linux-kernel - [RFC PATCH 2/3] mm: secretmem: convert to .mmap

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Message-ID: <7bd9f0abd33677faa7d9aaeabede8d310f361a16.1746040540.git.lorenzo.stoakes@oracle.com>
Date: Wed, 30 Apr 2025 20:54:12 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan --cc=Michal Hocko <"surenb@...gle.commhocko"@suse.com>,
	Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>
Subject: [RFC PATCH 2/3] mm: secretmem: convert to .mmap_proto() hook

Secretmem has a simple .mmap() hook which is easily converted to the new
.mmap_proto() callback.

In addition, importantly, it's a rare instance of a mergeable VMA mapping
which adjusts parameters which affect merge compatibility. By using the
.mmap_proto() callback there's no longer any need to retry the merge later
as we can simply set the correct flags from the start.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 mm/secretmem.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 1b0a214ee558..64fc0890a28b 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -120,18 +120,18 @@ static int secretmem_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
-static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
+static int secretmem_mmap_proto(struct vma_proto *proto)
 {
-	unsigned long len = vma->vm_end - vma->vm_start;
+	unsigned long len = proto->end - proto->start;
 
-	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+	if ((proto->flags & (VM_SHARED | VM_MAYSHARE)) == 0)
 		return -EINVAL;
 
-	if (!mlock_future_ok(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
+	if (!mlock_future_ok(proto->mm, proto->flags | VM_LOCKED, len))
 		return -EAGAIN;
 
-	vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP);
-	vma->vm_ops = &secretmem_vm_ops;
+	proto->flags |= VM_LOCKED | VM_DONTDUMP;
+	proto->vm_ops = &secretmem_vm_ops;
 
 	return 0;
 }
@@ -143,7 +143,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma)
 
 static const struct file_operations secretmem_fops = {
 	.release	= secretmem_release,
-	.mmap		= secretmem_mmap,
+	.mmap_proto	= secretmem_mmap_proto,
 };
 
 static int secretmem_migrate_folio(struct address_space *mapping,
-- 
2.49.0