[PATCH v10 09/18] mm: uninline the main body of vma_start_write()

[Suren Baghdasaryan <surenb@google.com>]

vma_start_write() is used in many places and will grow in size very soon.
It is not used in performance critical paths and uninlining it should
limit the future code size growth.
No functional changes.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
Changes since v9 [1]:
- Add Reviewed-by, per Lorenzo Stoakes

[1] https://lore.kernel.org/all/20250111042604.3230628-10-surenb@google.com/

 include/linux/mm.h | 12 +++---------
 mm/memory.c        | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7fa7c39162fd..557d66e187ff 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -787,6 +787,8 @@ static bool __is_vma_write_locked(struct vm_area_struct *vma, unsigned int *mm_l
 	return (vma->vm_lock_seq == *mm_lock_seq);
 }
 
+void __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq);
+
 /*
  * Begin writing to a VMA.
  * Exclude concurrent readers under the per-VMA lock until the currently
@@ -799,15 +801,7 @@ static inline void vma_start_write(struct vm_area_struct *vma)
 	if (__is_vma_write_locked(vma, &mm_lock_seq))
 		return;
 
-	down_write(&vma->vm_lock.lock);
-	/*
-	 * We should use WRITE_ONCE() here because we can have concurrent reads
-	 * from the early lockless pessimistic check in vma_start_read().
-	 * We don't really care about the correctness of that early check, but
-	 * we should use WRITE_ONCE() for cleanliness and to keep KCSAN happy.
-	 */
-	WRITE_ONCE(vma->vm_lock_seq, mm_lock_seq);
-	up_write(&vma->vm_lock.lock);
+	__vma_start_write(vma, mm_lock_seq);
 }
 
 static inline void vma_assert_write_locked(struct vm_area_struct *vma)
diff --git a/mm/memory.c b/mm/memory.c
index e600a5ff3c7a..3d9c5141193f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6393,6 +6393,20 @@ struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
 #endif
 
 #ifdef CONFIG_PER_VMA_LOCK
+void __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq)
+{
+	down_write(&vma->vm_lock.lock);
+	/*
+	 * We should use WRITE_ONCE() here because we can have concurrent reads
+	 * from the early lockless pessimistic check in vma_start_read().
+	 * We don't really care about the correctness of that early check, but
+	 * we should use WRITE_ONCE() for cleanliness and to keep KCSAN happy.
+	 */
+	WRITE_ONCE(vma->vm_lock_seq, mm_lock_seq);
+	up_write(&vma->vm_lock.lock);
+}
+EXPORT_SYMBOL_GPL(__vma_start_write);
+
 /*
  * Lookup and lock a VMA under RCU protection. Returned VMA is guaranteed to be
  * stable and not isolated. If the VMA is not found or is being modified the
-- 
2.48.1.601.g30ceb7b040-goog