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Date:   Thu, 19 Nov 2020 22:36:00 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     yebin <yebin10@...wei.com>, jack@...e.com,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH 0/2] Fix race between do_invalidatepage and
 init_page_buffers

On Tue, Aug 25, 2020 at 10:41:37AM +0200, Jan Kara wrote:
> On Tue 25-08-20 10:11:29, yebin wrote:
> > Your patch certainly can fix the problem with my testcases, but I don't
> > think it's a good way. There are other paths that can call
> > do_invalidatepage , for instance block ioctl to discard and zero_range.
> 
> OK, good point! So my patch is a cleanup that stands on its own and we
> should do it regardless. But I agree we need more to completely fix this.
> I don't quite like the callback you've added just for this special case
> (furthermore it grows size of every buffer_head and there can be lots of
> those). But I agree with the general idea that we shouldn't discard buffers
> that the filesystem is working with.
> 
> In fact I believe that fallocate(2) and zeroout/discard ioctls should
> return EBUSY if they are run against a mounted device because with 99%
> probability something went wrong and you're accidentally discarding the
> wrong device. But maybe I'm wrong. I'll run this idea through other fs
> developers.

I'm going through old patches, and I'm trying to figure out where did
we end up on this issue?   Did we come to a conclusion on this?

One other thing which I noticed when looking at the original patch was
shouldn't lvreduce not be allowed to run on a LV which has a mounted
file system on its block device?

					- Ted

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