linux-kernel - [PATCH] mm/thp: fix "mm: thp: kill __transhuge_page

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Message-ID: <20230812210053.2325091-1-zokeefe@google.com>
Date:   Sat, 12 Aug 2023 14:00:53 -0700
From:   "Zach O'Keefe" <zokeefe@...gle.com>
To:     linux-mm@...ck.org, Yang Shi <shy828301@...il.com>
Cc:     linux-kernel@...r.kernel.org, "Zach O'Keefe" <zokeefe@...gle.com>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>
Subject: [PATCH] mm/thp: fix "mm: thp: kill __transhuge_page_enabled()"

The 6.0 commits:

commit 9fec51689ff6 ("mm: thp: kill transparent_hugepage_active()")
commit 7da4e2cb8b1f ("mm: thp: kill __transhuge_page_enabled()")

merged "can we have THPs in this VMA?" logic that was previously done
separately by fault-path, khugepaged, and smaps "THPeligible".

During the process, the check on VM_NO_KHUGEPAGED from the khugepaged
path was accidentally added to fault and smaps paths.  Certainly the
previous behavior for fault should be restored, and since smaps should
report the union of THP eligibility for fault and khugepaged, also opt
smaps out of this constraint.

Fixes: 7da4e2cb8b1f ("mm: thp: kill __transhuge_page_enabled()")
Reported-by: Saurabh Singh Sengar <ssengar@...rosoft.com>
Signed-off-by: Zach O'Keefe <zokeefe@...gle.com>
Cc: Yang Shi <shy828301@...il.com>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index eb3678360b97..e098c26d5e2e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -96,11 +96,11 @@ bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
 		return in_pf;
 
 	/*
-	 * Special VMA and hugetlb VMA.
+	 * khugepaged check for special VMA and hugetlb VMA.
 	 * Must be checked after dax since some dax mappings may have
 	 * VM_MIXEDMAP set.
 	 */
-	if (vm_flags & VM_NO_KHUGEPAGED)
+	if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED))
 		return false;
 
 	/*
-- 
2.41.0.694.ge786442a9b-goog