Re: kernel BUG at block/bio.c:1787! while initializing scsi_debug on ppc64 host

[Ming Lei <tom.leiming@gmail.com>]

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On Tue, Dec 15, 2015 at 9:06 PM, Eryu Guan <guaneryu@gmail.com> wrote:
> On Tue, Dec 15, 2015 at 08:06:47PM +0800, Ming Lei wrote:
>> On Tue, Dec 15, 2015 at 7:20 PM, Eryu Guan <guaneryu@gmail.com> wrote:
>> > On Fri, Dec 11, 2015 at 07:53:40PM +0800, Eryu Guan wrote:
>> >> Hi,
>> >>
>> >> I saw this kernel BUG_ON on 4.4-rc4 kernel, and this can be reproduced
>> >> easily on ppc64 host by:
>> >
>> > This is still reproducible with 4.4-rc5 kernel.
>>
>> Could you capture the debug log after appyling the attached patch and
>> the reproduction?
>
> Thanks for looking into this! dmesg shows:
>
> [  686.217682] bio_split: sectors 0, bio_sectors 128, bi_rw 0

Then I guess queue_max_sectors(q) is bad, could you apply the
attached patch(and the last patch) and post the log?


>
> Thanks,
> Eryu
>
> P.S. full call trace
>
> [  686.065692] scsi_debug:sdebug_driver_probe: host protection
> [  686.065710] scsi host1: scsi_debug, version 1.85 [20141022], dev_size_mb=256, opts=0x0
> [  686.065981] scsi 1:0:0:0: Direct-Access     Linux    scsi_debug       0184 PQ: 0 ANSI: 6
> [  686.066873] sd 1:0:0:0: Attached scsi generic sg1 type 0
> [  686.077683] sd 1:0:0:0: [sdb] 524288 512-byte logical blocks: (268 MB/256 MiB)
> [  686.077694] sd 1:0:0:0: [sdb] 4096-byte physical blocks
> [  686.087670] sd 1:0:0:0: [sdb] Write Protect is off
> [  686.107671] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA
> [  686.217682] bio_split: sectors 0, bio_sectors 128, bi_rw 0
> [  686.217695] ------------[ cut here ]------------
> [  686.217698] kernel BUG at block/bio.c:1793!
> [  686.217702] Oops: Exception in kernel mode, sig: 5 [#1]
> [  686.217704] SMP NR_CPUS=2048 NUMA pSeries
> [  686.217707] Modules linked in: scsi_debug sg pseries_rng nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod ibmvscsi ibmveth scsi_transport_srp
> [  686.217727] CPU: 8 PID: 9515 Comm: kworker/u32:0 Not tainted 4.4.0-rc5+ #33
> [  686.217733] Workqueue: events_unbound async_run_entry_fn
> [  686.217737] task: c0000005edb23cc0 ti: c0000005f016c000 task.ti: c0000005f016c000
> [  686.217740] NIP: c0000000003c45c4 LR: c0000000003c46b8 CTR: 00000000013abb8c
> [  686.217743] REGS: c0000005f016ea20 TRAP: 0700   Not tainted  (4.4.0-rc5+)
> [  686.217746] MSR: 8000000100029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 22bb2322  XER: 0000000f
> [  686.217756] CFAR: c0000000003c46cc SOFTE: 1
> GPR00: c0000000003c46b8 c0000005f016eca0 c000000001068300 000000000000002e
> GPR04: c0000005ffd09c50 c0000005ffd1b4a0 0000000000010000 0000000000000000
> GPR08: 0000000000000001 c000000000bab284 00000005ff160000 0000000000000130
> GPR12: 0000000000003f30 c00000000e7e4c00 0000000000000000 f0000000015d0e40
> GPR16: c0000005f3c3b7a0 c000000574390000 0000000000000001 0000000000000000
> GPR20: 0000000000000000 0000000000000080 0000000000000000 c0000005f5093200
> GPR24: c0000005edb0efa0 c0000005f016ee60 c0000005f5093288 0000000000000000
