On 11/20/18 10:21 AM, Ming Lei wrote:
> On Mon, Nov 19, 2018 at 12:51:26PM +0900, Damien Le Moal wrote:
>> bio->bi_ioc is never set so always NULL. Remove references to it in
>> bio_disassociate_task() and in rq_ioc() and delete this field from
>> struct bio. With this change, rq_ioc() always returns
>> current->io_context without the need for a bio argument. Further
>> simplify the code and make it more readable by also removing this
>> helper, which also allows to simplify blk_mq_sched_assign_ioc() by
>> removing its bio argument.
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
>> ---
>> block/bio.c | 4 ----
>> block/blk-core.c | 2 +-
>> block/blk-mq-sched.c | 4 ++--
>> block/blk-mq-sched.h | 2 +-
>> block/blk-mq.c | 4 ++--
>> block/blk.h | 16 ----------------
>> include/linux/blk_types.h | 3 +--
>> 7 files changed, 7 insertions(+), 28 deletions(-)
>>
>> diff --git a/block/bio.c b/block/bio.c
>> index 4f4d9884443b..03895cc0d74a 100644
>> --- a/block/bio.c
>> +++ b/block/bio.c
>> @@ -2027,10 +2027,6 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
>> */
>> void bio_disassociate_task(struct bio *bio)
>> {
>> - if (bio->bi_ioc) {
>> - put_io_context(bio->bi_ioc);
>> - bio->bi_ioc = NULL;
>> - }
>> if (bio->bi_css) {
>> css_put(bio->bi_css);
>> bio->bi_css = NULL;
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index d6e8ab9ca99d..492648c96992 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -813,7 +813,7 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
>>
>> void blk_init_request_from_bio(struct request *req, struct bio *bio)
>> {
>> - struct io_context *ioc = rq_ioc(bio);
>> + struct io_context *ioc = current->io_context;
>>
>> if (bio->bi_opf & REQ_RAHEAD)
>> req->cmd_flags |= REQ_FAILFAST_MASK;
>> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
>> index d084f731d104..13b8dc332541 100644
>> --- a/block/blk-mq-sched.c
>> +++ b/block/blk-mq-sched.c
>> @@ -31,10 +31,10 @@ void blk_mq_sched_free_hctx_data(struct request_queue *q,
>> }
>> EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
>>
>> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
>> +void blk_mq_sched_assign_ioc(struct request *rq)
>> {
>> struct request_queue *q = rq->q;
>> - struct io_context *ioc = rq_ioc(bio);
>> + struct io_context *ioc = current->io_context;
>> struct io_cq *icq;
>>
>> spin_lock_irq(&q->queue_lock);
>> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
>> index 7ff5671bf128..0f719c8532ae 100644
>> --- a/block/blk-mq-sched.h
>> +++ b/block/blk-mq-sched.h
>> @@ -8,7 +8,7 @@
>> void blk_mq_sched_free_hctx_data(struct request_queue *q,
>> void (*exit)(struct blk_mq_hw_ctx *));
>>
>> -void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio);
>> +void blk_mq_sched_assign_ioc(struct request *rq);
>>
>> void blk_mq_sched_request_inserted(struct request *rq);
>> bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 32b246ed44c0..636f80b96fa6 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -389,8 +389,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
>> if (!op_is_flush(data->cmd_flags)) {
>> rq->elv.icq = NULL;
>> if (e && e->type->ops.prepare_request) {
>> - if (e->type->icq_cache && rq_ioc(bio))
>> - blk_mq_sched_assign_ioc(rq, bio);
>> + if (e->type->icq_cache)
>> + blk_mq_sched_assign_ioc(rq);
>>
>> e->type->ops.prepare_request(rq, bio);
>> rq->rq_flags |= RQF_ELVPRIV;
>> diff --git a/block/blk.h b/block/blk.h
>> index 816a9abb87cd..610948157a5b 100644
>> --- a/block/blk.h
>> +++ b/block/blk.h
>> @@ -254,22 +254,6 @@ void ioc_clear_queue(struct request_queue *q);
>>
>> int create_task_io_context(struct task_struct *task, gfp_t gfp_mask, int node);
>>
>> -/**
>> - * rq_ioc - determine io_context for request allocation
>> - * @bio: request being allocated is for this bio (can be %NULL)
>> - *
>> - * Determine io_context to use for request allocation for @bio. May return
>> - * %NULL if %current->io_context doesn't exist.
>> - */
>> -static inline struct io_context *rq_ioc(struct bio *bio)
>> -{
>> -#ifdef CONFIG_BLK_CGROUP
>> - if (bio && bio->bi_ioc)
>> - return bio->bi_ioc;
>> -#endif
>> - return current->io_context;
>> -}
>> -
>> /**
>> * create_io_context - try to create task->io_context
>> * @gfp_mask: allocation mask
>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>> index dbdbfbd6a987..c0ba1a038ff3 100644
>> --- a/include/linux/blk_types.h
>> +++ b/include/linux/blk_types.h
>> @@ -174,10 +174,9 @@ struct bio {
>> void *bi_private;
>> #ifdef CONFIG_BLK_CGROUP
>> /*
>> - * Optional ioc and css associated with this bio. Put on bio
>> + * Optional css associated with this bio. Put on bio
>> * release. Read comment on top of bio_associate_current().
