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Re: [Qemu-devel] [PATCH v7 06/19] scsi-disk: Switch to byte-based aio bl


From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH v7 06/19] scsi-disk: Switch to byte-based aio block access
Date: Tue, 10 May 2016 16:49:55 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Am 10.05.2016 um 14:56 hat Eric Blake geschrieben:
> On 05/10/2016 02:55 AM, Kevin Wolf wrote:
> > Am 06.05.2016 um 18:26 hat Eric Blake geschrieben:
> >> Sector-based blk_aio_readv() and blk_aio_writev() should die; switch
> >> to byte-based blk_aio_preadv() and blk_aio_pwritev() instead.
> >>
> >> As part of the cleanup, scsi_init_iovec() no longer needs to return
> >> a value, and reword a comment.
> >>
> >> Signed-off-by: Eric Blake <address@hidden>
> >>
> 
> >> @@ -118,7 +118,6 @@ static uint32_t scsi_init_iovec(SCSIDiskReq *r, size_t 
> >> size)
> >>      }
> >>      r->iov.iov_len = MIN(r->sector_count * 512, r->buflen);
> >>      qemu_iovec_init_external(&r->qiov, &r->iov, 1);
> >> -    return r->qiov.size / 512;
> > 
> > The return value was MIN(r->sector_count, SCSI_DMA_BUF_SIZE / 512).
> > 
> >>  }
> >>
> >>  static void scsi_disk_save_request(QEMUFile *f, SCSIRequest *req)
> 
> >> -        n = scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
> >> +        scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
> >>          block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
> >> -                         n * BDRV_SECTOR_SIZE, BLOCK_ACCT_READ);
> >> -        r->req.aiocb = blk_aio_readv(s->qdev.conf.blk, r->sector, 
> >> &r->qiov, n,
> >> -                                     scsi_read_complete, r);
> >> +                         SCSI_DMA_BUF_SIZE, BLOCK_ACCT_READ);
> > 
> > But here you use SCSI_DMA_BUF_SIZE without considering r->sector_count.
> > Is this correct or are requests that are smaller than SCSI_DMA_BUF_SIZE
> > now accounted for more data than they actually read?
> > 
> > Would r->qiov.size be more obviously correct? You did that for writes.
> 
> Yes. Is that something you are able to fix on commit, or should I submit
> a fixup?

Okay, I can fix it up while applying.

Kevin

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