linux-kernel - lock_rename for cluster filesystems? (was: Re: [PATCH] prune_icache

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Date:	Fri, 2 Mar 2007 22:07:40 -0500
From:	"Mike Snitzer" <snitzer@...il.com>
To:	"Wendy Cheng" <wcheng@...hat.com>
Cc:	"Russell Cattelan" <cattelan@...barn.com>,
	"Andrew Morton" <akpm@...l.org>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: lock_rename for cluster filesystems? (was: Re: [PATCH] prune_icache_sb)

On 12/4/06, Wendy Cheng <wcheng@...hat.com> wrote:
> Russell Cattelan wrote:
> > Wendy Cheng wrote:
> >
> >> Linux kernel, particularly the VFS layer, is starting to show signs
> >> of inadequacy as the software components built upon it keep growing.
> >> I have doubts that it can keep up and handle this complexity with a
> >> development policy like you just described (filesystem is a dumb
> >> layer ?). Aren't these DIO_xxx_LOCKING flags inside
> >> __blockdev_direct_IO() a perfect example why trying to do too many
> >> things inside vfs layer for so many filesystems is a bad idea ? By
> >> the way, since we're on this subject, could we discuss a little bit
> >> about vfs rename call (or I can start another new discussion thread) ?
> >>
> >> Note that linux do_rename() starts with the usual lookup logic,
> >> followed by "lock_rename", then a final round of dentry lookup, and
> >> finally comes to filesystem's i_op->rename call. Since lock_rename()
> >> only calls for vfs layer locks that are local to this particular
> >> machine, for a cluster filesystem, there exists a huge window between
> >> the final lookup and filesystem's i_op->rename calls such that the
> >> file could get deleted from another node before fs can do anything
> >> about it. Is it possible that we could get a new function pointer
> >> (lock_rename) in inode_operations structure so a cluster filesystem
> >> can do proper locking ?
> >
> > It looks like the ocfs2 guys have the similar problem?
> >
> > http://ftp.kernel.org/pub/linux/kernel/people/mfasheh/ocfs2/ocfs2_git_patches/ocfs2-upstream-linus-20060924/0009-PATCH-Allow-file-systems-to-manually-d_move-inside-of-rename.txt
> >
> >
> >
>
> Thanks for the pointer. Same as ocfs2, under current VFS code, both
> GFS1/2 also need FS_ODD_RENAME flag for the rename problem - got an ugly
> ~200 line draft patch ready for GFS1 (and am looking into GFS2 at this
> moment). The issue here is, for GFS, if vfs lock_rename() can call us,
> this complication can be greatly reduced. Will start another thread to
> see whether the wish can be granted.

Hi Wendy,

Have you (or others) made any progress on a possible solution to
simplify handling cluster fs do_rename() races (e.g. your proposed
lock_rename in inode_operations)?

I couldn't find a newer thread that continued this discussion...

please advise, thanks.
Mike
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