From: Matthew Wilcox <willy@infradead.org>
To: Chao Yu <chao@kernel.org>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>,
linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org
Subject: Re: [f2fs-dev] [PATCH] f2fs: initialize page->private when using for our internal use
Date: Mon, 5 Jul 2021 12:47:48 +0100 [thread overview]
Message-ID: <YOLxZAnaKSwBIlK9@casper.infradead.org> (raw)
In-Reply-To: <e2fdf628-f25c-7495-cfd1-952899f7ff9a@kernel.org>
On Mon, Jul 05, 2021 at 07:33:35PM +0800, Chao Yu wrote:
> On 2021/7/5 16:56, Jaegeuk Kim wrote:
> > On 07/05, Chao Yu wrote:
> > > On 2021/7/5 13:22, Jaegeuk Kim wrote:
> > > > We need to guarantee it's initially zero. Otherwise, it'll hurt entire flag
> > > > operations.
> > >
> > > Oops, I didn't get the point, shouldn't .private be zero after page was
> > > just allocated by filesystem? What's the case we will encounter stall
> > > private data left in page?
> >
> > I'm seeing f2fs_migrate_page() has the newpage with some value without Private
> > flag. That causes a kernel panic later due to wrong private flag used in f2fs.
>
> I'm not familiar with that part of codes, so Cc mm mailing list for help.
>
> My question is newpage in .migrate_page() may contain non-zero value in .private
> field but w/o setting PagePrivate flag, is it a normal case?
I think freshly allocated pages have a page->private of 0. ie this
code in mm/page_alloc.c:
page = rmqueue(ac->preferred_zoneref->zone, zone, order,
gfp_mask, alloc_flags, ac->migratetype);
if (page) {
prep_new_page(page, order, gfp_mask, alloc_flags);
where prep_new_page() calls post_alloc_hook() which contains:
set_page_private(page, 0);
Now, I do see in __buffer_migrate_page() (mm/migrate.c):
attach_page_private(newpage, detach_page_private(page));
but as far as I can tell, f2fs doesn't call any of the
buffer_migrate_page() paths. So I'm not sure why you're seeing
a non-zero page->private.
next prev parent reply other threads:[~2021-07-05 11:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210705052216.831989-1-jaegeuk@kernel.org>
[not found] ` <c32642d6-6de2-eb2d-5771-c7cefa62fab5@kernel.org>
[not found] ` <YOLJW0IgCagMk2tF@google.com>
2021-07-05 11:33 ` [f2fs-dev] [PATCH] f2fs: initialize page->private when using for our internal use Chao Yu
2021-07-05 11:47 ` Matthew Wilcox [this message]
2021-07-05 16:09 ` Chao Yu
2021-07-05 18:06 ` Jaegeuk Kim
2021-07-06 0:16 ` Chao Yu
2021-07-05 18:04 ` Jaegeuk Kim
2021-07-05 18:45 ` Matthew Wilcox
2021-07-06 9:12 ` Mel Gorman
2021-07-07 0:48 ` Chao Yu
2021-07-07 9:57 ` Mel Gorman
2021-07-10 8:11 ` Chao Yu
2021-07-12 6:53 ` Michal Hocko
2021-07-13 0:46 ` Chao Yu
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