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SubjectRe: [PATCH v3 3/5] hugetlb: only set HPageMigratable for migratable hstates
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On 2/1/21 3:49 AM, Michal Hocko wrote:
> On Fri 29-01-21 10:46:15, Mike Kravetz wrote:
>> On 1/28/21 2:15 PM, Andrew Morton wrote:
>>> On Thu, 28 Jan 2021 14:00:29 -0800 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>>>
>>>> Michal suggested that comments describing synchronization be added for each
>>>> flag. Since I did 'one patch per flag', that would be an update to each patch.
>>>> Or, I could simply add a patch to update the comment block based on what you
>>>> already have.
>>>>
>>>> Let me know what is best/easiest for you.
>>>
>>> I guess just one patch is best for reviewers. Then I'll split up into
>>> a sprinkle of -fix patches if I'm feeling energetic ;)
>>
>> Here is a patch to update the comments for all those flags. It should
>> apply on top of what is in your tree.
>>
>> From: Mike Kravetz <mike.kravetz@oracle.com>
>> Date: Fri, 29 Jan 2021 10:36:12 -0800
>> Subject: [PATCH] huegtlb: add synchronization information for new hugetlb
>> specific flags
>>
>> Adding comments, no functional change.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> Thanks Mike!

Hi Andrew,

You may have missed this due to the depth of email thread. Can you pick
this up, or would you like me to resend?

Thanks,
--
Mike Kravetz

>
>> ---
>> include/linux/hugetlb.h | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index e5e6ffd55392..cf70795d2209 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -480,14 +480,24 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
>> * HPG_restore_reserve - Set when a hugetlb page consumes a reservation at
>> * allocation time. Cleared when page is fully instantiated. Free
>> * routine checks flag to restore a reservation on error paths.
>> + * Synchronization: Examined or modified by code that knows it has
>> + * the only reference to page. i.e. After allocation but before use
>> + * or when the page is being freed.
>> * HPG_migratable - Set after a newly allocated page is added to the page
>> * cache and/or page tables. Indicates the page is a candidate for
>> * migration.
>> + * Synchronization: Initially set after new page allocation with no
>> + * locking. When examined and modified during migration processing
>> + * (isolate, migrate, putback) the hugetlb_lock is held.
>> * HPG_temporary - - Set on a page that is temporarily allocated from the buddy
>> * allocator. Typically used for migration target pages when no pages
>> * are available in the pool. The hugetlb free page path will
>> * immediately free pages with this flag set to the buddy allocator.
>> + * Synchronization: Can be set after huge page allocation from buddy when
>> + * code knows it has only reference. All other examinations and
>> + * modifications require hugetlb_lock.
>> * HPG_freed - Set when page is on the free lists.
>> + * Synchronization: hugetlb_lock held for examination and modification.
>> */
>> enum hugetlb_page_flags {
>> HPG_restore_reserve = 0,
>> --
>> 2.29.2
>>
>

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