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Date:   Sat, 19 Dec 2020 15:33:12 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Jeff Layton <jlayton@kernel.org>
Cc:     Amir Goldstein <amir73il@gmail.com>,
        Sargun Dhillon <sargun@sargun.me>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Vivek Goyal <vgoyal@redhat.com>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        NeilBrown <neilb@suse.com>, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH v3] errseq: split the ERRSEQ_SEEN flag into two new flags
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On Sat, Dec 19, 2020 at 07:53:12AM -0500, Jeff Layton wrote:
> On Sat, 2020-12-19 at 06:13 +0000, Matthew Wilcox wrote:
> > On Thu, Dec 17, 2020 at 10:00:37AM -0500, Jeff Layton wrote:
> > > Overlayfs's volatile mounts want to be able to sample an error for their
> > > own purposes, without preventing a later opener from potentially seeing
> > > the error.
> > 
> > umm ... can't they just copy the errseq_t they're interested in, followed
> > by calling errseq_check() later?
> > 
> 
> They don't want the sampling for the volatile mount to prevent later
> openers from seeing an error that hasn't yet been reported.

That's why they should use errseq_check(), not errseq_check_and_advance()
...