From: Jan Kara <jack@suse.cz>
To: Boaz Harrosh <openosd@gmail.com>
Cc: Jan Kara <jack@suse.cz>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
linux-xfs@vger.kernel.org, linux-mm@kvack.org,
Amir Goldstein <amir73il@gmail.com>,
Boaz Harrosh <boaz@plexistor.com>,
linux-fsdevel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 3/3] xfs: Fix stale data exposure when readahead races with hole punch
Date: Tue, 24 Sep 2019 17:23:37 +0200 [thread overview]
Message-ID: <20190924152337.GE11819@quack2.suse.cz> (raw)
In-Reply-To: <53b7b7b9-7ada-650c-0a32-291a242601f3@gmail.com>
On Mon 23-09-19 15:33:05, Boaz Harrosh wrote:
> On 18/09/2019 15:31, Jan Kara wrote:
> <>
> >>> Is there a test on xfstests to demonstrate this race?
> >>
> >> No, but I can try to create one.
> >
> > I was experimenting with this but I could not reproduce the issue in my
> > test VM without inserting artificial delay at appropriate place... So I
> > don't think there's much point in the fstest for this.
> >
> > Honza
> >
>
> If I understand correctly you will need threads that direct-write
> files, then fadvise(WILL_NEED) - in parallel to truncate (punch_hole) these
> files - In parallel to trash caches.
> (Direct-write is so data is not present in cache when you come to WILL_NEED
> it into the cache, otherwise the xfs b-trees are not exercised. Or are you
> more worried about the page_cache races?
> )
What I was testing was:
Fill file with data.
One process does fadvise(WILLNEED) block by block from end of the file.
Another process punches hole into the file.
If they race is the right way, following read will show old data instead of
zeros. And as I said I'm able to hit this but only if I add artificial
delay between truncating page cache and actually removing blocks.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-09-24 15:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190829131034.10563-1-jack@suse.cz>
2019-08-29 13:10 ` [PATCH 1/3] mm: Handle MADV_WILLNEED through vfs_fadvise() Jan Kara
2019-08-29 15:49 ` Darrick J. Wong
2019-08-29 13:10 ` [PATCH 2/3] fs: Export generic_fadvise() Jan Kara
2019-08-29 13:10 ` [PATCH 3/3] xfs: Fix stale data exposure when readahead races with hole punch Jan Kara
2019-08-29 15:52 ` Darrick J. Wong
2019-08-30 15:24 ` Jan Kara
2019-08-30 16:02 ` Darrick J. Wong
2019-09-18 12:31 ` Jan Kara
2019-09-18 16:07 ` Darrick J. Wong
2019-09-23 12:33 ` Boaz Harrosh
2019-09-24 15:23 ` Jan Kara [this message]
2019-09-24 15:45 ` Boaz Harrosh
[not found] <20190711140012.1671-1-jack@suse.cz>
2019-07-11 14:00 ` Jan Kara
2019-07-11 15:28 ` Amir Goldstein
2019-07-11 15:49 ` Darrick J. Wong
2019-07-12 12:00 ` Jan Kara
2019-07-12 17:56 ` Darrick J. Wong
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