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

From: Artem S. Tashkinov
Date: Sun Dec 20 2015 - 22:37:52 EST


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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