lkml.org 
[lkml]   [2021]   [Jul]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [f2fs-dev] [PATCH] f2fs: initialize page->private when using for our internal use
From
Date
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,

>

\
 
 \ /
  Last update: 2021-07-05 18:09    [W:0.091 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site