From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: mgorman@techsingularity.net, 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 1/2] fs: ext4: use BUG_ON if writepage call comes from direct reclaim
Date: Tue, 3 Jul 2018 19:43:31 -0400 [thread overview]
Message-ID: <20180703234331.GA5104@thunk.org> (raw)
In-Reply-To: <6c305241-d502-b8ea-a187-54c33e4ca692@linux.alibaba.com>
On Tue, Jul 03, 2018 at 10:05:04AM -0700, Yang Shi wrote:
> I'm not sure if it is a good choice to let filesystem handle such vital VM
> regression. IMHO, writing out filesystem page from direct reclaim context is
> a vital VM bug. It means something is definitely wrong in VM. It should
> never happen.
If it does happen, it should happen reliably; this isn't the sort of
thing where some linked list had gotten corrupted. This would be a
structural problem in the VM code.
So presumably, if the WARN_ON triggered, it should be be noticed by VM
developers, and they should fix it.
In general, though, BUG_ON's should be avoided unless there really is
no way to recover.
> It sounds ok to have filesystem throw out warning and handle it, but I'm not
> sure if someone will just ignore the warning, but it should *never* be
> ignored.
If a kernel develper (a VM developer in this case) ignores a warning,
that's just simply professional malpractice. In general WARN_ON's
should only be used as a sign of a kernel bug. So they should never
be ignored.
- Ted
next prev parent reply other threads:[~2018-07-03 23:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-03 4:11 [PATCH 1/2] fs: ext4: use BUG_ON if writepage call comes from direct reclaim Yang Shi
2018-07-03 4:11 ` [PATCH 2/2] fs: xfs: " Yang Shi
2018-07-03 4:37 ` Dave Chinner
2018-07-03 17:19 ` Darrick J. Wong
2018-07-03 10:39 ` [PATCH 1/2] fs: ext4: " Theodore Y. Ts'o
2018-07-03 17:05 ` Yang Shi
2018-07-03 23:10 ` Yang Shi
2018-07-03 23:43 ` Theodore Y. Ts'o [this message]
2018-07-04 14:03 ` Michal Hocko
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