xfs: account for null transactions in bunmapi

In e1a4e37cc7b665 ("xfs: try to avoid blowing out the transaction
reservation when bunmaping a shared extent"), we try to constrain the
amount of real extents we unmap from the data fork in a given call so
that we don't blow out transaction reservations.

However, not all bunmapi operations require a transaction -- if we're
only removing a delalloc extent, no transaction is needed, so we have to
code against that.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 1210f684d3c28f9af8d8403c1f0222ef06dc380b..1bddbba6b80c960bdcc10c9a30210c119e1b2f77 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5136,7 +5136,7 @@ __xfs_bunmapi(
         * blowing out the transaction with a mix of EFIs and reflink
         * adjustments.
         */
-       if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK)
+       if (tp && xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK)
                max_len = min(len, xfs_refcount_max_unmap(tp->t_log_res));
        else
                max_len = len;