linux-kernel - Re: Partition check considered as error is breaking mounting in 2.6.27

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Message-ID: <gagno4$pp9$1@ger.gmane.org>
Date:	Sat, 13 Sep 2008 11:54:44 -0400
From:	Bill Davidsen <davidsen@....com>
To:	linux-kernel@...r.kernel.org
Subject:  Re: Partition check considered as error is breaking mounting in 
  2.6.27

Andrew Morton wrote:
> On Fri, 12 Sep 2008 13:56:49 -0300
> Herton Ronaldo Krzesinski <herton@...driva.com.br> wrote:
> 
>> Recently I found a problem with a buggy camera that doesn't mount anymore with 
>> 2.6.27 (its memory is available via usb-storage), since commit 
>> 04ebd4aee52b06a2c38127d9208546e5b96f3a19
>>
>> The camera is an Olympus X-840. The original issue comes from the camera 
>> itself: its format program creates a partition with an off by one error, 
>> while the device reports that its memory has 42079 sectors, the partition 
>> table reports also that the only partition on the disk has the size of 42079, 
>> but it fails to account for the first sector in the memory that contains the 
>> partition table, so in the end the partition exceeds the limit of the device 
>> size (42080, first sector plus 42079 from the first partition).
>>
>> In previous kernels (2.6.26 and before), I still could mount and access the 
>> device (/dev/sdb1), although with the following errors:
> 
> Yeah.
> 
> Can you test this please?
> 
> From: Andrew Morton <akpm@...ux-foundation.org>
> 
> Herton Krzesinski reports that the error-checking changes in
> 04ebd4aee52b06a2c38127d9208546e5b96f3a19 ("block/ioctl.c and
> fs/partition/check.c: check value returned by add_partition") cause his
> buggy USB camera to no longer mount.  "The camera is an Olympus X-840. 
> The original issue comes from the camera itself: its format program
> creates a partition with an off by one error".
> 
> Buggy devices happen.  It is better for the kernel to warn and to proceed
> with the mount.
> 
> Reported-by: Herton Ronaldo Krzesinski <herton@...driva.com.br>
> Cc: Abdel Benamrouche <draconux@...il.com>
> Cc: Jens Axboe <jens.axboe@...cle.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  fs/partitions/check.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff -puN fs/partitions/check.c~rescan_partitions-make-device-capacity-errors-non-fatal fs/partitions/check.c
> --- a/fs/partitions/check.c~rescan_partitions-make-device-capacity-errors-non-fatal
> +++ a/fs/partitions/check.c
> @@ -540,7 +540,6 @@ int rescan_partitions(struct gendisk *di
>  		if (from + size > get_capacity(disk)) {
>  			printk(KERN_ERR " %s: p%d exceeds device capacity\n",
>  				disk->disk_name, p);
> -			continue;
>  		}
>  		res = add_partition(disk, p, from, size, state->parts[p].flags);
>  		if (res) {
> _
> 
I really like the patch Herton posted, with the big comment on why you don't 
want continue, to avoid repeating this conversation in a few years.

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

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