From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Matthew Wilcox <matthew@wil.cx>
Cc: FUJITA Tomonori <tomof@acm.org>,
dougg@torque.net, linux-scsi@vger.kernel.org,
fujita.tomonori@lab.ntt.co.jp
Subject: Re: [PATCH] scsi_debug: disable clustering
Date: Sun, 17 Feb 2008 08:18:11 -0600 [thread overview]
Message-ID: <1203257892.3082.11.camel@localhost.localdomain> (raw)
In-Reply-To: <20080217141045.GB21012@parisc-linux.org>
On Sun, 2008-02-17 at 07:10 -0700, Matthew Wilcox wrote:
> On Sat, Feb 16, 2008 at 11:57:15PM +0900, FUJITA Tomonori wrote:
> > scsi_debug does at several places:
> >
> > for_each_sg(sdb->table.sgl, sg, sdb->table.nents, k) {
> > kaddr = (unsigned char *)
> > kmap_atomic(sg_page(sg), KM_USER0);
> >
> >
> > We cannot do something like that with the clustering enabled (or we
> > can use scsi_kmap_atomic_sg).
>
> Why not? Is KM_USER0 used for something else with clstering enabled?
No, he means that kmap_atomic can only map a page of data. This makes
single page only sg list entries and input assumption into this loop.
with ENABLE_CLUSTERING, that's potentially not true. Of course, this
accidentally works most of the time because of the way kmap functions.
James
next prev parent reply other threads:[~2008-02-17 14:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-16 14:57 [PATCH] scsi_debug: disable clustering FUJITA Tomonori
2008-02-17 5:53 ` Douglas Gilbert
2008-02-17 14:10 ` Matthew Wilcox
2008-02-17 14:18 ` James Bottomley [this message]
2008-02-17 14:28 ` Matthew Wilcox
2008-02-17 14:52 ` FUJITA Tomonori
2008-02-17 15:02 ` James Bottomley
2008-02-17 15:11 ` FUJITA Tomonori
2008-02-17 15:22 ` James Bottomley
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