From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 3 Jul 2018 14:37:38 +1000 From: Dave Chinner To: Yang Shi Cc: mgorman@techsingularity.net, tytso@mit.edu, adilger.kernel@dilger.ca, darrick.wong@oracle.com, dchinner@redhat.com, akpm@linux-foundation.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] fs: xfs: use BUG_ON if writepage call comes from direct reclaim Message-ID: <20180703043738.GG2234@dastard> References: <1530591079-33813-1-git-send-email-yang.shi@linux.alibaba.com> <1530591079-33813-2-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1530591079-33813-2-git-send-email-yang.shi@linux.alibaba.com> Sender: owner-linux-mm@kvack.org List-ID: On Tue, Jul 03, 2018 at 12:11:19PM +0800, Yang Shi wrote: > direct reclaim doesn't write out filesystem page, only kswapd could do > this. So, if it is called from direct relaim, it is definitely a bug. > > And, Mel Gorman mentioned "Ultimately, this will be a BUG_ON." in commit > 94054fa3fca1fd78db02cb3d68d5627120f0a1d4 ("xfs: warn if direct reclaim > tries to writeback pages"), > > It has been many years since that commit, so it should be safe to > elevate WARN_ON to BUG_ON now. NACK. The existing code warns and then handles the situation gracefully - this is the appropriate way to handle incorrect calling contexts. There is absolutely no good reason to panic production kernels in situations like this. Cheers, Dave. -- Dave Chinner david@fromorbit.com