linux-kernel - [PATCH] mm: move dummy_vm

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Message-Id: <20230805014055.1280320-1-mjguzik@gmail.com>
Date:   Sat,  5 Aug 2023 03:40:55 +0200
From:   Mateusz Guzik <mjguzik@...il.com>
To:     surenb@...gle.com
Cc:     linux-mm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH] mm: move dummy_vm_ops out of a header

Otherwise the kernel ends up with multiple copies:
$ nm vmlinux | grep dummy_vm_ops
ffffffff81e4ea00 d dummy_vm_ops.2
ffffffff81e11760 d dummy_vm_ops.254
ffffffff81e406e0 d dummy_vm_ops.4
ffffffff81e3c780 d dummy_vm_ops.7

[if someone has better ideas where to put it, please move it]

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---
 include/linux/mm.h | 6 +++---
 mm/init-mm.c       | 2 ++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 406ab9ea818f..14898e76bbf1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -756,17 +756,17 @@ static inline void vma_mark_detached(struct vm_area_struct *vma,
 
 #endif /* CONFIG_PER_VMA_LOCK */
 
+extern const struct vm_operations_struct vma_dummy_vm_ops;
+
 /*
  * WARNING: vma_init does not initialize vma->vm_lock.
  * Use vm_area_alloc()/vm_area_free() if vma needs locking.
  */
 static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 {
-	static const struct vm_operations_struct dummy_vm_ops = {};
-
 	memset(vma, 0, sizeof(*vma));
 	vma->vm_mm = mm;
-	vma->vm_ops = &dummy_vm_ops;
+	vma->vm_ops = &vma_dummy_vm_ops;
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
 	vma_mark_detached(vma, false);
 	vma_numab_state_init(vma);
diff --git a/mm/init-mm.c b/mm/init-mm.c
index efa97b57acfd..cfd367822cdd 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -17,6 +17,8 @@
 #define INIT_MM_CONTEXT(name)
 #endif
 
+const struct vm_operations_struct vma_dummy_vm_ops;
+
 /*
  * For dynamically allocated mm_structs, there is a dynamically sized cpumask
  * at the end of the structure, the size of which depends on the maximum CPU
-- 
2.39.2