The for_each_perag_from() iteration macro relies on sb_agcount to process every perag currently within EOFS from a given starting point. It's perfectly valid to have perag structures beyond sb_agcount, however, such as if a growfs is in progress. If a perag loop happens to race with growfs in this manner, it will actually attempt to process the post-EOFS perag where ->pag_agno == sb_agcount. This is reproduced by xfs/104 and manifests as the following assert failure in superblock write verifier context: XFS: Assertion failed: agno < mp->m_sb.sb_agcount, file: fs/xfs/libxfs/xfs_types.c, line: 22 Update the corresponding macro to only process perags that are within the current sb_agcount. Fixes: 58d43a7e3263 ("xfs: pass perags around in fsmap data dev functions") Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org>