From: Matthew Wilcox <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: Remove redundant test from find_get_pages_contig
Date: Tue, 8 Jan 2019 13:36:21 -0800 [thread overview]
Message-ID: <20190108213621.GH6310@bombadil.infradead.org> (raw)
In-Reply-To: <20190108132649.8f25386d966f04b0bccd6d77@linux-foundation.org>
On Tue, Jan 08, 2019 at 01:26:49PM -0800, Andrew Morton wrote:
> On Tue, 8 Jan 2019 12:26:35 -0800 Matthew Wilcox <willy@infradead.org> wrote:
>
> > > Would it be excessively cautious to put a WARN_ON_ONCE() in there for a
> > > while?
> >
> > I think it would ... it'd get in the way of a subsequent patch to store
> > only head pages in the page cache.
>
> OK, shall grab. Perhaps the changelog could gain a few words
> explaining the history, etc.
Yeah, I suck at changelogs. Particularly when I've encountered something
that's distracting me from the thing I was trying to do. How about this:
mm: Remove redundant test from find_get_pages_contig
After we establish a reference on the page, we check the pointer
continues to be in the correct position in i_pages. Checking page->index
afterwards is unnecessary; if it were to change, then the pointer to it
from the page cache would also move. The check used to be done before
grabbing a reference on the page which was racy (see 9cbb4cb21b19f
("mm: find_get_pages_contig fixlet")), but nobody noticed that moving
the check after grabbing the reference was redundant.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
prev parent reply other threads:[~2019-01-08 21:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 20:02 Matthew Wilcox
2019-01-07 22:33 ` Andrew Morton
2019-01-07 22:39 ` Matthew Wilcox
2019-01-07 23:09 ` Andrew Morton
2019-01-08 20:26 ` Matthew Wilcox
2019-01-08 21:26 ` Andrew Morton
2019-01-08 21:36 ` Matthew Wilcox [this message]
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