[PATCH DRAFT RFC UNTESTED 16/18] fs: userfaultfd

[Christian Brauner <brauner@kernel.org>]

Placeholder commit message.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/userfaultfd.c | 29 +++++++++--------------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..77048b86d781 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -2111,9 +2111,7 @@ static void init_once_userfaultfd_ctx(void *mem)
 
 static int new_userfaultfd(int flags)
 {
-	struct userfaultfd_ctx *ctx;
-	struct file *file;
-	int fd;
+	struct userfaultfd_ctx *ctx __free(kfree) = NULL;
 
 	VM_WARN_ON_ONCE(!current->mm);
 
@@ -2135,26 +2133,17 @@ static int new_userfaultfd(int flags)
 	atomic_set(&ctx->mmap_changing, 0);
 	ctx->mm = current->mm;
 
-	fd = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
-	if (fd < 0)
-		goto err_out;
+	FD_PREPARE(fdprep, flags & UFFD_SHARED_FCNTL_FLAGS,
+		   anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
+					     O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL));
+	if (fd_prepare_failed(fdprep))
+		return fd_prepare_error(fdprep);
 
-	/* Create a new inode so that the LSM can block the creation.  */
-	file = anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
-			O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		fd = PTR_ERR(file);
-		goto err_out;
-	}
 	/* prevent the mm struct to be freed */
 	mmgrab(ctx->mm);
-	file->f_mode |= FMODE_NOWAIT;
-	fd_install(fd, file);
-	return fd;
-err_out:
-	kmem_cache_free(userfaultfd_ctx_cachep, ctx);
-	return fd;
+	fd_prepare_file(fdprep)->f_mode |= FMODE_NOWAIT;
+	retain_and_null_ptr(ctx);
+	return fd_publish(fdprep);
 }
 
 static inline bool userfaultfd_syscall_allowed(int flags)

-- 
2.47.3