linux-kernel - Re: [PATCH v4 08/10] mm/vma: improve and document __is_vma_write

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Message-ID: <3fa89c13-232d-4eee-86cc-96caa75c2c67@lucifer.local>
Date: Mon, 26 Jan 2026 16:30:13 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...nel.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Shakeel Butt <shakeel.butt@...ux.dev>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-rt-devel@...ts.linux.dev, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Clark Williams <clrkwllms@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v4 08/10] mm/vma: improve and document
 __is_vma_write_locked()

Hi Andrew,

Could you apply the attached fix-patch to address Vlasta's nits? Thanks! :)

Cheers, Lorenzo

----8<----
>From d6f05f5f0c2ada298e90deaaf3eefdcabc4d344a Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Date: Mon, 26 Jan 2026 16:23:16 +0000
Subject: [PATCH] fix

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 include/linux/mmap_lock.h | 9 +++------
 mm/mmap_lock.c            | 6 +++---
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 23bde4bd5a85..1746a172a81c 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -272,8 +272,6 @@ static inline unsigned int __vma_raw_mm_seqnum(struct vm_area_struct *vma)
  * write lock is held.
  *
  * Returns true if write-locked, otherwise false.
- *
- * Note that mm_lock_seq is updated only if the VMA is NOT write-locked.
  */
 static inline bool __is_vma_write_locked(struct vm_area_struct *vma)
 {
@@ -284,8 +282,7 @@ static inline bool __is_vma_write_locked(struct vm_area_struct *vma)
 	return vma->vm_lock_seq == __vma_raw_mm_seqnum(vma);
 }

-int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
-		int state);
+int __vma_start_write(struct vm_area_struct *vma, int state);

 /*
  * Begin writing to a VMA.
@@ -297,7 +294,7 @@ static inline void vma_start_write(struct vm_area_struct *vma)
 	if (__is_vma_write_locked(vma))
 		return;

-	__vma_start_write(vma, __vma_raw_mm_seqnum(vma), TASK_UNINTERRUPTIBLE);
+	__vma_start_write(vma, TASK_UNINTERRUPTIBLE);
 }

 /**
@@ -319,7 +316,7 @@ int vma_start_write_killable(struct vm_area_struct *vma)
 	if (__is_vma_write_locked(vma))
 		return 0;

-	return __vma_start_write(vma, __vma_raw_mm_seqnum(vma), TASK_KILLABLE);
+	return __vma_start_write(vma, TASK_KILLABLE);
 }

 static inline void vma_assert_write_locked(struct vm_area_struct *vma)
diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
index b523a3fe110c..a9ad6a573270 100644
--- a/mm/mmap_lock.c
+++ b/mm/mmap_lock.c
@@ -136,14 +136,14 @@ static int __vma_start_exclude_readers(struct vma_exclude_readers_state *ves)
 	return 0;
 }

-int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
-		int state)
+int __vma_start_write(struct vm_area_struct *vma, int state)
 {
-	int err;
+	const unsigned int mm_lock_seq = __vma_raw_mm_seqnum(vma);
 	struct vma_exclude_readers_state ves = {
 		.vma = vma,
 		.state = state,
 	};
+	int err;

 	err = __vma_start_exclude_readers(&ves);
 	if (err) {
--
2.52.0