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Date:   Wed, 30 Mar 2022 08:54:09 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     Christoph Hellwig <hch@infradead.org>, CGEL <cgel.zte@gmail.com>,
        axboe@kernel.dk, viro@zeniv.linux.org.uk,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org,
        Yang Yang <yang.yang29@zte.com.cn>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>
Subject: Re: [PATCH] block/psi: make PSI annotations of submit_bio only work
 for file pages
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On Wed, Mar 30, 2022 at 11:45:56AM -0400, Johannes Weiner wrote:
> > FYI, I started redoing that version and I think with all the cleanups
> > to filemap.c and the readahead code this can be done fairly nicely now:
> > 
> > http://git.infradead.org/users/hch/block.git/commitdiff/666abb29c6db870d3941acc5ac19e83fbc72cfd4
> 
> Yes, it's definitely much nicer now with the MM instantiating the
> pages for ->readpage(s).
> 
> But AFAICS this breaks compressed btrfs (and erofs?) because those
> still do additional add_to_page_cache_lru() and bio submissions.

In btrfs, add_ra_bio_pages only passed freshly allocated pages to
add_to_page_cache_lru.  These can't really have PageWorkingSet set,
can they?  In erofs they can also come from a local page pool, but
I think otherwise the same applies.