mm: rename call_mmap/mmap_prepare to vfs_mmap/mmap_prepare

The call_mmap() function violates the existing convention in
include/linux/fs.h whereby invocations of virtual file system hooks is
performed by functions prefixed with vfs_xxx().

Correct this by renaming call_mmap() to vfs_mmap(). This also avoids
confusion as to the fact that f_op->mmap_prepare may be invoked here.

Also rename __call_mmap_prepare() function to vfs_mmap_prepare() and adjust
to accept a file parameter, this is useful later for nested file systems.

Finally, fix up the VMA userland tests and ensure the mmap_prepare -> mmap
shim is implemented there.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/8d389f4994fa736aa8f9172bef8533c10a9e9011.1750099179.git.lorenzo.stoakes@oracle.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: lorenzo-stoakes

drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c

@@ -105,7 +105,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
 	if (!obj->base.filp)
 		return -ENODEV;
 
-	ret = call_mmap(obj->base.filp, vma);
+	ret = vfs_mmap(obj->base.filp, vma);
 	if (ret)
 		return ret;
 

fs/backing-file.c

@@ -339,7 +339,7 @@ int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 	vma_set_file(vma, file);
 
 	old_cred = override_creds(ctx->cred);
-	ret = call_mmap(vma->vm_file, vma);
+	ret = vfs_mmap(vma->vm_file, vma);
 	revert_creds(old_cred);
 
 	if (ctx->accessed)

fs/coda/file.c

@@ -199,10 +199,10 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
 	spin_unlock(&cii->c_lock);
 
 	vma->vm_file = get_file(host_file);
-	ret = call_mmap(vma->vm_file, vma);
+	ret = vfs_mmap(vma->vm_file, vma);
 
 	if (ret) {
-		/* if call_mmap fails, our caller will put host_file so we
+		/* if vfs_mmap fails, our caller will put host_file so we
 		 * should drop the reference to the coda_file that we got.
 		 */
 		fput(coda_file);

include/linux/fs.h

@@ -2276,16 +2276,15 @@ static inline bool file_has_valid_mmap_hooks(struct file *file)
 
 int compat_vma_mmap_prepare(struct file *file, struct vm_area_struct *vma);
 
-static inline int call_mmap(struct file *file, struct vm_area_struct *vma)
+static inline int vfs_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	if (file->f_op->mmap_prepare)
 		return compat_vma_mmap_prepare(file, vma);
 
 	return file->f_op->mmap(file, vma);
 }
 
-static inline int __call_mmap_prepare(struct file *file,
-		struct vm_area_desc *desc)
+static inline int vfs_mmap_prepare(struct file *file, struct vm_area_desc *desc)
 {
 	return file->f_op->mmap_prepare(desc);
 }

ipc/shm.c

@@ -602,7 +602,7 @@ static int shm_mmap(struct file *file, struct vm_area_struct *vma)
 	if (ret)
 		return ret;
 
-	ret = call_mmap(sfd->file, vma);
+	ret = vfs_mmap(sfd->file, vma);
 	if (ret) {
 		__shm_close(sfd);
 		return ret;

mm/internal.h

@@ -164,7 +164,7 @@ static inline void *folio_raw_mapping(const struct folio *folio)
  */
 static inline int mmap_file(struct file *file, struct vm_area_struct *vma)
 {
-	int err = call_mmap(file, vma);
+	int err = vfs_mmap(file, vma);
 
 	if (likely(!err))
 		return 0;

mm/vma.c

@@ -2569,7 +2569,7 @@ static int call_mmap_prepare(struct mmap_state *map)
 	};
 
 	/* Invoke the hook. */
-	err = __call_mmap_prepare(map->file, &desc);
+	err = vfs_mmap_prepare(map->file, &desc);
 	if (err)
 		return err;
 

tools/testing/vma/vma_internal.h

@@ -1442,6 +1442,27 @@ static inline void free_anon_vma_name(struct vm_area_struct *vma)
 	(void)vma;
 }
 
+/* Declared in vma.h. */
+static inline void set_vma_from_desc(struct vm_area_struct *vma,
+		struct vm_area_desc *desc);
+
+static inline struct vm_area_desc *vma_to_desc(struct vm_area_struct *vma,
+		struct vm_area_desc *desc);
+
+static int compat_vma_mmap_prepare(struct file *file,
+		struct vm_area_struct *vma)
+{
+	struct vm_area_desc desc;
+	int err;
+
+	err = file->f_op->mmap_prepare(vma_to_desc(vma, &desc));
+	if (err)
+		return err;
+	set_vma_from_desc(vma, &desc);
+
+	return 0;
+}
+
 /* Did the driver provide valid mmap hook configuration? */
 static inline bool file_has_valid_mmap_hooks(struct file *file)
 {
@@ -1451,22 +1472,21 @@ static inline bool file_has_valid_mmap_hooks(struct file *file)
 	/* Hooks are mutually exclusive. */
 	if (WARN_ON_ONCE(has_mmap && has_mmap_prepare))
 		return false;
-	if (WARN_ON_ONCE(!has_mmap && !has_mmap_prepare))
+	if (!has_mmap && !has_mmap_prepare)
 		return false;
 
 	return true;
 }
 
-static inline int call_mmap(struct file *file, struct vm_area_struct *vma)
+static inline int vfs_mmap(struct file *file, struct vm_area_struct *vma)
 {
-	if (WARN_ON_ONCE(file->f_op->mmap_prepare))
-		return -EINVAL;
+	if (file->f_op->mmap_prepare)
+		return compat_vma_mmap_prepare(file, vma);
 
 	return file->f_op->mmap(file, vma);
 }
 
-static inline int __call_mmap_prepare(struct file *file,
-		struct vm_area_desc *desc)
+static inline int vfs_mmap_prepare(struct file *file, struct vm_area_desc *desc)
 {
 	return file->f_op->mmap_prepare(desc);
 }