Re: [PATCH 2/2] fs: Make write(2) interruptible by a signal

[Wu Fengguang <fengguang.wu@intel.com>]

Jan,

Due to the (very low) possibility of data loss by partial writes, IMHO
it would safer to test this patch in linux-next until next merge window,
would you agree?

Pushing the first patch will address the main problem, anyway.

Thanks,
Fengguang

On Wed, Nov 16, 2011 at 07:12:15PM +0800, Jan Kara wrote:
> Currently write(2) to a file is not interruptible by a signal. Sometimes this
> is desirable (e.g. when you want to quickly kill a process hogging your disk or
> when some process gets blocked in balance_dirty_pages() indefinitely due to a
> filesystem being in an error condition).
> 
> Reported-by: Kazuya Mio <k-mio@sx.jp.nec.com>
> Tested-by: Kazuya Mio <k-mio@sx.jp.nec.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  mm/filemap.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c0018f2..c106d3b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2407,7 +2407,6 @@ static ssize_t generic_perform_write(struct file *file,
>  						iov_iter_count(i));
>  
>  again:
> -
>  		/*
>  		 * Bring in the user page that we will copy from _first_.
>  		 * Otherwise there's a nasty deadlock on copying from the
> @@ -2463,7 +2462,10 @@ again:
>  		written += copied;
>  
>  		balance_dirty_pages_ratelimited(mapping);
> -
> +		if (fatal_signal_pending(current)) {
> +			status = -EINTR;
> +			break;
> +		}
>  	} while (iov_iter_count(i));
>  
>  	return written ? written : status;
> -- 
> 1.7.1