linux-ext4 - Re: [PATCH] Attempt to sync the fsstress writes to a frozen F.S

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Message-ID: <20110524214222.GF26055@thunk.org>
Date:	Tue, 24 May 2011 17:42:23 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Surbhi Palande <surbhi.palande@...onical.com>
Cc:	sandeen@...hat.com, jack@...e.cz, marco.stornelli@...il.com,
	adilger.kernel@...ger.ca, toshi.okajima@...fujitsu.com,
	m.mizuma@...fujitsu.com, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] Attempt to sync the fsstress writes to a frozen F.S

On Wed, May 11, 2011 at 10:10:41AM +0300, Surbhi Palande wrote:
> While the fsstress background writes are busy dirtying the page cache, if a
> fsfreeze happens then the background writes should stall. A sync should then
> not have any data to sync to the FS. If it does have any data to sync then
> sync will cause a deadlock by holding the s_umount write semaphore and waiting
> in the wait queue for the FS to thaw, whereas the F.S can never thaw without
> getting the s_umount write semaphore.
> 
> Signed-off-by: Surbhi Palande <surbhi.palande@...onical.com>

Hi Surbhi,

Have you tried out Jan Kara's patches?

[1/3] fs: Create __block_page_mkwrite() helper passing error values back
[2/3] vfs: Block mmapped writes while the fs is frozen
[3/3] ext4: Rewrite ext4_page_mkwrite() to return locked page

Do these patches fix the problem you've been trying to fix with your
patches?  I believe they should, but I would appreciate confirmation
that with these patches, you're no longer able to reproduce the
problem you've been concerned about.

Thanks, regards,

						- Ted
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