[PATCH -next] blk-mq: fix warning when unregister mq sysfs

Ye Bin
2022-11-12T08:07:03Z

From: Ye Bin <yebin10@huawei.com>

There's issue as follows when do fault injection test:
------------[ cut here ]------------
kernfs: can not remove 'nr_tags', no directory
WARNING: CPU: 8 PID: 2308 at fs/kernfs/dir.c:1635 kernfs_remove_by_name_ns+0xdd/0x100
Modules linked in: null_blk(-)
CPU: 8 PID: 2308 Comm: rmmod Not tainted 6.1.0-rc4-next-20221111+ #131
RIP: 0010:kernfs_remove_by_name_ns+0xdd/0x100
RSP: 0018:ffff88812149fbc8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffffffffb8137508 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffffb6b49ae0 RDI: ffffed1024293f6b
RBP: ffffffffb8137600 R08: 0000000000000001 R09: ffffed1024293f3d
R10: ffff88812149f9e7 R11: ffffed1024293f3c R12: 0000000000000000
R13: ffffffffb6b2d2a0 R14: ffffffffb6b2d1e0 R15: ffff88822f7f14b8
FS: 00007f97eacb9740(0000) GS:ffff8883ace00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f97e9b72b81 CR3: 000000022fbda000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
remove_files.isra.0+0x6c/0x170
sysfs_remove_group+0x9b/0x180
sysfs_remove_groups+0x4f/0xa0
__kobject_del+0x7d/0x1d0
kobject_del+0x32/0x50
blk_mq_sysfs_unregister.cold+0x8/0xd
blk_unregister_queue+0xed/0x260
del_gendisk+0x27e/0x900
null_del_dev.part.0+0x166/0x510 [null_blk]
null_destroy_dev+0x37/0x5c [null_blk]
null_exit+0x4c/0x9d [null_blk]
__do_sys_delete_module.isra.0+0x2f3/0x520
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
</TASK>

Fault injection context as follows:
kobject_add
blk_mq_register_hctx
blk_mq_sysfs_register
blk_register_queue
device_add_disk
null_add_dev.part.0 [null_blk]

As 'blk_mq_sysfs_register' may failed, but when unregister mq sysfs don't
judge sysfs if registered. 'blk_mq_sysfs_register' also didn't handle
error correctly.
To solve above issue, if sysfs is unregstered just exit.

Signed-off-by: Ye Bin <yebin10@huawei.com>
---
block/blk-mq-sysfs.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 93997d297d42..0cda0a729f3c 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -185,7 +185,7 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx)
{
struct request_queue *q = hctx->queue;
struct blk_mq_ctx *ctx;
- int i, ret;
+ int i, j, ret;

if (!hctx->nr_ctx)
return 0;
@@ -197,9 +197,16 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx)
hctx_for_each_ctx(hctx, ctx, i) {
ret = kobject_add(&ctx->kobj, &hctx->kobj, "cpu%u", ctx->cpu);
if (ret)
- break;
+ goto out;
}

+ return 0;
+out:
+ hctx_for_each_ctx(hctx, ctx, j) {
+ if (j < i)
+ kobject_del(&ctx->kobj);
+ }
+ kobject_del(&hctx->kobj);
return ret;
}

@@ -278,6 +285,8 @@ void blk_mq_sysfs_unregister(struct gendisk *disk)
struct blk_mq_hw_ctx *hctx;
unsigned long i;

+ if (!q->mq_sysfs_init_done)
+ return;
lockdep_assert_held(&q->sysfs_dir_lock);

queue_for_each_hw_ctx(q, hctx, i)
--
2.31.1