On Fri, Dec 29, 2017 at 03:24:03PM -0600, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> Nothing actually calls userfaultfd_file_create() besides the
> userfaultfd() system call itself. So simplify things by folding it into
> the system call and using anon_inode_getfd() instead of
> anon_inode_getfile(). Do the same in resolve_userfault_fork() as well.
> This removes over 50 lines with no change in functionality.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> ---
> fs/userfaultfd.c | 70 ++++++++------------------------------------------------
> 1 file changed, 9 insertions(+), 61 deletions(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 41a75f9f23fd..b87cc2c5cfb1 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -985,24 +985,14 @@ static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
> struct uffd_msg *msg)
> {
> int fd;
> - struct file *file;
> - unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS;
>
> - fd = get_unused_fd_flags(flags);
> + fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new,
> + O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS));
> if (fd < 0)
> return fd;
>
> - file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new,
> - O_RDWR | flags);
> - if (IS_ERR(file)) {
> - put_unused_fd(fd);
> - return PTR_ERR(file);
> - }
> -
> - fd_install(fd, file);
> msg->arg.reserved.reserved1 = 0;
> msg->arg.fork.ufd = fd;
> -
> return 0;
> }
>
> @@ -1884,24 +1874,10 @@ static void init_once_userfaultfd_ctx(void *mem)
> seqcount_init(&ctx->refile_seq);
> }
>
> -/**
> - * userfaultfd_file_create - Creates a userfaultfd file pointer.
> - * @flags: Flags for the userfaultfd file.
> - *
> - * This function creates a userfaultfd file pointer, w/out installing
> - * it into the fd table. This is useful when the userfaultfd file is
> - * used during the initialization of data structures that require
> - * extra setup after the userfaultfd creation. So the userfaultfd
> - * creation is split into the file pointer creation phase, and the
> - * file descriptor installation phase. In this way races with
> - * userspace closing the newly installed file descriptor can be
> - * avoided. Returns a userfaultfd file pointer, or a proper error
> - * pointer.
> - */
> -static struct file *userfaultfd_file_create(int flags)
> +SYSCALL_DEFINE1(userfaultfd, int, flags)
> {
> - struct file *file;
> struct userfaultfd_ctx *ctx;
> + int fd;
>
> BUG_ON(!current->mm);
>
> @@ -1909,14 +1885,12 @@ static struct file *userfaultfd_file_create(int flags)
> BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
> BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
>
> - file = ERR_PTR(-EINVAL);
> if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
> - goto out;
> + return -EINVAL;
>
> - file = ERR_PTR(-ENOMEM);
> ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
> if (!ctx)
> - goto out;
> + return -ENOMEM;
>
> atomic_set(&ctx->refcount, 1);
> ctx->flags = flags;
> @@ -1927,39 +1901,13 @@ static struct file *userfaultfd_file_create(int flags)
> /* prevent the mm struct to be freed */
> mmgrab(ctx->mm);
>
> - file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
> - O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
> - if (IS_ERR(file)) {
> + fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
> + O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
> + if (fd < 0) {
> mmdrop(ctx->mm);
> kmem_cache_free(userfaultfd_ctx_cachep, ctx);
> }
> -out:
> - return file;
> -}
> -
> -SYSCALL_DEFINE1(userfaultfd, int, flags)
> -{
> - int fd, error;
> - struct file *file;
> -
> - error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
> - if (error < 0)
> - return error;
> - fd = error;
> -
> - file = userfaultfd_file_create(flags);
> - if (IS_ERR(file)) {
> - error = PTR_ERR(file);
> - goto err_put_unused_fd;
> - }
> - fd_install(fd, file);
> -
> return fd;
> -
> -err_put_unused_fd:
> - put_unused_fd(fd);
> -
> - return error;
> }
>
> static int __init userfaultfd_init(void)
> --
> 2.15.1
>
> --
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--
Sincerely yours,
Mike.
