From: Jens Axboe <axboe@kernel.dk>
To: Hannes Reinecke <hare@suse.de>,
"Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Mike Snitzer <snitzer@redhat.com>, Brian King <brking@us.ibm.com>,
linux-scsi@vger.kernel.org, linux-block@vger.kernel.org,
mark.bergman@uphs.upenn.edu
Subject: Re: block: don't check request size in blk_cloned_rq_check_limits()
Date: Wed, 15 Jun 2016 12:03:40 +0200 [thread overview]
Message-ID: <576127FC.9020608@kernel.dk> (raw)
In-Reply-To: <5760F6BC.60109@suse.de>
On 06/15/2016 08:33 AM, Hannes Reinecke wrote:
> And as I've mentioned before: what is the purpose of this check?
>
> 'max_sectors' and 'max_hw_sectors' are checked during request assembly,
> and those limits are not changed even after calling
> blk_recalc_rq_segments(). And if we go over any device-imposed
> restrictions we'll be getting an I/O error from the driver anyway.
> So why have it at all?
You don't know that to be the case. The driver asked for certain limits,
the core MUST obey them. The driver should not need to check for these
limits, outside of in a BUG_ON() like manner.
> Especially as the system boots happily with this check removed...
That's the case for you, but you can't assume this to be the case in
general.
There's a _lot_ of hand waving in this thread, Hannes. How do we
reproduce this? We need to get this fixed for real, not just delete some
check that triggers for you and that it just happens to work without.
That's not how you fix problems.
--
Jens Axboe
next prev parent reply other threads:[~2016-06-15 10:03 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 7:24 [PATCH] block: don't check request size in blk_cloned_rq_check_limits() Hannes Reinecke
2016-06-10 13:19 ` Mike Snitzer
2016-06-10 13:30 ` Hannes Reinecke
2016-06-10 14:18 ` Mike Snitzer
2016-06-11 10:05 ` Hannes Reinecke
2016-06-11 2:22 ` Martin K. Petersen
2016-06-11 10:01 ` Hannes Reinecke
2016-06-11 11:06 ` Martin K. Petersen
2016-06-11 13:10 ` Hannes Reinecke
2016-06-13 8:07 ` Christoph Hellwig
2016-06-15 1:39 ` Martin K. Petersen
2016-06-15 2:29 ` Mike Snitzer
2016-06-15 2:32 ` Martin K. Petersen
2016-06-15 6:33 ` Hannes Reinecke
2016-06-15 10:03 ` Jens Axboe [this message]
2016-06-15 10:33 ` Hannes Reinecke
2016-06-15 16:34 ` Brian King
2016-06-16 12:35 ` Mauricio Faria de Oliveira
2016-06-16 21:59 ` Mauricio Faria de Oliveira
2016-06-17 6:59 ` Hannes Reinecke
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