mm: secretmem: convert to .mmap_prepare() hook

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

Importantly, it's a rare instance of an driver that manipulates a VMA
which is mergeable (that is, not a VM_SPECIAL mapping) while also
adjusting VMA flags which may adjust mergeability, meaning the retry merge
logic might impact whether or not the VMA is merged.

By using .mmap_prepare() there's no longer any need to retry the merge
later as we can simply set the correct flags from the start.

This change therefore allows us to remove the retry merge logic in a
subsequent commit.

Link: https://lkml.kernel.org/r/0f758474fa6a30197bdf25ba62f898a69d84eef3.1746792520.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 1b0a214ee5580e659148cb930d282bde4d19112b..589b26c2d553c761648c32bcfda27590505f7334 100644 (file)
--- 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_prepare(struct vm_area_desc *desc)
 {
-       unsigned long len = vma->vm_end - vma->vm_start;
+       const unsigned long len = desc->end - desc->start;
 
-       if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
+       if ((desc->vm_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(desc->mm, desc->vm_flags | VM_LOCKED, len))
                return -EAGAIN;
 
-       vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP);
-       vma->vm_ops = &secretmem_vm_ops;
+       desc->vm_flags |= VM_LOCKED | VM_DONTDUMP;
+       desc->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_prepare   = secretmem_mmap_prepare,
 };
 
 static int secretmem_migrate_folio(struct address_space *mapping,