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userfaultfd: convert to use anon_inode_getfd()

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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: Eric Biggers <ebiggers@google.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Biggers 2018-01-31 16:19:48 -08:00 committed by Linus Torvalds
parent c5c63835e5
commit 284cd241a1
1 changed files with 9 additions and 61 deletions
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70
fs/userfaultfd.c
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@ -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,
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)