+ mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch added to mm-unstable branch

+ mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/khugepaged: cleanup memcg uncharge for failure path
has been added to the -mm mm-unstable branch.  Its filename is
     mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Peter Xu <peterx@redhat.com>
Subject: mm/khugepaged: cleanup memcg uncharge for failure path
Date: Fri, 3 Mar 2023 10:12:18 -0500

Explicit memcg uncharging is not needed when the memcg accounting has the
same lifespan of the page/folio.  That becomes the case for khugepaged
after Yang & Zach's recent rework so the hpage will be allocated for each
collapse rather than being cached.

Cleanup the explicit memcg uncharge in khugepaged failure path and leave
that for put_page().

Link: https://lkml.kernel.org/r/20230303151218.311015-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Suggested-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: David Stevens <stevensd@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/khugepaged.c~mm-khugepaged-cleanup-memcg-uncharge-for-failure-path
+++ a/mm/khugepaged.c
@@ -1136,10 +1136,8 @@ static int collapse_huge_page(struct mm_
 out_up_write:
 	mmap_write_unlock(mm);
 out_nolock:
-	if (hpage) {
-		mem_cgroup_uncharge(page_folio(hpage));
+	if (hpage)
 		put_page(hpage);
-	}
 	trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
 	return result;
 }
@@ -2145,10 +2143,8 @@ xa_unlocked:
 		unlock_page(hpage);
 out:
 	VM_BUG_ON(!list_empty(&pagelist));
-	if (hpage) {
-		mem_cgroup_uncharge(page_folio(hpage));
+	if (hpage)
 		put_page(hpage);
-	}
 
 	trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
 	return result;
_

Patches currently in -mm which might be from peterx@redhat.com are

mm-khugepaged-alloc_charge_hpage-take-care-of-mem-charge-errors.patch
mm-khugepaged-cleanup-memcg-uncharge-for-failure-path.patch