From: Christoph Hellwig <hch@infradead.org>
To: Miao Xie <miaox@cn.fujitsu.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Chris Mason <chris.mason@oracle.com>,
viro <viro@zeniv.linux.org.uk>,
Linux Btrfs <linux-btrfs@vger.kernel.org>,
Linux Fsdevel <linux-fsdevel@vger.kernel.org>,
Ito <t-itoh@jp.fujitsu.com>
Subject: Re: [PATCH 2/2] Btrfs: fix deadlock on sb->s_umount when doing umount
Date: Tue, 6 Dec 2011 06:23:23 -0500 [thread overview]
Message-ID: <20111206112322.GA10836@infradead.org> (raw)
In-Reply-To: <4EDDF740.6060100@cn.fujitsu.com>
On Tue, Dec 06, 2011 at 07:06:40PM +0800, Miao Xie wrote:
> > I can't see why you need the writeout when the trylocks fails. Umount
> > needs to take care of writing out all pending file data anyway, so doing
> > it from the cleaner thread in addition doesn't sound like it would help.
>
> umount invokes sync_fs() and write out all the dirty file data. For the
> other file systems, its OK because the file system does not introduce dirty pages
> by itself. But btrfs is different. Its automatic defragment will make lots of dirty
> pages after sync_fs() and reserve lots of meta-data space for those pages.
> And then the cleaner thread may find there is no enough space to reserve, it must
> sync the dirty file data and release the reserved space which is for the dirty
> file data.
I think the safest way to fix is is to write out all dirty data again
once the cleaner thread has been safely stopped.
next prev parent reply other threads:[~2011-12-06 11:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-06 5:35 [PATCH 2/2] Btrfs: fix deadlock on sb->s_umount when doing umount Miao Xie
2011-12-06 5:49 ` Al Viro
2011-12-06 6:52 ` Miao Xie
2011-12-06 9:59 ` Christoph Hellwig
2011-12-06 11:06 ` Miao Xie
2011-12-06 11:23 ` Christoph Hellwig [this message]
2011-12-06 21:36 ` Chris Mason
2011-12-07 2:31 ` Miao Xie
2011-12-07 11:11 ` Ilya Dryomov
2011-12-08 3:46 ` Miao Xie
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