xfs: don't verify buffers after IO errors

When we read a buffer, we might get an error from the underlying
block device and not the real data. Hence if we get an IO error, we
shouldn't run the verifier but instead just pass the IO error
straight through.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NMark Tinguely <tinguely@sgi.com>
Signed-off-by: NBen Myers <bpm@sgi.com>

fs/xfs/xfs_buf.c

@@ -1022,7 +1022,9 @@ xfs_buf_iodone_work(
 	bool			read = !!(bp->b_flags & XBF_READ);
 
 	bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
-	if (read && bp->b_ops)
+
+	/* only validate buffers that were read without errors */
+	if (read && bp->b_ops && !bp->b_error && (bp->b_flags & XBF_DONE))
 		bp->b_ops->verify_read(bp);
 
 	if (bp->b_iodone)