Btrfs: Change find_extent_buffer to use TestSetPageLocked

This makes it possible for callers to check for extent_buffers in cache
without deadlocking against any btree locks held.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index bd15cdcaba95..40a5f53cb040 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2808,10 +2808,15 @@ struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
                 goto lru_add;
 
         for (i = 0; i < num_pages; i++, index++) {
-                p = find_lock_page(mapping, index);
+                p = find_get_page(mapping, index);
                 if (!p) {
                         goto fail;
                 }
+                if (TestSetPageLocked(p)) {
+                        page_cache_release(p);
+                        goto fail;
+                }
+
                 set_page_extent_mapped(p);
                 mark_page_accessed(p);