From: Nico Pache <npache@redhat.com>
Date: Fri, 5 Jun 2026 16:14:19 +0000 (-0600)
Subject: mm/khugepaged: avoid unnecessary mTHP collapse attempts
X-Git-Tag: v7.2-rc1~59^2~101
X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=5fea7eb1a33154a94ae7be3cd062fec8adfe2fad;p=thirdparty%2Flinux.git

mm/khugepaged: avoid unnecessary mTHP collapse attempts

There are cases where, if an attempted collapse fails, all subsequent
orders are guaranteed to also fail.  Avoid these collapse attempts by
bailing out early.

Link: https://lore.kernel.org/20260605161422.213817-13-npache@redhat.com
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Usama Arif <usama.arif@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Takashi Iwai (SUSE) <tiwai@suse.de>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index e57289f4d3c66..5a2adbdbd0557 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1504,6 +1504,7 @@ static enum scan_result mthp_collapse(struct mm_struct *mm,
 			collapse_address = address + offset * PAGE_SIZE;
 			ret = collapse_huge_page(mm, collapse_address, referenced,
 						 unmapped, cc, order);
+
 			switch (ret) {
 			/* Cases where we continue to next collapse candidate */
 			case SCAN_SUCCEED:
@@ -1514,6 +1515,18 @@ static enum scan_result mthp_collapse(struct mm_struct *mm,
 			/* Cases where lower orders might still succeed */
 			case SCAN_ALLOC_HUGE_PAGE_FAIL:
 				alloc_failed = true;
+				fallthrough;
+			case SCAN_LACK_REFERENCED_PAGE:
+			case SCAN_EXCEED_NONE_PTE:
+			case SCAN_EXCEED_SWAP_PTE:
+			case SCAN_EXCEED_SHARED_PTE:
+			case SCAN_PAGE_LOCK:
+			case SCAN_PAGE_COUNT:
+			case SCAN_PAGE_NULL:
+			case SCAN_DEL_PAGE_LRU:
+			case SCAN_PTE_NON_PRESENT:
+			case SCAN_PTE_UFFD_WP:
+			case SCAN_PAGE_LAZYFREE:
 				last_result = ret;
 				goto next_order;
 			/* Cases where no further collapse is possible */