Commit e593b2bf authored Jan 23, 2017 by Amir Goldstein Committed by Miklos Szeredi Feb 07, 2017

ovl: properly implement sync_filesystem()



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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent 01ad3eb8

fs/overlayfs/super.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -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,