On Mon, Jun 26, 2023 at 05:09:59PM +0800, Ferry Meng wrote:
Hello:
I'm testing the io-uring nvme passthrough via fio. But I have
encountered the following issue:
When I specify 'blocksize' exceeding 128KB (actually the maximum size
per request can send 'max_sectors_kb'), the creation of request failed
and directly returned -22 (-EINVAL).
For example:
# cat fio.job
[global]
ioengine=io_uring_cmd
thread=1
time_based
numjobs=1
iodepth=1
runtime=120
rw=randwrite
cmd_type=nvme
hipri=1
[randwrite]
bs=132k
filename=/dev/ng1n1
# fio fio.job
randwrite: (g=0): rw=randwrite, bs=(R) 132KiB-132KiB, (W)
132KiB-132KiB, (T) 132KiB-132KiB, ioengine=io_uring_cmd, iodepth=1
fio-3.34-10-g2fa0-dirty
Starting 1 thread
fio: io_u error on file /dev/ng1n1: Invalid argument: write
offset=231584956416, buflen=135168
fio: pid=148989, err=22/file:io_u.c:1889, func=io_u error,
error=Invalid argument
I tracked the position that returns the error val in kernel and dumped
calltrace.
[ 83.352715] nvme nvme1: 15/0/1 default/read/poll queues
[ 83.363273] nvme nvme1: Ignoring bogus Namespace Identifiers
[ 91.578457] CPU: 14 PID: 3993 Comm: fio Not tainted
6.4.0-rc7-00014-g692b7dc87ca6-dirty #2
[ 91.578462] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS
2221b89 04/01/2014
[ 91.578463] Call Trace:
[ 91.578476] <TASK>
[ 91.578478] dump_stack_lvl+0x36/0x50
[ 91.578484] ll_back_merge_fn+0x20d/0x320
[ 91.578490] blk_rq_append_bio+0x6d/0xc0
[ 91.578492] bio_map_user_iov+0x24a/0x3d0
[ 91.578494] blk_rq_map_user_iov+0x292/0x680
[ 91.578496] ? blk_mq_get_tag+0x249/0x280
[ 91.578500] blk_rq_map_user+0x56/0x80
[ 91.578503] nvme_map_user_request.isra.15+0x90/0x1e0 [nvme_core]
[ 91.578515] nvme_uring_cmd_io+0x29d/0x2f0 [nvme_core]
[ 91.578522] io_uring_cmd+0x89/0x110
[ 91.578526] ? __pfx_io_uring_cmd+0x10/0x10
[ 91.578528] io_issue_sqe+0x1e0/0x2d0
[ 91.578530] io_submit_sqes+0x1e3/0x650
[ 91.578532] __x64_sys_io_uring_enter+0x2da/0x450
[ 91.578534] do_syscall_64+0x3b/0x90
[ 91.578537] entry_SYSCALL_64_after_hwframe+0x72/0xdc
Here in bio_map_user_iov()->blk_rq_append_bio(), I found the error val
-EINVAL:
blk_rq_append_bio:
...
if (!ll_back_merge_fn(rq, bio, nr_segs))
return -EINVAL;
rq->biotail->bi_next = bio;
...
And in ll_back_merge_fn(), returns 0 if merge can't happen. It checks
the request size:
ll_back_merge_fn:
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
req_set_nomerge(req->q, req);
return 0;
}
The ROOT cause is: In blk_rq_get_max_sectors, it returns
'max_hw_sectors' directly(in my device ,it's 256 sector, which means
128KB), causing the above inequality to hold true.
blk_rq_get_max_sectors:
...
if (blk_rq_is_passthrough(rq)){
return q->limits.max_hw_sectors;
}
...
I checked my disk's specs(cat
/sys/block/<mydisk>/queue/max_hw_sectors_kb
/sys/block/<mydisk>/queue/max_sectors_kb), both are 128KB.So I think
this arg causing the issue.
I'm not sure if this is a designed restriction. Or should I have to
take care of it in application?
Right, passthrough interface does not abstract the device limits.
This needs to be handled in application.
