From: Jan Kara Subject: Re: [PATCH 00/19 v5] Fix filesystem freezing deadlocks Date: Mon, 16 Apr 2012 18:16:20 +0200 Message-ID: <20120416161620.GC6852@quack.suse.cz> References: <1334592845-22862-1-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dchinner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, LKML , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jan Kara , Alex Elder , Anton Altaparmakov , Ben Myers , Chris Mason , cluster-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, "David S. Miller" , fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, "J. Bruce Fields" , Joel Becker , KONISHI Ryusuke , linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ntfs-dev-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Mark Fasheh , Miklos Szeredi , ocfs2-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org, OGAWA Hirofumi , Steven Whitehouse , Theodore Ts'o , xfs-VZNHf3L845pBDgjK7y7TUQ@public.gmane.org To: Al Viro Return-path: Content-Disposition: inline In-Reply-To: <1334592845-22862-1-git-send-email-jack-AlSwsSmVLrQ@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org 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 > CC: Anton Altaparmakov > CC: Ben Myers > CC: Chris Mason > CC: cluster-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org > CC: "David S. Miller" > CC: fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org > CC: "J. Bruce Fields" > CC: Joel Becker > CC: KONISHI Ryusuke > CC: linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: linux-ntfs-dev-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org > CC: Mark Fasheh > CC: Miklos Szeredi > CC: ocfs2-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org > CC: OGAWA Hirofumi > CC: Steven Whitehouse > CC: "Theodore Ts'o" > CC: xfs-VZNHf3L845pBDgjK7y7TUQ@public.gmane.org -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html