linux-kernel - [PATCH RESEND v3 05/10] mm/vma: de-duplicate __vma_enter

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Message-ID: <2611b2b6957b7aef587e9ae62712a888159dce60.1769086312.git.lorenzo.stoakes@oracle.com>
Date: Thu, 22 Jan 2026 13:01:57 +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: [PATCH RESEND v3 05/10] mm/vma: de-duplicate __vma_enter_locked() error path

We're doing precisely the same thing that __vma_exit_locked() does, so
de-duplicate this code and keep the refcount primitive in one place.

No functional change intended.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 mm/mmap_lock.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
index 9563bfb051f4..7a0361cff6db 100644
--- a/mm/mmap_lock.c
+++ b/mm/mmap_lock.c
@@ -45,6 +45,14 @@ EXPORT_SYMBOL(__mmap_lock_do_trace_released);

 #ifdef CONFIG_MMU
 #ifdef CONFIG_PER_VMA_LOCK
+
+static inline void __vma_exit_locked(struct vm_area_struct *vma, bool *detached)
+{
+	*detached = refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG,
+					  &vma->vm_refcnt);
+	__vma_lockdep_release_exclusive(vma);
+}
+
 /*
  * __vma_enter_locked() returns 0 immediately if the vma is not
  * attached, otherwise it waits for any current readers to finish and
@@ -77,7 +85,10 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
 		   refcount_read(&vma->vm_refcnt) == tgt_refcnt,
 		   state);
 	if (err) {
-		if (refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG, &vma->vm_refcnt)) {
+		bool detached;
+
+		__vma_exit_locked(vma, &detached);
+		if (detached) {
 			/*
 			 * The wait failed, but the last reader went away
 			 * as well.  Tell the caller the VMA is detached.
@@ -85,7 +96,6 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
 			WARN_ON_ONCE(!detaching);
 			err = 0;
 		}
-		__vma_lockdep_release_exclusive(vma);
 		return err;
 	}
 	__vma_lockdep_stat_mark_acquired(vma);
@@ -93,13 +103,6 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
 	return 1;
 }

-static inline void __vma_exit_locked(struct vm_area_struct *vma, bool *detached)
-{
-	*detached = refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG,
-					  &vma->vm_refcnt);
-	__vma_lockdep_release_exclusive(vma);
-}
-
 int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
 		int state)
 {
--
2.52.0