Btrfs: handle no memory properly in prepare_pages

Instead of doing a BUG_ON(1) in prepare_pages if grab_cache_page() fails, just
loop through the pages we've already grabbed and unlock and release them, then
return -ENOMEM like we should.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 65b2424a411..9e097fbfc78 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -792,8 +792,12 @@ again:
         for (i = 0; i < num_pages; i++) {
                 pages[i] = grab_cache_page(inode->i_mapping, index + i);
                 if (!pages[i]) {
-                        err = -ENOMEM;
-                        BUG_ON(1);
+                        int c;
+                        for (c = i - 1; c >= 0; c--) {
+                                unlock_page(pages[c]);
+                                page_cache_release(pages[c]);
+                        }
+                        return -ENOMEM;
                 }
                 wait_on_page_writeback(pages[i]);
         }