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Message-ID: <20120416161620.GC6852@quack.suse.cz> Date: Mon, 16 Apr 2012 18:16:20 +0200 From: Jan Kara <jack@...e.cz> To: Al Viro <viro@...IV.linux.org.uk> Cc: dchinner@...hat.com, LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org, Jan Kara <jack@...e.cz>, 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 00/19 v5] Fix filesystem freezing deadlocks The subject should have been [PATCH 00/27]... Sorry for the mistake. Honza On Mon 16-04-12 18:13:38, Jan Kara wrote: > Hello, > > here is the fifth iteration of my patches to improve filesystem freezing. > No serious changes since last time. Mostly I rebased patches and merged this > series with series moving file_update_time() to ->page_mkwrite() to simplify > testing and merging. > > Filesystem freezing is currently racy and thus we can end up with dirty data on > frozen filesystem (see changelog patch 13 for detailed race description). This > patch series aims at fixing this. > > To be able to block all places where inodes get dirtied, I've moved filesystem > file_update_time() call to ->page_mkwrite callback (patches 01-07) and put > freeze handling in mnt_want_write() / mnt_drop_write(). That however required > some code shuffling and changes to kern_path_create() (see patches 09-12). I > think the result is OK but opinions may differ ;). The advantage of this change > also is that all filesystems get freeze protection almost for free - even ext2 > can handle freezing well now. > > Another potential contention point might be patch 19. In that patch we make > freeze_super() refuse to freeze the filesystem when there are open but unlinked > files which may be impractical in some cases. The main reason for this is the > problem with handling of file deletion from fput() called with mmap_sem held > (e.g. from munmap(2)), and then there's the fact that we cannot really force > such filesystem into a consistent state... But if people think that freezing > with open but unlinked files should happen, then I have some possible > solutions in mind (maybe as a separate patchset since this is large enough). > > I'm not able to hit any deadlocks, lockdep warnings, or dirty data on frozen > filesystem despite beating it with fsstress and bash-shared-mapping while > freezing and unfreezing for several hours (using ext4 and xfs) so I'm > reasonably confident this could finally be the right solution. > > Changes since v4: > * added a couple of Acked-by's > * added some comments & doc update > * added patches from series "Push file_update_time() into .page_mkwrite" > since it doesn't make much sense to keep them separate anymore > * rebased on top of 3.4-rc2 > > Changes since v3: > * added third level of freezing for fs internal purposes - hooked some > filesystems to use it (XFS, nilfs2) > * removed racy i_size check from filemap_mkwrite() > > Changes since v2: > * completely rewritten > * freezing is now blocked at VFS entry points > * two stage freezing to handle both mmapped writes and other IO > > The biggest changes since v1: > * have two counters to provide safe state transitions for SB_FREEZE_WRITE > and SB_FREEZE_TRANS states > * use percpu counters instead of own percpu structure > * added documentation fixes from the old fs freezing series > * converted XFS to use SB_FREEZE_TRANS counter instead of its private > m_active_trans counter > > Honza > > CC: Alex Elder <elder@...nel.org> > CC: Anton Altaparmakov <anton@...era.com> > CC: Ben Myers <bpm@....com> > CC: Chris Mason <chris.mason@...cle.com> > CC: cluster-devel@...hat.com > CC: "David S. Miller" <davem@...emloft.net> > CC: fuse-devel@...ts.sourceforge.net > CC: "J. Bruce Fields" <bfields@...ldses.org> > CC: Joel Becker <jlbec@...lplan.org> > CC: KONISHI Ryusuke <konishi.ryusuke@....ntt.co.jp> > CC: linux-btrfs@...r.kernel.org > CC: linux-ext4@...r.kernel.org > CC: linux-nfs@...r.kernel.org > CC: linux-nilfs@...r.kernel.org > CC: linux-ntfs-dev@...ts.sourceforge.net > CC: Mark Fasheh <mfasheh@...e.com> > CC: Miklos Szeredi <miklos@...redi.hu> > CC: ocfs2-devel@....oracle.com > CC: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> > CC: Steven Whitehouse <swhiteho@...hat.com> > CC: "Theodore Ts'o" <tytso@....edu> > CC: xfs@....sgi.com -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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