From: Chao Yu <chao@kernel.org>
To: Matthew Wilcox <willy@infradead.org>, Jaegeuk Kim <jaegeuk@kernel.org>
Cc: 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: Tue, 6 Jul 2021 00:09:18 +0800 [thread overview]
Message-ID: <5ab8d01a-8fac-60b2-9c2c-a32c5a81b394@kernel.org> (raw)
In-Reply-To: <YOLxZAnaKSwBIlK9@casper.infradead.org>
On 2021/7/5 19:47, Matthew Wilcox wrote:
> 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.
Well, that's strange.
Jaegeuk, let's add a BUGON in f2fs to track the call path where newpage
has non-zero private value? if this issue is reproducible.
Thanks,
>
next prev parent reply other threads:[~2021-07-05 16:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 5:22 [PATCH] f2fs: initialize page->private when using for our internal use Jaegeuk Kim
2021-07-05 6:32 ` [f2fs-dev] " Chao Yu
2021-07-05 8:56 ` Jaegeuk Kim
2021-07-05 11:33 ` Chao Yu
2021-07-05 11:47 ` Matthew Wilcox
2021-07-05 16:09 ` Chao Yu [this message]
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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