Date: Sun, 10 Oct 2004 10:14:16 +0200
From: Jens Axboe <axboe@suse.de>
To: "Adam J. Richter" <adam@yggdrasil.com>
Cc: linux-kernel@vger.kernel.org, dm-crypt@saout.de
Subject: Re: [PATCH?] make __bio_add_page check q->max_hw_sectors
Message-ID: <20041010081412.GA14636@suse.de>
References: <20041010115004.A5282@freya>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20041010115004.A5282@freya>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1526
Lines: 44

On Sun, Oct 10 2004, Adam J. Richter wrote:
> 	On an dm-crypt partiton on an IDE disk, 2.6.9-rc3 and
> 2.6.9-rc3-bk9 repeatedly generate the following error, which
> does not occur in 2.6.9-rc1:
> 
> 	bio too big for device dm-0 (256 > 255)
> 
> 	The stack trace looked something like this:
> 
> submit_bio
> mpage_bio_submit
> mpage_readpages
> readpages
> do_page_cache_readahead
> filemap_nopage
> do_no_page
> handle_mm_fault
> 
> 	Around 2.6.9-rc3, a new field q->max_hw_sectors was
> added to struct request_queue.  I was able to make this
> problem disappear by the following patch, which adds a
> check of this new field to __bio_add_page.  (I've edited
> this patch to hide other differences in my fs/bio.c, so
> it may be necessary to apply it by hand if patch fails.)
> 
> 	I do not understand the intended difference between
> the new max_hw_sectors field and max_sectors, so it is unclear
> to me if it is a bug that my dm-crypt request_queue has
> q->max_hw_sectors < q->max_sectors.  If q->max_hw_sectors
> is supposed to be guaranteed to be greater than or equal
> to q->max_sectors, then the real bug is elsewhere and my
> patch is unnecessary.

That's exactly correct, ->max_sectors must never be bigger than
max_hw_sectors, that is the real bug.

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/