linux-kernel - Re: IO errors after "block: remove bio_get_nr

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Date:	Mon, 21 Dec 2015 20:55:10 -0900
From:	Kent Overstreet <kent.overstreet@...il.com>
To:	"Artem S. Tashkinov" <t.artem@...os.com>
Cc:	Junichi Nomura <j-nomura@...jp.nec.com>, Tejun Heo <tj@...nel.org>,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Christoph Hellwig <hch@....de>,
	Ming Lin <ming.l@....samsung.com>, Jens Axboe <axboe@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Whitehouse <swhiteho@...hat.com>,
	IDE-ML <linux-ide@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ming Lei <tom.leiming@...il.com>
Subject: Re: IO errors after "block: remove bio_get_nr_vecs()"

On Tue, Dec 22, 2015 at 10:52:37AM +0500, Artem S. Tashkinov wrote:
> On 2015-12-22 10:38, Kent Overstreet wrote:
> >On Tue, Dec 22, 2015 at 05:26:12AM +0000, Junichi Nomura wrote:
> >>On 12/22/15 12:59, Kent Overstreet wrote:
> >>> reproduced it with 32 bit pae:
> >>>
> >>>> 1. Exclude memory above 4G line with boot param "max_addr=4G".
> >>>
> >>> doesn't work - max_addr=1G doesn't work either
> >>>
> >>>> 2. Disable highmem with "highmem=0".
> >>>
> >>> works!
> >>>
> >>>> 3. Try booting 64bit kernel.
> >>>
> >>> works
> >>
> >>blk_queue_bio() does split then bounce, which makes the segment
> >>counting based on pages before bouncing and could go wrong.
> >>
> >>What do you think of a patch like this?
> >
> >Artem, can you give this patch a try?
> 
> 
> This patch ostensibly fixes the issue - at least I cannot immediately
> reproduce it. You can count me in as "Tested-by: Artem S. Tashkinov"

Let's all contemplate the fact that blk_segment_map_sg() _overrunning the end of
the provided sglist_ was this much of a clusterfuck to debug.
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