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

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Date:	Tue, 22 Dec 2015 06:51:27 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Artem S. Tashkinov" <t.artem@...os.com>,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Kent Overstreet <kent.overstreet@...il.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>
Subject: Re: IO errors after "block: remove bio_get_nr_vecs()"

On Tue, Dec 22, 2015 at 3:35 AM, Tejun Heo <tj@...nel.org> wrote:
>
>> [   74.367632] XXX cmd=ee9e0260 cmd_tbl=ee9ed600 ahci_sg=ee9ed680
>> [   74.367634] XXX opts=140005 st=0 addr=2e9ed600 addr_hi=0 rsvd=0:0:0:0
>> [   74.367637] XXX fis=00608027:40218900:07000004:08000098 00000000:00000000:00000000:00001fff
>> [   74.367639] XXX qc->n_elem=20 fis_len=5 prdtl=20
>> [   74.367641] XXX sg[0] = 29007000 0 8fff (36864)
>> [   74.367643] XXX sg[1] = 29218000 0 7fff (32768)
>> [   74.367645] XXX sg[2] = 29298000 0 7fff (32768)
>> [   74.367646] XXX sg[3] = 29ad8000 0 7fff (32768)
>> [   74.367648] XXX sg[4] = 29338000 0 7fff (32768)
>> [   74.367650] XXX sg[5] = 29370000 0 2fff (12288)
>> [   74.367652] XXX sg[6] = 219000 0 2fff (12288)
>> [   74.367653] XXX sg[7] = 230000 0 3fff (16384)
>> [   74.367655] XXX sg[8] = 29373000 0 4fff (20480)
>> [   74.367657] XXX sg[9] = 29130000 0 ffff (65536)
>> [   74.367659] XXX sg[10] = 29170000 0 ffff (65536)
>> [   74.367660] XXX sg[11] = 29280000 0 ffff (65536)
>> [   74.367662] XXX sg[12] = 29200000 0 ffff (65536)
>> [   74.367664] XXX sg[13] = 29320000 0 ffff (65536)
>> [   74.367666] XXX sg[14] = 29360000 0 ffff (65536)
>> [   74.367667] XXX sg[15] = 29340000 0 ffff (65536)
>> [   74.367669] XXX sg[16] = 29350000 0 ffff (65536)
>> [   74.367671] XXX sg[17] = 29300000 0 ffff (65536)
>> [   74.367672] XXX sg[18] = 29310000 0 ffff (65536)
>> [   74.367674] XXX sg[19] = 29020000 0 7fff (32768)
>
> And everything checks out.  Data lenghts are consistent and all the
> addresses look kosher - at least nothing should upset the data
> transfer itself.

Maybe we can check more, such as if the sg element is correctly
merged from bvec, and the following code should be useful to check
that:

+static void ahci_dump_req(struct ata_queued_cmd *qc)
+{
+       struct scsi_cmnd *cmd = qc->scsicmd;
+       struct request *req = cmd->request;
+       struct req_iterator iter;
+       struct bio_vec bv;
+       int i = 0;
+       phys_addr_t paddr;
+
+       printk("%s: \n", __func__);
+       rq_for_each_segment(bv, req, iter) {
+               paddr = page_to_phys(bv.bv_page);
+               printk("\t %3d: %x-%x %x %u\n", i++,
+                       (unsigned)paddr & 0xffffffff,
+                       (unsigned)(paddr >> 32),
+                       bv.bv_offset,
+                       bv.bv_len);
+       }
+}

Thanks,
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