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Subject: Re: [PATCH v2] nbd: replace kill_bdev() with __invalidate_device()
 again
To:     SunKe <sunke32@huawei.com>, <josef@toxicpanda.com>,
        <axboe@kernel.dk>, <linux-block@vger.kernel.org>,
        <nbd@other.debian.org>, <linux-kernel@vger.kernel.org>,
        <manoj.br@gmail.com>, <stable@vger.kernel.org>, <dwmw@amazon.com>
References: <1564575190-132357-1-git-send-email-sunke32@huawei.com>
From:   Munehisa Kamata <kamatam@amazon.com>
Message-ID: <98ac17cf-c658-9e80-8505-4309805fc1f0@amazon.com>
Date:   Wed, 31 Jul 2019 16:38:33 -0700
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On 7/31/2019 5:13 AM, SunKe wrote:
> From: Munehisa Kamata <kamatam@amazon.com>
> 
> Commit abbbdf12497d ("replace kill_bdev() with __invalidate_device()")
> once did this, but 29eaadc03649 ("nbd: stop using the bdev everywhere")
> resurrected kill_bdev() and it has been there since then. So buffer_head
> mappings still get killed on a server disconnection, and we can still
> hit the BUG_ON on a filesystem on the top of the nbd device.
> 
>   EXT4-fs (nbd0): mounted filesystem with ordered data mode. Opts: (null)
>   block nbd0: Receive control failed (result -32)
>   block nbd0: shutting down sockets
>   print_req_error: I/O error, dev nbd0, sector 66264 flags 3000
>   EXT4-fs warning (device nbd0): htree_dirblock_to_tree:979: inode #2: lblock 0: comm ls: error -5 reading directory block
>   print_req_error: I/O error, dev nbd0, sector 2264 flags 3000
>   EXT4-fs error (device nbd0): __ext4_get_inode_loc:4690: inode #2: block 283: comm ls: unable to read itable block
>   EXT4-fs error (device nbd0) in ext4_reserve_inode_write:5894: IO failure
>   ------------[ cut here ]------------
>   kernel BUG at fs/buffer.c:3057!
>   invalid opcode: 0000 [#1] SMP PTI
>   CPU: 7 PID: 40045 Comm: jbd2/nbd0-8 Not tainted 5.1.0-rc3+ #4
>   Hardware name: Amazon EC2 m5.12xlarge/, BIOS 1.0 10/16/2017
>   RIP: 0010:submit_bh_wbc+0x18b/0x190
>   ...
>   Call Trace:
>    jbd2_write_superblock+0xf1/0x230 [jbd2]
>    ? account_entity_enqueue+0xc5/0xf0
>    jbd2_journal_update_sb_log_tail+0x94/0xe0 [jbd2]
>    jbd2_journal_commit_transaction+0x12f/0x1d20 [jbd2]
>    ? __switch_to_asm+0x40/0x70
>    ...
>    ? lock_timer_base+0x67/0x80
>    kjournald2+0x121/0x360 [jbd2]
>    ? remove_wait_queue+0x60/0x60
>    kthread+0xf8/0x130
>    ? commit_timeout+0x10/0x10 [jbd2]
>    ? kthread_bind+0x10/0x10
>    ret_from_fork+0x35/0x40
> 
> With __invalidate_device(), I no longer hit the BUG_ON with sync or
> unmount on the disconnected device.
> 
> Fixes: 29eaadc03649 ("nbd: stop using the bdev everywhere")
> Cc: linux-block@vger.kernel.org
> Cc: Ratna Manoj Bolla <manoj.br@gmail.com>
> Cc: nbd@other.debian.org
> Cc: stable@vger.kernel.org
> Cc: David Woodhouse <dwmw@amazon.com>
> Signed-off-by: Munehisa Kamata <kamatam@amazon.com>
> 
> ---
> I reproduced this phenomenon on the fat file system.
> reproduce steps :
> 1.Establish a nbd connection.
> 2.Run two threads:one do mount and umount,anther one do clear_sock ioctl
> 3.Then hit the BUG_ON.
> 
> v2: Delete a link.
> 
> Signed-off-by: SunKe <sunke32@huawei.com>
> 
>  drivers/block/nbd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 9bcde23..e21d2de 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1231,7 +1231,7 @@ static void nbd_clear_sock_ioctl(struct nbd_device *nbd,
>  				 struct block_device *bdev)
>  {
>  	sock_shutdown(nbd);
> -	kill_bdev(bdev);
> +	__invalidate_device(bdev, true);
>  	nbd_bdev_reset(bdev);
>  	if (test_and_clear_bit(NBD_HAS_CONFIG_REF,
>  			       &nbd->config->runtime_flags))
> 

Hi SunKe,

I accidentally included the link in the original one. Sorry about that and thanks
for picking this up.

Regards,
Munehsia