xfs: check xfs_buf_read_uncached returns correctly

xfs_buf_read_uncached() has two failure modes. If can either return
NULL or bp->b_error != 0 depending on the type of failure, and not
all callers check for both. Fix it so that xfs_buf_read_uncached()
always returns the error status, and the buffer is returned as a
function parameter. The buffer will only be returned on success.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index d99ec8335750..6fbcbbfb4d1a 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -688,29 +688,39 @@ xfs_buf_readahead_map(
  * Read an uncached buffer from disk. Allocates and returns a locked
  * buffer containing the disk contents or nothing.
  */
-struct xfs_buf *
+int
 xfs_buf_read_uncached(
         struct xfs_buftarg      *target,
         xfs_daddr_t             daddr,
         size_t                  numblks,
         int                     flags,
+        struct xfs_buf          **bpp,
         const struct xfs_buf_ops *ops)
 {
         struct xfs_buf          *bp;
 
+        *bpp = NULL;
+
         bp = xfs_buf_get_uncached(target, numblks, flags);
         if (!bp)
-                return NULL;
+                return -ENOMEM;
 
         /* set up the buffer for a read IO */
         ASSERT(bp->b_map_count == 1);
-        bp->b_bn = daddr;
+        bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
         bp->b_maps[0].bm_bn = daddr;
         bp->b_flags |= XBF_READ;
         bp->b_ops = ops;
 
         xfs_buf_submit_wait(bp);
-        return bp;
+        if (bp->b_error) {
+                int     error = bp->b_error;
+                xfs_buf_relse(bp);
+                return error;
+        }
+
+        *bpp = bp;
+        return 0;
 }
 
 /*