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Commit 284cd241 authored by Eric Biggers's avatar Eric Biggers Committed by Linus Torvalds
Browse files

userfaultfd: convert to use anon_inode_getfd() 

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.

Link: http://lkml.kernel.org/r/20171229212403.22800-1-ebiggers3@gmail.com


Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarMike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c5c63835

fs/userfaultfd.c

+9 −61
Original line number Diff line number Diff line
@@ -988,24 +988,14 @@ 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;

}
@@ -1887,24 +1877,10 @@ 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);
@@ -1912,14 +1888,12 @@ 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;
@@ -1930,39 +1904,13 @@ 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,

	fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,

			      O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));

	if (IS_ERR(file)) {

	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)