From: Hannes Reinecke <hare@suse.de>
To: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: jejb@linux.ibm.com, martin.petersen@oracle.com,
linux-scsi@vger.kernel.org, stefanha@redhat.com
Subject: Re: [PATCH 1/2] scsi_host: add support for request batching
Date: Fri, 5 Jul 2019 09:12:37 +0200 [thread overview]
Message-ID: <c1d16dbf-713d-3528-78d7-a3f49c056f74@suse.de> (raw)
In-Reply-To: <afea12a1-47b3-0ebe-a3c2-6adc615bbddf@redhat.com>
On 7/4/19 3:19 PM, Paolo Bonzini wrote:
> On 19/06/19 12:31, Paolo Bonzini wrote:
>>> I'm a bit unsure if 'bd->last' is always set; it's quite obvious that
>>> it's present if set, but what about requests with 'bd->last == false' ?
>>> Is there a guarantee that they will _always_ be followed with a request
>>> with bd->last == true?
>>> And if so, is there a guarantee that this request is part of the same batch?
>> It's complicated. A request with bd->last == false _will_ always be
>> followed by a request with bd->last == true in the same batch. However,
>> due to e.g. errors it may be possible that the last request is not sent.
>> In that case, the block layer sends commit_rqs, as documented in the
>> comment above, to flush the requests that have been sent already.
>>
>> So, a driver that obeys bd->last (or SCMD_LAST) but does not implement
>> commit_rqs is bound to have bugs, which is why this patch was not split
>> further.
>>
>> Makes sense?
>
> Hannes, can you provide your Reviewed-by?
>
Well ... since you asked for it:
Where is the 'commit_rqs' callback actually used?
I seem to be going blind, but I can't find it; should be somewhere in
the first patch, no?
As per description:
* The commit_rqs function is used to trigger a hardware
* doorbell after some requests have been queued with
* queuecommand, when an error is encountered before sending
* the request with SCMD_LAST set.
So it should be somewhere in the error path, probably scsi_error or
something. But I don't seem to be able to find it ...
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)
next prev parent reply other threads:[~2019-07-05 7:12 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 11:28 [PATCH 0/2] scsi: add support for request batching Paolo Bonzini
2019-05-30 11:28 ` [PATCH 1/2] scsi_host: " Paolo Bonzini
2019-05-30 15:36 ` Bart Van Assche
2019-05-30 15:54 ` Paolo Bonzini
2019-05-30 17:54 ` Bart Van Assche
2019-05-31 9:12 ` Paolo Bonzini
2019-05-31 3:27 ` Ming Lei
2019-06-03 8:16 ` Paolo Bonzini
2019-07-05 1:00 ` Ming Lei
2019-06-04 22:40 ` Bart Van Assche
2019-06-19 8:11 ` Hannes Reinecke
2019-06-19 10:31 ` Paolo Bonzini
2019-07-04 13:19 ` Paolo Bonzini
2019-07-05 7:12 ` Hannes Reinecke [this message]
2019-07-05 7:44 ` Stefan Hajnoczi
2019-07-05 7:51 ` Hannes Reinecke
2019-05-30 11:28 ` [PATCH 2/2] virtio_scsi: implement " Paolo Bonzini
2019-05-30 17:28 ` Bart Van Assche
2019-05-31 9:03 ` Paolo Bonzini
2019-07-05 7:52 ` Hannes Reinecke
2019-07-08 9:47 ` Ming Lei
2019-06-10 12:36 ` [PATCH 0/2] scsi: add support for " Stefan Hajnoczi
2019-06-26 13:51 ` Paolo Bonzini
2019-06-26 14:14 ` Douglas Gilbert
2019-06-26 14:50 ` Paolo Bonzini
2019-06-27 3:37 ` Martin K. Petersen
2019-06-27 8:17 ` Paolo Bonzini
2019-07-05 7:13 ` Hannes Reinecke
2019-07-05 11:58 ` Paolo Bonzini
2019-07-12 1:37 ` Martin K. Petersen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=c1d16dbf-713d-3528-78d7-a3f49c056f74@suse.de \
--to=hare@suse.de \
--cc=jejb@linux.ibm.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=pbonzini@redhat.com \
--cc=stefanha@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).