Re: IO errors after "block: remove bio_get_nr_vecs()"

[Artem S. Tashkinov]

On 2015-12-21 08:21, Ming Lei wrote:
> On Mon, Dec 21, 2015 at 10:25 AM, Artem S. Tashkinov 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.

Um, sorry, what exact variables/files do you want to see? I'm not an 
expert in /sys.

> On Mon, Dec 21, 2015 at 10:32 AM, Kent Overstreet 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.

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