linux-kernel - Re: Kernel crashing on eject SD card

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Message-ID: <20120214143119.345fead9@stein>
Date:	Tue, 14 Feb 2012 14:31:19 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	"Jun'ichi Nomura" <j-nomura@...jp.nec.com>
Cc:	Naveen Goswamy <naveen.goswamy@...ymtl.ca>,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Dave Jones <davej@...hat.com>, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: Re: Kernel crashing on eject SD card

On Feb 14 Jun'ichi Nomura wrote:
> According to the comments by Huajun Li:
> http://www.spinics.net/lists/linux-scsi/msg55698.html
> 
> The following commit has changed __blkdev_get() to end up calling
> sd_revalidate_disk() without getting a refcount of scsi_device:
> 
>   commit 1196f8b814f32cd04df334abf47648c2a9fd8324
>   Author: Tejun Heo <tj@...nel.org>
>   Date:   Thu Apr 21 20:54:45 2011 +0200
> 
>     block: rescan partitions on invalidated devices on -ENOMEDIA too
> 
> that could lead to oops like this:
> 
>   process A                  process B
>   ----------------------------------------------
>   sys_open
>     __blkdev_get
>       sd_open
>         returns -ENOMEDIUM
>                              scsi_remove_device
>                                <scsi_device torn down>
>       rescan_partitions
>         sd_revalidate_disk
>           <oops>
> 
> Should "revalidate_disk" of block_device_operations work
> without successful open()?
> 
> If so, sd_revalidate_disk() (and possibly other drivers) needs to be
> fixed. (e.g. use scsi_disk_get/put by itself)
> 
> If not, __blkdev_get() or rescan_partision() should avoid calling
> "revalidate_disk" for -ENOMEDIUM case.

It may very well be that not only sd_revalidate_disk is affected.

I have yet to check whether the "open -> unplug -> ioctl -> oops" bug from
http://www.spinics.net/lists/linux-scsi/msg56254.html
(a) happens under 3.3-rc still (was reported against 3.2-rc7),
(b) affects sd devices too (was reported against sr devices).
-- 
Stefan Richter
-=====-===-- --=- -===-
http://arcgraph.de/sr/
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