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

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Date:   Sat, 12 Nov 2022 16:28:13 +0800
From:   Ye Bin <yebin@...weicloud.com>
To:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     ming.lei@...hat.com, Ye Bin <yebin10@...wei.com>
Subject: [PATCH -next] blk-mq: fix warning when unregister mq sysfs

From: Ye Bin <yebin10@...wei.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@...wei.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