From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
"Vishal Moola (Oracle)" <vishal.moola@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steve French <smfrench@gmail.com>,
Steve French <stfrench@microsoft.com>,
Shyam Prasad N <nspmangalore@gmail.com>,
Rohith Surabattula <rohiths.msft@gmail.com>,
Tom Talpey <tom@talpey.com>, Paulo Alcantara <pc@cjr.nz>,
Jeff Layton <jlayton@kernel.org>,
linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-next@vger.kernel.org
Subject: Re: linux-next: manual merge of the mm-stable tree with the cifs tree
Date: Tue, 21 Feb 2023 15:26:36 +0000 [thread overview]
Message-ID: <Y/TirOtSETOvh2py@casper.infradead.org> (raw)
In-Reply-To: <2887475.1676991926@warthog.procyon.org.uk>
On Tue, Feb 21, 2023 at 03:05:26PM +0000, David Howells wrote:
> Matthew Wilcox <willy@infradead.org> wrote:
>
> > > + start = folio_pos(folio); /* May regress with THPs */
> >
> > What does this comment mean?
>
> "start" may end up going backwards if it's pointing to the middle of a folio.
So that's "regress" in the sense of "May point earlier in the file",
rather than "May cause a bug" (which was how I read it)?
> > > + /* At this point we hold neither the i_pages lock nor the
> > > + * page lock: the page may be truncated or invalidated
> > > + * (changing page->mapping to NULL), or even swizzled
> > > + * back from swapper_space to tmpfs file mapping
> >
> > Where does this comment come from? This is cifs, not tmpfs. You'll
> > never be asked to writeback a page from the swap cache. Dirty pages
> > can be truncated, so the first half of the comment is still accurate.
> > I'd rather it moved down to below the folio lock, and was rephrased
> > so it described why we're checking everything again.
>
> I picked it up into afs from somewhere - nfs maybe? The same comment is in
> fs/btrfs/extent_io.c. grep for 'swizzled' in fs/. You modified the comment
> in b93b016313b3ba8003c3b8bb71f569af91f19fc7 in 2018, so it's been around a
> while.
I was just removing references to ->tree_lock ;-)
next prev parent reply other threads:[~2023-02-21 15:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-20 4:29 linux-next: manual merge of the mm-stable tree with the cifs tree Stephen Rothwell
2023-02-20 13:58 ` Matthew Wilcox
2023-02-20 8:01 ` Stephen Rothwell
2023-02-20 20:58 ` Matthew Wilcox
2023-02-21 6:44 ` Stephen Rothwell
2023-02-21 7:19 ` David Howells
2023-02-21 7:42 ` Stephen Rothwell
2023-02-21 14:39 ` David Howells
2023-02-21 14:55 ` Matthew Wilcox
2023-02-21 15:05 ` David Howells
2023-02-21 15:26 ` Matthew Wilcox [this message]
2023-02-21 15:20 ` David Howells
2023-02-21 15:30 ` Obsolete comment on page swizzling (written by Hugh)? David Howells
[not found] ` <2890066.1676993700@warthog.procyon.org.uk>
2023-02-21 22:41 ` Hugh Dickins
2023-02-22 2:49 ` linux-next: manual merge of the mm-stable tree with the cifs tree Stephen Rothwell
2023-02-22 8:27 ` David Howells
2023-02-22 12:13 ` Stephen Rothwell
2023-02-20 21:00 ` Steve French
2023-02-21 6:50 ` Stephen Rothwell
2023-02-20 14:29 ` David Howells
2023-02-20 15:12 ` Matthew Wilcox
2023-02-20 8:05 ` Stephen Rothwell
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