linux-kernel - Re: [PATCH] sysfs: replace WARN() with pr_debug in sysfs_remove

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Date:   Tue, 1 Aug 2017 11:06:35 -0700
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Ethan Zhao <ethan.zhao@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        ethan.kernel@...il.com
Subject: Re: [PATCH] sysfs: replace WARN() with pr_debug in
 sysfs_remove_group()

On Tue, Aug 01, 2017 at 05:02:25PM +0900, Ethan Zhao wrote:
> There is no enough error handling in block device adding/registration
> path, for example,
> 
> device_add_disk()
>   blk_register_queue()
> 
> When kernel returns from device_add_disk(), no return value to tell
> us it was successful or not --- that suggests it would always succeed,
> and according to this assumption, then during block device removal/
> unregistration steps,
> 
> sd_remove()
>   del_gendisk()
>     blk_unregister_queue()
> 
> dpm_sysfs_remove(), blk_trace_remove_sysfs() will be called blindly,
> though there is likely no 'trace' 'power' sysfs groups there because
> actually blk_register_queue()/device_add() failed somewhere. thus
> causes WARN flood emitted from sysfs_remove_group() as following triggered
> by unloading fnic driver:

Then fix the real issue here, don't paper over the issue by changing the
sysfs core please.  No other subsystem seems to be having this issue.

thanks,

greg k-h