linux-kernel - Re: [PATCH 00/11 v2] Push file_update_time() into .page

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Message-ID: <20120301122319.GE4385@quack.suse.cz>
Date:	Thu, 1 Mar 2012 13:23:19 +0100
From:	Jan Kara <jack@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, dchinner@...hat.com,
	Jan Kara <jack@...e.cz>, Jaya Kumar <jayalk@...works.biz>,
	Sage Weil <sage@...dream.net>, ceph-devel@...r.kernel.org,
	Steve French <sfrench@...ba.org>, linux-cifs@...r.kernel.org,
	Eric Van Hensbergen <ericvh@...il.com>,
	Ron Minnich <rminnich@...dia.gov>,
	Latchesar Ionkov <lucho@...kov.net>,
	v9fs-developer@...ts.sourceforge.net,
	Miklos Szeredi <miklos@...redi.hu>,
	fuse-devel@...ts.sourceforge.net,
	Steven Whitehouse <swhiteho@...hat.com>,
	cluster-devel@...hat.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 00/11 v2] Push file_update_time() into .page_mkwrite

  Bah, the subject should have been 0/9... Sorry.

								Honza
On Thu 01-03-12 12:41:34, Jan Kara wrote:
>   Hello,
> 
>   to provide reliable support for filesystem freezing, filesystems need to have
> complete control over when metadata is changed. In particular,
> file_update_time() calls from page fault code make it impossible for
> filesystems to prevent inodes from being dirtied while the filesystem is
> frozen.
> 
> To fix the issue, this patch set changes page fault code to call
> file_update_time() only when ->page_mkwrite() callback is not provided. If the
> callback is provided, it is the responsibility of the filesystem to perform
> update of i_mtime / i_ctime if needed. We also push file_update_time() call
> to all existing ->page_mkwrite() implementations if the time update does not
> obviously happen by other means. If you know your filesystem does not need
> update of modification times in ->page_mkwrite() handler, please speak up and
> I'll drop the patch for your filesystem.
> 
> As a side note, an alternative would be to remove call of file_update_time()
> from page fault code altogether and require all filesystems needing it to do
> that in their ->page_mkwrite() implementation. That is certainly possible
> although maybe slightly inefficient and would require auditting 100+
> vm_operations_structs *shiver*.
> 
> Changes since v1:
> * Dropped patches for filesystems which don't need them
> * Added some acks
> * Improved sysfs patch by Alex Elder's suggestion
> 
> Andrew, would you be willing to merge these patches via your tree?
> 
> 								Honza
> 
> CC: Jaya Kumar <jayalk@...works.biz>
> CC: Sage Weil <sage@...dream.net>
> CC: ceph-devel@...r.kernel.org
> CC: Steve French <sfrench@...ba.org>
> CC: linux-cifs@...r.kernel.org
> CC: Eric Van Hensbergen <ericvh@...il.com>
> CC: Ron Minnich <rminnich@...dia.gov>
> CC: Latchesar Ionkov <lucho@...kov.net>
> CC: v9fs-developer@...ts.sourceforge.net
> CC: Miklos Szeredi <miklos@...redi.hu>
> CC: fuse-devel@...ts.sourceforge.net
> CC: Steven Whitehouse <swhiteho@...hat.com>
> CC: cluster-devel@...hat.com
> CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
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-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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