linux-ext4 - Re: [PATCH 00/27 v6] Fix filesystem freezing deadlocks

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Date:	Sat, 9 Jun 2012 07:29:52 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-fsdevel@...r.kernel.org, dchinner@...hat.com,
	Alex Elder <elder@...nel.org>,
	Anton Altaparmakov <anton@...era.com>, Ben Myers <bpm@....com>,
	Chris Mason <chris.mason@...cle.com>, cluster-devel@...hat.com,
	"David S. Miller" <davem@...emloft.net>,
	fuse-devel@...ts.sourceforge.net,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Joel Becker <jlbec@...lplan.org>,
	KONISHI Ryusuke <konishi.ryusuke@....ntt.co.jp>,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-nilfs@...r.kernel.org,
	linux-ntfs-dev@...ts.sourceforge.net,
	Mark Fasheh <mfasheh@...e.com>,
	Miklos Szeredi <miklos@...redi.hu>, ocfs2-devel@....oracle.com,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Theodore Ts'o <tytso@....edu>, xfs@....sgi.com
Subject: Re: [PATCH 00/27 v6] Fix filesystem freezing deadlocks

On Sat, Jun 02, 2012 at 12:30:14AM +0200, Jan Kara wrote:
>   Hello,
> 
>   here is the sixth iteration of my patches to improve filesystem freezing.
> The change since last iteration is that filesystem can be frozen with open but
> unlinked files. After some thinking, I've decided that the best way to handle
> this is to block removal inside ->evict_inode() of each filesystem and use
> fs-internal level of freeze protection for that (usually I've instrumented
> filesystem's transaction system to use freeze protection). Handling
> inside VFS would be less work but the only level of freeze protection that
> has a chance of not causing deadlocks is the one used for page faults and even
> there it's not clear lock ordering would be correct wrt some fs-specific locks.
> I've converted ext2, ext4, btrfs, xfs, nilfs2, ocfs2, gfs2 and also checked
> that ext3, reiserfs, jfs should work as well (they have their internal freeze
> protection mechanisms, possibly they could be replaced by a generic one but
> given these are mostly aging filesystems, it's not a real priority IHMO).
> So finally I'm not aware of any pending issue with this patch set so if you
> have some concern, please speak up!

Could you rebase on top of e.g. -rc2 and repost?
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