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

[Ming Lei]

On Mon, Dec 21, 2015 at 10:25 AM, Artem S. Tashkinov <t.artem@xxxxxxxxx> 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@xxxxxxxxx> 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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