From: Jeff Garzik <jgarzik@pobox.com>
To: Mark Lord <liml@rtr.ca>
Cc: Jens Axboe <axboe@suse.de>,
IDE/ATA development list <linux-ide@vger.kernel.org>
Subject: Re: libata+SGIO: is .dma_boundary respected?
Date: Sun, 19 Mar 2006 16:14:51 -0500 [thread overview]
Message-ID: <441DC9CB.7030203@pobox.com> (raw)
In-Reply-To: <441DC397.9040504@rtr.ca>
Mark Lord wrote:
> Jens / Jeff,
>
> Each libata driver registers a .dma_boundary field with SCSI.
> This field is used to prevent merging of bio segments across
> a hardware limitation boundary, usually 0xffff.
>
> This looks like it works for regular block I/O,
> but I'm not so sure about SGIO originated requests.
>
> Any thoughts, or code you can point me to?
Everything goes through the block layer, including SG_IO, so everyone
agrees on the boundaries that must be respected.
scsi sets blk_queue_segment_boundary() then gets out of the way, for the
most part. BIOVEC_SEG_BOUNDARY() is the macro that accesses this.
Trace back and forth from there. You will probably run into a call to
blk_recount_segments() in __bio_add_page(), or maybe you'll check the
seg boundary from another path.
Jeff
next prev parent reply other threads:[~2006-03-19 21:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-19 20:48 libata+SGIO: is .dma_boundary respected? Mark Lord
2006-03-19 21:14 ` Jeff Garzik [this message]
2006-03-19 21:19 ` Mark Lord
2006-03-19 21:38 ` Jeff Garzik
2006-03-19 21:45 ` Mark Lord
2006-03-19 21:54 ` Mark Lord
2006-03-21 1:18 ` Jeff Garzik
2006-03-21 4:43 ` Mark Lord
2006-03-21 6:14 ` Jeff Garzik
2006-03-21 13:59 ` Mark Lord
2006-03-21 18:42 ` Jens Axboe
2006-03-21 19:18 ` Mark Lord
2006-03-21 19:29 ` Jeff Garzik
2006-03-21 19:31 ` Mark Lord
2006-03-21 19:33 ` Mark Lord
2006-03-21 19:35 ` Jens Axboe
2006-03-21 19:38 ` Jeff Garzik
2006-03-21 19:42 ` Jens Axboe
2006-03-21 19:43 ` James Bottomley
2006-03-21 19:46 ` Jens Axboe
2006-03-21 20:44 ` James Bottomley
2006-03-21 21:54 ` Benjamin Herrenschmidt
2006-03-21 19:31 ` Jens Axboe
2006-03-21 19:36 ` Mark Lord
2006-03-21 19:43 ` Jeff Garzik
2006-03-21 20:51 ` Mark Lord
2006-03-22 11:25 ` Tejun Heo
2006-03-22 14:52 ` Mark Lord
2006-03-21 1:15 ` Jeff Garzik
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