>> */
>> - struct io_context *bi_ioc;
>> struct cgroup_subsys_state *bi_css;
>> struct blkcg_gq *bi_blkg;
>> struct bio_issue bi_issue;
>
> Hi,
>
> Just found the following kernel oops, seems it is likely related with this
> patch.
>
> [ 391.981012] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
> [ 391.982506] PGD 0 P4D 0
> [ 391.982975] Oops: 0000 [#1] PREEMPT SMP PTI
> [ 391.983769] CPU: 1 PID: 1790 Comm: scsi_id Not tainted 4.20.0-rc3_72abead3bf43_for-4.21-block-mp-bvec-V11+ #1
> [ 391.985563] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
> [ 391.987107] RIP: 0010:ioc_lookup_icq+0x13/0x54
> [ 391.987936] Code: f6 48 8b 3d 1c 78 5b 01 5b 5d 41 5c 41 5d 41 5e 41 5f e9 68 bd eb ff 0f 1f 44 00 00 55 53 48 89 fb 51 48 89 f5 e8 e3 82 da ff <48> 8b 43 38 48 85 c0 74 05 48 39 28 74 22 48 63 b5 8c 00 00 00 48
> [ 391.991318] RSP: 0018:ffffc90001467bb0 EFLAGS: 00010002
> [ 391.992292] RAX: ffff888266c85ac0 RBX: 0000000000000000 RCX: 0000000000000100
> [ 391.993615] RDX: 0000000000000001 RSI: ffff88826601f230 RDI: 0000000000000000
> [ 391.994917] RBP: ffff88826601f230 R08: 00000000f461df07 R09: 0000000000000006
> [ 391.996242] R10: ffffc90001467b10 R11: 0000000000000020 R12: ffff888269df4000
> [ 391.997572] R13: 0000000000000000 R14: ffff88826601f2c4 R15: 0000000000000001
> [ 391.998905] FS: 00007fa6923b7940(0000) GS:ffff888277a80000(0000) knlGS:0000000000000000
> [ 392.000389] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 392.001468] CR2: 0000000000000038 CR3: 0000000106dd8005 CR4: 0000000000760ee0
> [ 392.002783] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 392.004108] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 392.005394] PKRU: 55555554
> [ 392.005897] Call Trace:
> [ 392.006384] blk_mq_sched_assign_ioc+0x3d/0x7f
> [ 392.007216] blk_mq_get_request+0x321/0x354
> [ 392.008008] blk_mq_alloc_request+0x4e/0xbf
> [ 392.008802] blk_get_request+0x24/0x4c
> [ 392.009518] sg_io+0x93/0x371
> [ 392.010074] ? bd_acquire+0xa6/0xa6
> [ 392.010707] ? dput+0x29/0xfd
> [ 392.011232] ? mntput_no_expire+0x11/0x185
> [ 392.011987] scsi_cmd_ioctl+0x1d3/0x386
> [ 392.012707] sd_ioctl+0xbb/0xde [sd_mod]
> [ 392.013449] blkdev_ioctl+0x893/0x8bf
> [ 392.014132] block_ioctl+0x3c/0x3f
> [ 392.014781] vfs_ioctl+0x1e/0x2b
> [ 392.015378] do_vfs_ioctl+0x531/0x559
> [ 392.016059] ksys_ioctl+0x3e/0x5d
> [ 392.016681] __x64_sys_ioctl+0x16/0x19
> [ 392.017361] do_syscall_64+0x84/0x13f
> [ 392.018060] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 392.018995] RIP: 0033:0x7fa691edf267
> [ 392.019663] Code: b3 66 90 48 8b 05 19 3c 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 3b 2c 00 f7 d8 64 89 01 48
> [ 392.023072] RSP: 002b:00007ffe463e8de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [ 392.024457] RAX: ffffffffffffffda RBX: 00007ffe463e8e20 RCX: 00007fa691edf267
> [ 392.025767] RDX: 00007ffe463e8e20 RSI: 0000000000002285 RDI: 0000000000000004
> [ 392.027068] RBP: 00007ffe463e9470 R08: 0000000000002006 R09: 00000000fffffe00
> [ 392.028413] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe463e9920
> [ 392.029722] R13: 00007ffe463e8e20 R14: 00007ffe463e8e2a R15: 00007ffe463e9920
> [ 392.031031] Modules linked in: scsi_debug null_blk isofs iTCO_wdt iTCO_vendor_support i2c_i801 i2c_core lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel virtio_scsi qemu_fw_cfg dm_mirror dm_region_hash dm_log dm_mod [last unloaded: null_blk]
> [ 392.035573] Dumping ftrace buffer:
> [ 392.036203] (ftrace buffer empty)
> [ 392.036871] CR2: 0000000000000038
> [ 392.037503] ---[ end trace fa20a1088b068790 ]---
I think the below should fix it, we haven't necessarily setup an
ioc if we're just doing as passthrough request.
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 13b8dc332541..f096d8989773 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -34,9 +34,16 @@ EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
void blk_mq_sched_assign_ioc(struct request *rq)
{
struct request_queue *q = rq->q;
- struct io_context *ioc = current->io_context;
+ struct io_context *ioc;
struct io_cq *icq;
+ /*
+ * May not have an IO context if it's a passthrough request
+ */
+ ioc = current->io_context;
+ if (!ioc)
+ return;
+
spin_lock_irq(&q->queue_lock);
icq = ioc_lookup_icq(ioc, q);
spin_unlock_irq(&q->queue_lock);
--
Jens Axboe
