mm/rmap: separate out fork-only logic on anon_vma_clone()

Specify which operation is being performed to anon_vma_clone(), which
allows us to do checks specific to each operation type, as well as to
separate out and make clear that the anon_vma reuse logic is absolutely
specific to fork only.

This opens the door to further refactorings and refinements later as we
have more information to work with.

Link: https://lkml.kernel.org/r/cf7da7a2d973cdc72a1b80dd9a73260519e8fa9f.1768746221.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chris Li <chriscli@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/mm/internal.h b/mm/internal.h
index aac4ec53fe15..5585059f0209 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -244,7 +244,16 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
 
 struct anon_vma *folio_get_anon_vma(const struct folio *folio);
 
-int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src);
+/* Operations which modify VMAs. */
+enum vma_operation {
+	VMA_OP_SPLIT,
+	VMA_OP_MERGE_UNFAULTED,
+	VMA_OP_REMAP,
+	VMA_OP_FORK,
+};
+
+int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src,
+	enum vma_operation operation);
 int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma);
 int  __anon_vma_prepare(struct vm_area_struct *vma);
 void unlink_anon_vmas(struct vm_area_struct *vma);