               return ret;
+       }
 
        if (test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
                ret = 0;