Re: [PATCH] drivers/scsi/sd.c: fix uninitialized variable in handling medium errors
- From: Andrew Morton <akpm@xxxxxxxx>
- Date: Wed, 26 Apr 2006 16:14:44 -0700
James Bottomley <James.Bottomley@xxxxxxxxxxxx> wrote:
On Wed, 2006-04-26 at 16:27 -0400, Mark Lord wrote:
From: Mark Lord <lkml@xxxxxx>
I am looking into how SCSI/SATA handle medium (disk) errors,
and the observed behaviour is a little more random than expected,
due to a bug in sd.c.
When scsi_get_sense_info_fld() fails (returns 0), it does NOT update the
value of first_err_block. But sd_rw_intr() merrily continues to use that
variable regardless, possibly making incorrect decisions about retries and the like.
This patch removes the randomness there, by using the first sector of the
request (SCpnt->request->sector) in such cases, instead of first_err_block.
The patch shows more context than usual, to help see what's going on.
Thanks for finding the bug. Your solution is a bit, um, convoluted.
What it should really be doing if we find no valid information field is
a break so we go out with the default good_sectors of zero (rather than
arriving at that value via a circuitous route).
And, of course, I couldn't resist eliminating the superfluous info_valid
variable and tidying the logic to be programmatic instead of a switch
case. How does this work?
It'd be nice to have something simple-and-obvious for the
simple-and-obvious -stable maintainers. That's if we think -stable needs
this fixed.
+ int sector_size_div =
+ 512 / SCpnt->device->sector_size;
+ error_sector /= sector_size_div;
You sure about this bit?
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