From: David Howells <dhowells@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: dhowells@redhat.com, dwysocha@redhat.com,
Rohith Surabattula <rohiths.msft@gmail.com>,
Steve French <sfrench@samba.org>,
Shyam Prasad N <nspmangalore@gmail.com>,
Dominique Martinet <asmadeus@codewreck.org>,
Ilya Dryomov <idryomov@gmail.com>,
linux-cachefs@redhat.com, linux-cifs@vger.kernel.org,
linux-afs@lists.infradead.org,
v9fs-developer@lists.sourceforge.net, ceph-devel@vger.kernel.org,
linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2] mm, netfs, fscache: Stop read optimisation when folio removed from pagecache
Date: Tue, 15 Nov 2022 09:40:49 +0000 [thread overview]
Message-ID: <1493972.1668505249@warthog.procyon.org.uk> (raw)
In-Reply-To: <Y3MQ4l1AJOgniprT@casper.infradead.org>
Matthew Wilcox <willy@infradead.org> wrote:
> On Mon, Nov 14, 2022 at 04:02:20PM +0000, David Howells wrote:
> > +++ b/mm/filemap.c
> > @@ -3941,6 +3941,10 @@ bool filemap_release_folio(struct folio *folio, gfp_t gfp)
> > struct address_space * const mapping = folio->mapping;
> >
> > BUG_ON(!folio_test_locked(folio));
> > + if ((!mapping || !mapping_release_always(mapping))
> > + && !folio_test_private(folio) &&
> > + !folio_test_private_2(folio))
> > + return true;
>
> Why do you need to test 'mapping' here?
Why does the function do:
if (mapping && mapping->a_ops->release_folio)
later then? There are callers of the function, such as shrink_folio_list(),
that seem to think that folio->mapping might be NULL.
> Also this is the most inconsistent style ...
Yeah, I accidentally pushed the '&&' onto the next line.
> > @@ -276,7 +275,7 @@ static long mapping_evict_folio(struct address_space *mapping,
> > if (folio_ref_count(folio) >
> > folio_nr_pages(folio) + folio_has_private(folio) + 1)
>
> I think this line is incorrect, right? You don't increment the folio
> refcount just because the folio has private2 set, do you?
Errr, yes:
static inline void folio_start_fscache(struct folio *folio)
{
VM_BUG_ON_FOLIO(folio_test_private_2(folio), folio);
folio_get(folio);
folio_set_private_2(folio);
}
Someone insisted - might even have been you;-)
I'm working on getting rid of the use of PG_private_2 from the network
filesystems, but it's still in progress. Kind of blocked on the iov_iter
stuff.
> > return 0;
> > - if (folio_has_private(folio) && !filemap_release_folio(folio, 0))
> > + if (!filemap_release_folio(folio, 0))
> > return 0;
> >
> > return remove_mapping(mapping, folio);
>
> Can we get rid of folio_has_private()
That would be nice, but there are still places that check it, and until we get
rid of the use of PG_private_2, we can't reduce it to just a check on
PG_private. Truncate, for example, checks it to see if it should can
->invalidate_folio().
It's only used in mm/, so it could be moved into mm/internal.h.
> / page_has_private() now?
That's used in some a number of places outside of mm/. The arch/s390/ usage
is just to calculate the expected refcount. I wonder if calculation of the
expected refcount could be potted into a function as it's performed in a
number of places - though the expectation isn't always the same.
Ext3 and fuse both use it - but those probably need to check PG_private_2 and
could use a "folio_test_private()" function when fully foliated.
David
prev parent reply other threads:[~2022-11-15 9:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-14 16:02 [RFC PATCH v2] mm, netfs, fscache: Stop read optimisation when folio removed from pagecache David Howells
2022-11-15 0:22 ` Dominique Martinet
2022-11-15 0:41 ` David Howells
2022-11-15 2:34 ` Dominique Martinet
2022-11-15 4:09 ` Matthew Wilcox
2022-11-15 9:40 ` David Howells [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1493972.1668505249@warthog.procyon.org.uk \
--to=dhowells@redhat.com \
--cc=asmadeus@codewreck.org \
--cc=ceph-devel@vger.kernel.org \
--cc=dwysocha@redhat.com \
--cc=idryomov@gmail.com \
--cc=linux-afs@lists.infradead.org \
--cc=linux-cachefs@redhat.com \
--cc=linux-cifs@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-nfs@vger.kernel.org \
--cc=nspmangalore@gmail.com \
--cc=rohiths.msft@gmail.com \
--cc=sfrench@samba.org \
--cc=v9fs-developer@lists.sourceforge.net \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).