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

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Message-ID: <20151222053710.GA26544@kmo-pixel>
Date:	Mon, 21 Dec 2015 20:37:10 -0900
From:	Kent Overstreet <kent.overstreet@...il.com>
To:	Junichi Nomura <j-nomura@...jp.nec.com>
Cc:	Tejun Heo <tj@...nel.org>,
	"Artem S. Tashkinov" <t.artem@...os.com>,
	"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 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?

Shit, you nailed it. Can't believe I didn't think to check that.

> 
> -- 
> Jun'ichi Nomura, NEC Corporation
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 5131993b..1d1c3c7 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1689,8 +1689,6 @@ static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
>  	struct request *req;
>  	unsigned int request_count = 0;
>  
> -	blk_queue_split(q, &bio, q->bio_split);
> -
>  	/*
>  	 * low level driver can indicate that it wants pages above a
>  	 * certain limit bounced to low memory (ie for highmem, or even
> @@ -1698,6 +1696,8 @@ static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
>  	 */
>  	blk_queue_bounce(q, &bio);
>  
> +	blk_queue_split(q, &bio, q->bio_split);
> +
>  	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
>  		bio->bi_error = -EIO;
>  		bio_endio(bio);
--
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