From: James Bottomley <James.Bottomley@SteelEye.com>
To: Jens Axboe <axboe@suse.de>
Cc: SCSI Mailing List <linux-scsi@vger.kernel.org>, g.liakhovetski@gmx.de
Subject: Re: [PATCH] dc395x: Fix support for highmem
Date: Wed, 16 Mar 2005 09:13:36 -0600 [thread overview]
Message-ID: <1110986016.5771.3.camel@mulgrave> (raw)
In-Reply-To: <20050316075839.GC7842@suse.de>
On Wed, 2005-03-16 at 08:58 +0100, Jens Axboe wrote:
> Guys, who reviewed this? It looks completely bogus, using kmap() for tha
> entire sg list is just wrong and can deadlock easily. The proper way is
> of course to skip the virtual address requirement and dma map the sg
> array properly.
I suppose ultimately, the responsibility is mine.
The problem with this particular card (at least as I read the comments
in the driver) is that most of the time, it can actually do DMA on its
own. However, when something unexpected occurs (Like a SCSI device
disconnections), the DMA engine halts and the last pieces of data have
to be read in manually using PIO.
I agree the kmap is inefficient. The efficient alternative is to do
dma_map_sg() and use kmap_atomic() in the interrupt routine where we do
the PIO cleanup---I'm afraid I just passed on explaining how to do
this ... unless you care to do the honours ?
James
next prev parent reply other threads:[~2005-03-16 15:13 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200503160209.j2G29cAf010870@hera.kernel.org>
2005-03-16 7:58 ` [PATCH] dc395x: Fix support for highmem Jens Axboe
2005-03-16 15:13 ` James Bottomley [this message]
2005-03-16 16:04 ` Jens Axboe
2005-03-16 16:48 ` Matthew Wilcox
2005-03-16 16:53 ` Jens Axboe
2005-03-16 17:02 ` Christoph Hellwig
2005-03-16 17:04 ` Jens Axboe
2005-03-16 18:44 ` Mike Christie
2005-03-16 18:53 ` iSCSI and scatterlists Matthew Wilcox
2005-03-16 19:59 ` Dmitry Yusupov
2005-03-16 18:53 ` [PATCH] dc395x: Fix support for highmem Jens Axboe
2005-03-20 9:14 ` Christoph Hellwig
2005-03-20 20:51 ` Guennadi Liakhovetski
2005-03-21 7:55 ` Jens Axboe
[not found] ` <7044.1111398919@www16.gmx.net>
2005-03-21 10:38 ` gl
2005-03-21 10:44 ` Jens Axboe
2005-03-21 11:00 ` gl
2005-03-30 21:22 ` Guennadi Liakhovetski
2005-03-30 22:13 ` James Bottomley
2005-03-31 8:58 ` gl
2005-04-09 22:48 ` Guennadi Liakhovetski
2005-04-21 21:49 ` Guennadi Liakhovetski
2005-04-22 11:36 ` Jens Axboe
2005-04-23 9:35 ` Guennadi Liakhovetski
2005-04-23 10:06 ` Guennadi Liakhovetski
2005-04-23 19:01 ` James Bottomley
2005-04-24 0:22 ` Guennadi Liakhovetski
2005-04-24 14:31 ` Guennadi Liakhovetski
2005-04-24 22:11 ` James Bottomley
2005-04-25 19:56 ` Guennadi Liakhovetski
2005-03-16 20:24 ` Guennadi Liakhovetski
2005-03-17 7:40 ` Jens Axboe
[not found] ` <22734.1111050528@www13.gmx.net>
2005-03-17 9:41 ` gl
2005-03-17 10:08 ` Jens Axboe
2005-03-17 10:56 ` gl
2005-03-17 20:51 ` Guennadi Liakhovetski
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