From: Matthew Wilcox <willy@infradead.org>
To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Subject: [f2fs-dev] [RFC] Reclaiming PG_private
Date: Thu, 22 Apr 2021 16:47:05 +0100 [thread overview]
Message-ID: <20210422154705.GO3596236@casper.infradead.org> (raw)
We're perenially short of page flags, and I don't really see the need
for PG_private to exist. We have 32/64 bits available in page->private,
and we don't seem to need the extra bit.
Most users store a pointer in page->private, and so PagePrivate() being
implemented as page->private != 0 is appropriate.
Some users simply SetPagePrivate() and don't touch page->private.
Those users could instead set page->private to 1.
Do we have any users which want to SetPagePrivate() and want to put a
meaningful zero value in page->private?
AFS stores a pair of integers in page->private, but the second integer
must be greater than the first one, so they can't both be zero. btrfs
stores a real or fake pointer. buffer_head filesystems generally store
a buffer_head pointer. fscrypt stores a pointer. erofs stores a real or
fake pointer. f2fs does set PagePrivate and also set the pointer to NULL,
but it's not clear whether that's intentional. iomap stores a pointer.
jfs stores a pointer. nfs stores a pointer. ntfs stores a pointer.
orangefs stores a pointer.
So ... what's going on with f2fs? Does it need to distinguish between
a page which has f2fs_set_page_private(page, 0) called on it, and a page
which has had f2fs_clear_page_private() called on it?
_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
reply other threads:[~2021-04-22 15:48 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
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=20210422154705.GO3596236@casper.infradead.org \
--to=willy@infradead.org \
--cc=linux-f2fs-devel@lists.sourceforge.net \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-mm@kvack.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).