[PATCH 3/9] xfs_copy: actually do directio writes to block devices

Darrick J. Wong
2023-11-22T23:07:09Z

From: Darrick J. Wong <djwong@kernel.org>

Not sure why block device targets don't get O_DIRECT in !buffered mode,
but it's misleading when the copy completes instantly only to stall
forever due to fsync-on-close. Adjust the "write last sector" code to
allocate a properly aligned buffer.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
copy/xfs_copy.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/copy/xfs_copy.c b/copy/xfs_copy.c
index 79f65946709..26de6b2ee1c 100644
--- a/copy/xfs_copy.c
+++ b/copy/xfs_copy.c
@@ -854,6 +854,8 @@ main(int argc, char **argv)
progname, target[i].name, progname);
exit(1);
}
+ if (!buffered_output)
+ open_flags |= O_DIRECT;
}

target[i].fd = open(target[i].name, open_flags, 0644);
@@ -887,20 +889,22 @@ main(int argc, char **argv)
}
}
} else {
- char *lb[XFS_MAX_SECTORSIZE] = { NULL };
+ char *lb = memalign(wbuf_align, XFS_MAX_SECTORSIZE);
off64_t off;

/* ensure device files are sufficiently large */
+ memset(lb, 0, XFS_MAX_SECTORSIZE);

off = mp->m_sb.sb_dblocks * source_blocksize;
- off -= sizeof(lb);
- if (pwrite(target[i].fd, lb, sizeof(lb), off) < 0) {
+ off -= XFS_MAX_SECTORSIZE;
+ if (pwrite(target[i].fd, lb, XFS_MAX_SECTORSIZE, off) < 0) {
do_log(_("%s: failed to write last block\n"),
progname);
do_log(_("\tIs target \"%s\" too small?\n"),
target[i].name);
die_perror();
}
+ free(lb);
}
}