[PATCH 5/3] xfs: limit specualtive delalloc to maxioffset

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

Speculative delayed allocation beyond EOF near the maximum supported
file offset can result in creating delalloc extents beyond
mp->m_maxioffset (8EB). These can never be trimmed during
xfs_free_eof_blocks() because they are beyond mp->m_maxioffset, and
that results in assert failures in xfs_fs_destroy_inode() due to
delalloc blocks still being present. xfstests 071 exposes this
problem.

Limit speculative delalloc to mp->m_maxioffset to avoid this
problem.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_iomap.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 303c03a..4a08ea3 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -412,6 +412,15 @@ retry:
 			return error;
 	}
 
+	/*
+	 * Make sure preallocation does not create extents beyond the range we
+	 * actually support in this filesystem.
+	 */
+	if (last_fsb > XFS_B_TO_FSB(mp, mp->m_maxioffset))
+		last_fsb = XFS_B_TO_FSB(mp, mp->m_maxioffset);
+
+	ASSERT(last_fsb > offset_fsb);
+
 	nimaps = XFS_WRITE_IMAPS;
 	error = xfs_bmapi_delay(ip, offset_fsb, last_fsb - offset_fsb,
 				imap, &nimaps, XFS_BMAPI_ENTIRE);

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