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

To: Surbhi Palande <surbhi.palande@xxxxxxxxxxxxx>
Subject: Re: [PATCH] Attempt to sync the fsstress writes to a frozen F.S
From: Eric Sandeen <sandeen@xxxxxxxxxx>
Date: Thu, 12 May 2011 09:22:54 -0500
Cc: jack@xxxxxxx, marco.stornelli@xxxxxxxxx, adilger.kernel@xxxxxxxxx, toshi.okajima@xxxxxxxxxxxxxx, tytso@xxxxxxx, m.mizuma@xxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs-oss <xfs@xxxxxxxxxxx>
In-reply-to: <1305097841-2308-1-git-send-email-surbhi.palande@xxxxxxxxxxxxx>
References: <4DCA3583.7010904@xxxxxxxxxxxxx> <1305097841-2308-1-git-send-email-surbhi.palande@xxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10
On 5/11/11 2:10 AM, 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@xxxxxxxxxxxxx>

Seems ok to me.  In the future, when sending xfstests patches,
if you can add "xfstests" to the subject, and cc: the xfs list,
it'd be great.

I presume that this test does fail for you without your fixes?

I'll see if anyone on the xfs list has comments and if not, I can check this in.

Thanks,
-Eric

> ---
>  068 |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/068 b/068
> index 82c1a4e..b9ac58d 100755
> --- a/068
> +++ b/068
> @@ -101,6 +101,11 @@ do
>           tee -a $seq.full
>       sleep 2
>  
> +     # there should be nothing to sync at this point. This may hang in case
> +     # of fsstress background writes dirtying the page cache while the F.S 
> is frozen
> +     sync &
> +     sleep 2
> +
>       echo "*** thawing  \$SCRATCH_MNT" | tee -a $seq.full
>       xfs_freeze -u "$SCRATCH_MNT" | tee -a $seq.full
>       [ $? != 0 ] && echo xfs_freeze -u "$SCRATCH_MNT" failed | \

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