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

[Bill Davidsen]

Andrew Morton wrote:
> On Fri, 12 Sep 2008 13:56:49 -0300
> Herton Ronaldo Krzesinski <herton@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Cc: Abdel Benamrouche <draconux@xxxxxxxxx>
> Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>
>  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@xxxxxxx>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

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