From: Goffredo Baroncelli <kreijack@inwind.it>
To: Shentino <shentino@gmail.com>
Cc: Michael <mike@draftx.net>, cwillu <cwillu@cwillu.com>,
linux-btrfs@vger.kernel.org
Subject: Re: rfc: fuzz testing by direct writes to device
Date: Wed, 05 Sep 2012 07:46:47 +0200 [thread overview]
Message-ID: <5046E747.7000209@inwind.it> (raw)
In-Reply-To: <CAGDaZ_pCsS=kC-yn5UvtZO7U1V9RzFUcch5=N6XnRxXu2cQoZQ@mail.gmail.com>
On 09/05/2012 03:59 AM, Shentino wrote:
>> > I am not sure that doing "sed</dev/sdX>/dev/sdX ..." is the right thing to
>> > do, because it rewrites the full disk. This means that:
>> > - it takes a lot of time
>> > - you don't have any control about which part of the disk you change: what
>> > happens if sed write a block which is update in parallel by BTRFS ?
> Which is one reason I used a sha1 hash of a random read as the search key :P
This doesn't change. The race would be the following:
1- kernel read a sector from the disk
2- sed read a sector from the disk
3- sed write a sector to the disk (the same data or an update one
doesn't matter)
4- kernel write an update sector to the disk
If 3 and 4 are different data the results are unpredictable. Yes it is a
very unlikely case, but it could happens.
prev parent reply other threads:[~2012-09-05 5:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-01 6:44 rfc: fuzz testing by direct writes to device Shentino
2012-09-01 8:10 ` Shentino
2012-09-01 15:41 ` Michael
2012-09-01 17:23 ` Shentino
2012-09-01 20:59 ` cwillu
2012-09-01 22:31 ` Shentino
2012-09-01 23:49 ` Michael
2012-09-02 1:03 ` Shentino
2012-09-02 5:44 ` David Sterba
2012-09-02 11:43 ` Shentino
2012-09-05 15:04 ` David Sterba
2012-09-05 21:23 ` Shentino
2012-09-04 18:15 ` Goffredo Baroncelli
2012-09-05 1:59 ` Shentino
2012-09-05 5:46 ` Goffredo Baroncelli [this message]
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