[RFC][PATCH v2 2/3] ovl: properly implement sync_filesystem()
From: Amir Goldstein <amir73il@gmail.com>
Date: 2017-01-23 12:33:12
Also in:
linux-fsdevel
Subsystem:
filesystems (vfs and infrastructure), overlay filesystem, the rest · Maintainers:
Alexander Viro, Christian Brauner, Miklos Szeredi, Amir Goldstein, Linus Torvalds
overlayfs syncs all inode pages on sync_filesystem(), but it also
needs to call s_op->sync_fs() of upper fs for metadata sync.
This fixes correctness of syncfs(2) as demonstrated by following
xfs specific test:
xfs_sync_stats()
{
echo $1
echo -n "xfs_log_force = "
grep log /proc/fs/xfs/stat | awk '{ print $5 }'
}
xfs_sync_stats "before touch"
touch x
xfs_sync_stats "after touch"
xfs_io -c syncfs .
xfs_sync_stats "after syncfs"
xfs_io -c fsync x
xfs_sync_stats "after fsync"
xfs_io -c fsync x
xfs_sync_stats "after fsync #2"
When this test is run in overlay mount over xfs, log force
count does not increase with syncfs command.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/super.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6792bb7..346f668 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c@@ -160,6 +160,25 @@ static void ovl_put_super(struct super_block *sb) kfree(ufs); } +static int ovl_sync_fs(struct super_block *sb, int wait) +{ + struct ovl_fs *ufs = sb->s_fs_info; + struct super_block *upper_sb; + int ret; + + if (!ufs->upper_mnt) + return 0; + upper_sb = ufs->upper_mnt->mnt_sb; + if (!upper_sb->s_op->sync_fs) + return 0; + + /* real inodes have already been synced by sync_filesystem(ovl_sb) */ + down_read(&upper_sb->s_umount); + ret = upper_sb->s_op->sync_fs(upper_sb, wait); + up_read(&upper_sb->s_umount); + return ret; +} + /** * ovl_statfs * @sb: The overlayfs super block
@@ -222,6 +241,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data) static const struct super_operations ovl_super_operations = { .put_super = ovl_put_super, + .sync_fs = ovl_sync_fs, .statfs = ovl_statfs, .show_options = ovl_show_options, .remount_fs = ovl_remount,
--
2.7.4