xfs: only bother with sync_filesystem during readonly remount

mainline inclusion
from mainline-v5.16-rc3
commit b97cca3b
category: bugfix
bugzilla: 187526,https://gitee.com/openeuler/kernel/issues/I4KIAO

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b97cca3ba9098522e5a1c3388764ead42640c1a5



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In commit 02b9984d, we pushed a sync_filesystem() call from the VFS
into xfs_fs_remount.  The only time that we ever need to push dirty file
data or metadata to disk for a remount is if we're remounting the
filesystem read only, so this really could be moved to xfs_remount_ro.

Once we've moved the call site, actually check the return value from
sync_filesystem.

Fixes: 02b9984d ("fs: push sync_filesystem() down to the file system's remount_fs()")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>