xfs: xfs_trans_read_buf() should return an error on failure

When inside a transaction and we fail to read a buffer,
xfs_trans_read_buf returns a null buffer pointer and no error.
xfs_do_da_buf() checks the error return, but not the buffer, and as
a result this read failure condition causes a panic when it attempts
to dereference the non-existant buffer.

Make xfs_trans_read_buf() return the same error for this situation
regardless of whether it is in a transaction or not. This means
every caller does not need to check both the error return and the
buffer before proceeding to use the buffer.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>

diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index 3bea66132334c91e83278a5c581fae7d399e1490..03b3b7f85a3b59b68a1d6ff99ba83ac38ac7094c 100644 (file)
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -383,7 +383,8 @@ xfs_trans_read_buf(
        bp = xfs_buf_read(target, blkno, len, flags | XBF_DONT_BLOCK);
        if (bp == NULL) {
                *bpp = NULL;
-               return 0;
+               return (flags & XBF_TRYLOCK) ?
+                                       0 : XFS_ERROR(ENOMEM);
        }
        if (XFS_BUF_GETERROR(bp) != 0) {
            XFS_BUF_SUPER_STALE(bp);