question: The use of s_op->write_super_lockfs/unlockfs

[OHKUBO Katsuhiko]

Hello.

There ars
	void write_super_lockfs(super_block *)
	void unlockfs(super_block *)
in struct super_operations.

Ext3 and reiserfs have implementations of it.
But I cannot find callers of it and system calls for it.

There are some pathches such as 
	http://www.lifix.fi/listarchive/lkml/2001-08/msg00464.html
but it's not included in Linux 2.4.18/2.5.21.
	drivers/md/lvm.c has only callers of functions in this patch
	if defined LVM_VFS_ENHANCEMENT, but there aren't function bodys.

Q1: Who does use s_op->write_super_lockfs/unlockfs now?
Q2: How lockfs/unlockfs will be used in future?
Q3: Is it enable to implement of system calls for lockfs/unlockfs
	without deadlocks?

Thanks in advance.

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OHKUBO Katsuhiko [e-mail]