Re: [PATCH 0/6] add large command support to the block layer

[Jens Axboe <jens.axboe@oracle.com>]

On Tue, Apr 29 2008, FUJITA Tomonori wrote:
> On Tue, 29 Apr 2008 14:37:12 +0200
> Jens Axboe <jens.axboe@oracle.com> wrote:
> 
> > On Tue, Apr 29 2008, FUJITA Tomonori wrote:
> > > On Tue, 29 Apr 2008 13:55:13 +0200
> > > "Bartlomiej Zolnierkiewicz" <bzolnier@gmail.com> wrote:
> > > 
> > > > On Tue, Apr 29, 2008 at 9:54 AM, Jens Axboe <jens.axboe@oracle.com> wrote:
> > > > >
> > > > > On Sat, Apr 26 2008, FUJITA Tomonori wrote:
> > > > >  > This is an updated patchset for large command support to the block
> > > > >  > layer:
> > > > >  >
> > > > >  > http://marc.info/?l=linux-scsi&m=120817127118449&w=2
> > > > >  >
> > > > >  > We rarely handle large commands. So for optimization, a struct request
> > > > >  > still has a static array for a command. rq_init sets rq->cmd pointer
> > > > >  > to the static array. In short, rq_init() does
> > > > >  >
> > > > >  > rq->cmd = rq->__cmd;
> > > > >  >
> > > > >  > So we can access to rq->cmd and rq->cmd_len as before.
> > > > >  >
> > > > >  > This change requires everyone to initialize the request in a proper
> > > > >  > way (that is, just doing a memset() will not work). Now we have
> > > > >  > rq_init() that works for any path so this patchset can cleanly convert
> > > > >  > users of requests on the stack or kmalloced requests to use it (the
> > > > >  > previous patchset does it in a hacky way):
> > > > >  >
> > > > >  > http://marc.info/?l=linux-scsi&m=120911792725876&w=2
> > > > >  >
> > > > >  > This patchset is against Jens' for-linus branch.
> > > > >  >
> > > > >  > #1-#4 patches can be applied via Jens' tree now. #5 patch is for
> > > > >  > IDE. It cleanly can be applied to both Bart's latest quilt tree and
> > > > >  > Jens' tree though Bart's quilt tree has some pending IDE patches. #4
> > > > >  > patch depends on #4. #6 patch depends on #1-#5.
> > > > >  >
> > > > >  > I guess that the easiest way to apply this patchset would be:
> > > > >  >
> > > > >  > 1. Pushing Bart's quilt tree to mainline.
> > > > >  > 2. Rebasing Jens' tree to mainline.
> > > > >  > 3. Pushing this patchset via Jens' tree.
> > > > >  >
> > > > >  > Jens and Bart, let me know if I can do something to make the process
> > > > >  > easier.
> > > > >  >
> > > > >  > Bart, I will try to push the patchset to remove the requests on the
> > > > >  > stack for 2.6.27:
> > > > >  >
> > > > >  > http://marc.info/?l=linux-ide&m=120882410712466&w=2
> > > > >
> > > > >  I've applied all patches to the for-linus branch, it should go up
> > > > >  soonish. If anyone has problems with this, please holler SOON.
> > > > 
> > > > Fine with me (patches look good and survived quick testing).
> > > 
> > > Thanks,
> > > 
> > > 
> > > > My only concern is that the final series from Tomo lacked
> > > > 
> > > > 	"block: replace sizeof(rq->cmd) with BLK_MAX_CDB"
> > > > 
> > > > and it is also not in for-linus branch (it has to be merged
> > > > before "block: add large command support" patch or ide-cd
> > > > will break).
> > > 
> > > Sorry, somehow I forgot to put it in the patchset. Yeah, probabaly
> > > initializing only 4 (or 8) bytes in rq->cmd would not work for ide-cd.
> > > 
> > > Jens, please put this to the for-linus branch.
> > 
> > Done, please inspect the result (and ordering), thanks.
> 
> Thanks, it should work.
> 
> BTW, I think that the commit 09225d2 in for-linus branch (block: make
> queue flags non-atomic) needs to export blk_run_queue.

Good spotting, it does. Fixed up.

-- 
Jens Axboe