[PATCH 4/8] mm/rmap: remove anon_vma_merge() function

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

This function is confusing, we already have the concept of anon_vma merge
to adjacent VMA's anon_vma's to increase probability of anon_vma
compatibility and therefore VMA merge (see is_mergeable_anon_vma() etc.),
as well as anon_vma reuse, along side the usual VMA merge logic.

We can remove the anon_vma check as it is redundant - a merge would not
have been permitted with removal if the anon_vma's were not the same (and
in the case of an unfaulted/faulted merge, we would have already set the
unfaulted VMA's anon_vma to vp->remove->anon_vma in dup_anon_vma()).

Avoid overloading this term when we're very simply unlinking anon_vma state
from a removed VMA upon merge.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 include/linux/rmap.h             | 7 -------
 mm/vma.c                         | 2 +-
 tools/testing/vma/vma_internal.h | 5 -----
 3 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index daa92a58585d..832bfc0ccfc6 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -165,13 +165,6 @@ static inline int anon_vma_prepare(struct vm_area_struct *vma)
 	return __anon_vma_prepare(vma);
 }

-static inline void anon_vma_merge(struct vm_area_struct *vma,
-				  struct vm_area_struct *next)
-{
-	VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
-	unlink_anon_vmas(next);
-}
-
 struct anon_vma *folio_get_anon_vma(const struct folio *folio);

 #ifdef CONFIG_MM_ID
diff --git a/mm/vma.c b/mm/vma.c
index fc90befd162f..feb4bbd3b259 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -376,7 +376,7 @@ static void vma_complete(struct vma_prepare *vp, struct vma_iterator *vmi,
 			fput(vp->file);
 		}
 		if (vp->remove->anon_vma)
-			anon_vma_merge(vp->vma, vp->remove);
+			unlink_anon_vmas(vp->remove);
 		mm->map_count--;
 		mpol_put(vma_policy(vp->remove));
 		if (!vp->remove2)
diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index 9f0a9f5ed0fe..93e5792306d9 100644
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -1265,11 +1265,6 @@ static inline void i_mmap_unlock_write(struct address_space *mapping)
 {
 }

-static inline void anon_vma_merge(struct vm_area_struct *vma,
-				  struct vm_area_struct *next)
-{
-}
-
 static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
 					 unsigned long start,
 					 unsigned long end,
--
2.52.0