FAILED: patch "[PATCH] mm/memcg: set memcg when splitting page" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e1baddf8475b06cc56f4bafecf9a32a124343d9f Mon Sep 17 00:00:00 2001
From: Zhou Guanghui <[email protected]>
Date: Fri, 12 Mar 2021 21:08:33 -0800
Subject: [PATCH] mm/memcg: set memcg when splitting page

As described in the split_page() comment, for the non-compound high order page, the sub-pages must be freed individually. If the memcg of the first page is valid, the tail pages cannot be uncharged when be freed.

For example, when alloc_pages_exact is used to allocate 1MB continuous physical memory, 2MB is charged(kmemcg is enabled and __GFP_ACCOUNT is set). When make_alloc_exact free the unused 1MB and free_pages_exact free the applied 1MB, actually, only 4KB(one page) is uncharged.

Therefore, the memcg of the tail page needs to be set when splitting a page.

Michel:

There are at least two explicit users of __GFP_ACCOUNT with alloc_exact_pages added recently. See 7efe8ef274024 ("KVM: arm64:
Allocate stage-2 pgd pages with GFP_KERNEL_ACCOUNT") and c419621873713 ("KVM: s390: Add memcg accounting to KVM allocations"), so this is not just a theoretical issue.

index 3cd1c0ce4d06..cfc72873961d 100644
@@ -3314,6 +3314,7 @@ void split_page(struct page *page, unsigned int order)
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
 	split_page_owner(page, 1 << order);
+	split_page_memcg(page, 1 << order);
 }
 EXPORT_SYMBOL_GPL(split_page);
 

That's odd, I think what I'm sending here is the same as what you had originally: maybe it was a build issue - if this one goes before the other then its build would break, because it assumes the rename.

Hugh

------------------ original commit in Linus's tree ------------------

From e1baddf8475b06cc56f4bafecf9a32a124343d9f Mon Sep 17 00:00:00 2001
From: Zhou Guanghui <[email protected]>
Date: Fri, 12 Mar 2021 21:08:33 -0800
Subject: [PATCH 2/2] mm/memcg: set memcg when splitting page

As described in the split_page() comment, for the non-compound high order page, the sub-pages must be freed individually. If the memcg of the first page is valid, the tail pages cannot be uncharged when be freed.

For example, when alloc_pages_exact is used to allocate 1MB continuous physical memory, 2MB is charged(kmemcg is enabled and __GFP_ACCOUNT is set). When make_alloc_exact free the unused 1MB and free_pages_exact free the applied 1MB, actually, only 4KB(one page) is uncharged.

Therefore, the memcg of the tail page needs to be set when splitting a page.

Michel:

There are at least two explicit users of __GFP_ACCOUNT with alloc_exact_pages added recently. See 7efe8ef274024 ("KVM: arm64:
Allocate stage-2 pgd pages with GFP_KERNEL_ACCOUNT") and c419621873713 ("KVM: s390: Add memcg accounting to KVM allocations"), so this is not just a theoretical issue.

---
 mm/page_alloc.c | 1 +
 1 file changed, 1 insertion(+)

index 690f79c781cf..7ffa706e5c30 100644
@@ -3272,6 +3272,7 @@ void split_page(struct page *page, unsigned int order)
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
 	split_page_owner(page, 1 << order);
+	split_page_memcg(page, 1 << order);
 }
 EXPORT_SYMBOL_GPL(split_page);
 

2.31.0.291.g576ba9dcdaf-goog