Re: [PATCH] btrfs-progs: make 'btrfs replace' signal-handling works.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message --------
Subject: Re: [PATCH] btrfs-progs: make 'btrfs replace' signal-handling 
works.
From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Date: 2014年09月02日 19:25
> On Wed, Aug 06, 2014 at 09:17:07AM +0800, Qu Wenruo wrote:
>> Current BTRFS_IOC_DEV_REPLACE ioctl is synchronous, and during the ioctl
>> program is fallen into kernel and unable to handle signal, the original
>> signal function will never be executed until the dev replace is done.
>> This is very annoying for someone who wants to stop dev replace by
>> Ctrl-c (we have to admit that's the most users will do when replacing
>> dev with nodatacow/nodatasum mount option).
>>
>> This patch will create a thread to do the ioctl things, making the main
>> thread able to handle signal correctly.
> As described under the kernel patch, I'd like to use the respective
> cancel ioctls instead of signals.
I think I didn't describe it clear in the patch, the patch still uses 
cancel ioctl to cancel the dev-replace,
it just makes the original dev_replace_handle_sigint() function get 
called correctly.
(Before the patch, it will only be called after the ioctl is done, not 
when Ctrl-C is pressed, as explained in patch)

If you mean 'dev-replace cancel' is correct way Ctrl-C should not be 
used, then I can only agree with the first half.
Ctrl-C is almost a conditioned response for most people if they want to 
stop some program,
due to the principle of least astonishment, I think the SIGINT handling 
is still useful for most sysadmin.

Thanks,
Qu