mm: mark vma as detached until it's added into vma tree

Current implementation does not set detached flag when a VMA is first
allocated.  This does not represent the real state of the VMA, which is
detached until it is added into mm's VMA tree.  Fix this by marking new
VMAs as detached and resetting detached flag only after VMA is added into
a tree.

Introduce vma_mark_attached() to make the API more readable and to
simplify possible future cleanup when vma->vm_mm might be used to indicate
detached vma and vma_mark_attached() will need an additional mm parameter.

Link: https://lkml.kernel.org/r/20250213224655.1680278-4-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Tested-by: Shivank Garg <shivankg@amd.com>
  Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index 4506e6fb3c6fa..f93f7f74f97b2 100644
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -471,12 +471,16 @@ static inline void vma_lock_init(struct vm_area_struct *vma)
 }
 
 static inline void vma_assert_write_locked(struct vm_area_struct *);
-static inline void vma_mark_detached(struct vm_area_struct *vma, bool detached)
+static inline void vma_mark_attached(struct vm_area_struct *vma)
+{
+	vma->detached = false;
+}
+
+static inline void vma_mark_detached(struct vm_area_struct *vma)
 {
 	/* When detaching vma should be write-locked */
-	if (detached)
-		vma_assert_write_locked(vma);
-	vma->detached = detached;
+	vma_assert_write_locked(vma);
+	vma->detached = true;
 }
 
 extern const struct vm_operations_struct vma_dummy_vm_ops;
@@ -489,7 +493,8 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 	vma->vm_mm = mm;
 	vma->vm_ops = &vma_dummy_vm_ops;
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
-	vma_mark_detached(vma, false);
+	/* vma is not locked, can't use vma_mark_detached() */
+	vma->detached = true;
 	vma_lock_init(vma);
 }
 
@@ -515,6 +520,8 @@ static inline struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 	memcpy(new, orig, sizeof(*new));
 	vma_lock_init(new);
 	INIT_LIST_HEAD(&new->anon_vma_chain);
+	/* vma is not locked, can't use vma_mark_detached() */
+	new->detached = true;
 
 	return new;
 }