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

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Message-ID: <56798826.6000908@fb.com>
Date:	Tue, 22 Dec 2015 10:28:06 -0700
From:	Jens Axboe <axboe@...com>
To:	Junichi Nomura <j-nomura@...jp.nec.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Tejun Heo <tj@...nel.org>
CC:	"Artem S. Tashkinov" <t.artem@...os.com>,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Christoph Hellwig <hch@....de>,
	Ming Lin <ming.l@....samsung.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 12/21/2015 10:26 PM, 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.

Good catch! The blk-mq parts aren't affected by this, the screw up only 
happened in the old IO path. I've added this with the appropriate 
tested-by from Artem, and CC stable and listed the commit that broke it:

commit 54efd50bfd873e2dbf784e0b21a8027ba4299a3e
Author: Kent Overstreet <kent.overstreet@...il.com>
Date:   Thu Apr 23 22:37:18 2015 -0700

     block: make generic_make_request handle arbitrarily sized bios

Thanks to all involved in nailing this down, it'll go out shortly.

-- 
Jens Axboe

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