> GPR28: 0000000002400000 c0000005f5093200 0000000000000000 c0000005efd67600
> [  686.217797] NIP [c0000000003c45c4] bio_split+0x54/0x160
> [  686.217800] LR [c0000000003c46b8] bio_split+0x148/0x160
> [  686.217803] Call Trace:
> [  686.217805] [c0000005f016eca0] [c0000000003c46b8] bio_split+0x148/0x160 (unreliable)
> [  686.217810] [c0000005f016ed30] [c0000000003d75e0] blk_queue_split+0x3c0/0x570
> [  686.217814] [c0000005f016ee30] [c0000000003d10a8] blk_queue_bio+0x48/0x440
> [  686.217818] [c0000005f016ee90] [c0000000003cec9c] generic_make_request+0x15c/0x220
> [  686.217822] [c0000005f016eef0] [c0000000003cee24] submit_bio+0xc4/0x1d0
> [  686.217826] [c0000005f016efa0] [c0000000002db204] submit_bh_wbc+0x1a4/0x200
> [  686.217830] [c0000005f016eff0] [c0000000002db6f0] block_read_full_page+0x320/0x420
> [  686.217835] [c0000005f016f4a0] [c0000000002dedb4] blkdev_readpage+0x24/0x40
> [  686.217839] [c0000005f016f4c0] [c0000000001f06fc] do_read_cache_page+0xbc/0x290
> [  686.217844] [c0000005f016f530] [c0000000003e8e00] read_dev_sector+0x40/0xc0
> [  686.217848] [c0000005f016f560] [c0000000003ec6bc] read_lba+0xdc/0x200
> [  686.217851] [c0000005f016f5c0] [c0000000003ece4c] find_valid_gpt+0xec/0x740
> [  686.217855] [c0000005f016f6a0] [c0000000003ed894] efi_partition+0x3f4/0x450
> [  686.217859] [c0000005f016f820] [c0000000003ea428] check_partition+0x158/0x2f0
> [  686.217863] [c0000005f016f8a0] [c0000000003e9694] rescan_partitions+0xd4/0x390
> [  686.217867] [c0000005f016f970] [c0000000002e0938] __blkdev_get+0x3a8/0x4d0
> [  686.217871] [c0000005f016f9e0] [c0000000002e0c90] blkdev_get+0x230/0x4a0
> [  686.217875] [c0000005f016fa90] [c0000000003e65b8] add_disk+0x478/0x500
> [  686.217880] [c0000005f016fb40] [d000000003fa66a8] sd_probe_async+0xf8/0x240 [sd_mod]
> [  686.217884] [c0000005f016fbc0] [c0000000000d7db8] async_run_entry_fn+0x98/0x1f0
> [  686.217888] [c0000005f016fc50] [c0000000000cc1a0] process_one_work+0x190/0x470
> [  686.217892] [c0000005f016fce0] [c0000000000cc5fc] worker_thread+0x17c/0x5a0
> [  686.217896] [c0000005f016fd80] [c0000000000d3da8] kthread+0x108/0x130
> [  686.217901] [c0000005f016fe30] [c000000000009538] ret_from_kernel_thread+0x5c/0xa4
> [  686.217904] Instruction dump:
> [  686.217906] 7cdf3378 7c9e2378 7c7d1b78 f8010010 7cbc2b78 f821ff71 80c30028 40dd00e8
> [  686.217912] 54caba7e 39000000 7f8a2040 40dd00d8 <0b080000> 54c9ba7e 7bdb0020 7f89d840
> [  686.217921] ---[ end trace 80d38b6aaec5b2ff ]---



-- 
Ming Lei

[-- Attachment #2: blk-merge-dbg.patch --]
[-- Type: text/x-patch, Size: 502 bytes --]

diff --git a/block/blk-merge.c b/block/blk-merge.c
index b66f095..d0ea926 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -129,6 +129,15 @@ split:
 	*segs = nsegs;
 
 	if (do_split) {
+		if (!sectors) {
+			printk("%s: nseg %u, max_secs %u, max segs %u\n",
+				__func__, nsegs,
+				queue_max_sectors(q),
+				queue_max_segments(q));
+			printk("\t bv.len %u, bv.offset %u\n",
+					bv.bv_len, bv.bv_offset);
+		}
+
 		new = bio_split(bio, sectors, GFP_NOIO, bs);
 		if (new)
 			bio = new;