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From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH] null_blk: poll queue support
Date: Mon, 3 May 2021 08:47:01 -0700
Message-ID: <725ea863-c754-addf-f143-71d7e2f273de@acm.org> (raw)
In-Reply-To: <baca710d-0f2a-16e2-60bd-b105b854e0ae@kernel.dk>

On 4/17/21 8:29 AM, Jens Axboe wrote:
> There's currently no way to experiment with polled IO with null_blk,
> which seems like an oversight. This patch adds support for polled IO.
> We keep a list of issued IOs on submit, and then process that list
> when mq_ops->poll() is invoked.
> 
> A new parameter is added, poll_queues. It defaults to 1 like the
> submit queues, meaning we'll have 1 poll queue available.

Has anyone run blktests against blk-for-next since this patch got
queued? The following appears in the kernel log if I run blktests:

root[5563]: run blktests block/010
null_blk: module loaded
==================================================================
BUG: KASAN: null-ptr-deref in null_map_queues+0x131/0x1a0 [null_blk]
Read of size 8 at addr 0000000000000000 by task modprobe/5612

CPU: 7 PID: 5612 Comm: modprobe Not tainted 5.12.0-dbg+ #33
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014
Call Trace:
 show_stack+0x52/0x58
 dump_stack+0x9d/0xcf
 kasan_report.cold+0x4b/0x50
 __asan_load8+0x69/0x90
 null_map_queues+0x131/0x1a0 [null_blk]
 blk_mq_update_queue_map+0x122/0x1a0
 blk_mq_alloc_tag_set+0x1c8/0x480
 null_init_tag_set+0x19c/0x220 [null_blk]
 null_init+0x1ac/0x1000 [null_blk]
 do_one_initcall+0xd3/0x460
 do_init_module+0x10a/0x400
 load_module+0xbe2/0xc50
 __do_sys_finit_module+0x131/0x1c0
 __x64_sys_finit_module+0x43/0x50
 do_syscall_64+0x3a/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f51f7fd367d
Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d bb f7 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd4a668728 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 00005609718ddbe0 RCX: 00007f51f7fd367d
RDX: 0000000000000000 RSI: 00005609718ddfe0 RDI: 0000000000000003
RBP: 0000000000040000 R08: 0000000000000000 R09: 000000000000003a
R10: 0000000000000003 R11: 0000000000000246 R12: 00005609718ddfe0
R13: 0000000000000000 R14: 00005609718ddd70 R15: 00005609718ddbe0
==================================================================

Thanks,

Bart.

  parent reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-17 15:29 Jens Axboe
2021-04-18  4:48 ` Chaitanya Kulkarni
2021-04-18  4:49 ` Chaitanya Kulkarni
2021-04-19 19:48   ` Jens Axboe
2021-04-19 22:19     ` Chaitanya Kulkarni
2021-04-19 22:55       ` Jens Axboe
2021-05-03 15:47 ` Bart Van Assche [this message]
2021-05-03 17:42   ` Jens Axboe
2021-05-04  0:32     ` Bart Van Assche

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