xfs: prevent extsize alignment from exceeding maximum extent size

When doing delayed allocation, if the allocation size is for a
maximally sized extent, extent size alignment can push it over this
limit. This results in an assert failure in xfs_bmbt_set_allf() as
the extent length is too large to find in the extent record.

Fix this by ensuring that we allow for space that extent size
alignment requires (up to 2 * (extsize -1) blocks as we have to
handle both head and tail alignment) when limiting the maximum size
of the extent.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index f3a3768189bb..3e9c278a8f78 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -4487,6 +4487,16 @@ xfs_bmapi(
                                 /* Figure out the extent size, adjust alen */
                                 extsz = xfs_get_extsz_hint(ip);
                                 if (extsz) {
+                                        /*
+                                         * make sure we don't exceed a single
+                                         * extent length when we align the
+                                         * extent by reducing length we are
+                                         * going to allocate by the maximum
+                                         * amount extent size aligment may
+                                         * require.
+                                         */
+                                        alen = XFS_FILBLKS_MIN(len,
+                                                   MAXEXTLEN - (2 * extsz - 1));
                                         error = xfs_bmap_extsize_align(mp,
                                                         &got, &prev, extsz,
                                                         rt, eof,