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

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Date:	Mon, 21 Dec 2015 11:21:35 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Kent Overstreet <kent.overstreet@...il.com>
Cc:	"Artem S. Tashkinov" <t.artem@...os.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@....de>,
	Ming Lin <ming.l@....samsung.com>, Jens Axboe <axboe@...com>,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Tejun Heo <tj@...nel.org>, IDE-ML <linux-ide@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: IO errors after "block: remove bio_get_nr_vecs()"

On Mon, Dec 21, 2015 at 10:25 AM, Artem S. Tashkinov <t.artem@...os.com> wrote:
> # cat
> /sys/block/sda/queue/{max_hw_sectors_kb,max_sectors_kb,max_segments,max_segment_size}
> 32767
> 32767
> 168
> 65536

Looks it is fine, then maybe it is related with BIOVEC_PHYS_MERGEABLE(),
BIOVEC_SEG_BOUNDARY() or sort of thing, because dma_addr_t and
phys_addr_t turn to 64-bit with PAE, but 'unsigned long' and 'void *'
is still 32bit.

It was confirmed that there isn't the issue if PAE is disabled.

Dumping both sata/ahci hw sg table and bio's bvec might be helpful.

On Mon, Dec 21, 2015 at 10:32 AM, Kent Overstreet
<kent.overstreet@...il.com> wrote:
>
> oy vey. WTF's been happening in blk-merge.c?
>
> Theyy're not the same bug. The bug in your thread was introduced by Jens in
> 5014c311ba "block: fix bogus compiler warnings in blk-merge.c", where he screwed
> up the bvprv handling - but that patch comes after the patch Artem bisected to.
>
> blk_bio_segment_split() looks correct in b54ffb73ca.

Yes, that is why reverting 578270bfb(block: fix segment split) can make the
issue disappear, because 5014c311ba "block: fix bogus compiler
warnings in blk-merge.c" basically disables sg-merge and prevents the
issue from being
triggered.



Thanks,
Ming Lei
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