On 1/28/21 2:15 PM, Andrew Morton wrote:
> On Thu, 28 Jan 2021 14:00:29 -0800 Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx>
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@xxxxxxxxxx>
---
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
