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

[Jan Kara <jack@suse.cz>]

On Wed 16-11-11 19:44:21, Wu Fengguang wrote:
> 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?
  Fine with me. Thanks.

> Pushing the first patch will address the main problem, anyway.
  Hopefully, yes.

									Honza

> 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
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR