[PATCH RFC v3 00/47] file: add and convert to FD_PREPARE()

[PATCH RFC v3 00/47] file: add and convert to FD_PREPARE()

[Christian Brauner]

Hey,

I've been playing with this to allow for moderately flexible usage of
the get_unused_fd_flags() + create file + fd_install() pattern that's
used quite extensively.

How callers allocate files is really heterogenous so it's not really
convenient to fold them into a single class. It's possibe to split them
into subclasses like for anon inodes. I think that's not necessarily
nice as well.

My take is to add a FD_PREPARE() primitive that integrates tightly with
the new ACQUIRE_ERR() scheme that was recently added by peterz:

FD_PREPARE(fdf, open_flag, file_open_handle(&path, open_flag));
ret = ACQUIRE_ERR(fd_prepare, &fdf);
if (ret)
	return ret;

return fd_publish(fdf);

I've converted all of the easy cases over to it and it gets rid of a lot
of convoluted cleanup logic.

It's centered around struct fd_prepare. FD_PREPARE() encapsulates all of
allocation and cleanup logic and must be followed by a call to
fd_publish() which associates the fd with the file and installs it into
the callers fdtable. If fd_publish() isn't called both are deallocated.

It mandates a specific order namely that first we allocate the fd and
then instantiate the file. But that shouldn't be a problem nearly
everyone I've converted uses this exact pattern anyway.

There's a bunch of additional cases where it would be easy to convert
them to this pattern. For example, the whole sync file stuff in dma
currently retains the containing structure of the file instead of the
file itself even though it's only used to allocate files. Changing that
would make it fall into the FD_PREPARE() pattern easily. I've not done
that work yet.

There's room for extending this in a way that wed'd have subclasses for
some particularly often use patterns but as I said I'm not even sure
that's worth it.

Anyway, I'm not a macro wizard per se so maybe I missed some very
obvious bugs. Expect there to still be rough edges.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
Changes in v3:
- Remove scope-based variant.
- Link to v2: https://patch.msgid.link/20251120-work-fd-prepare-v2-0-fef6ebda05d3@kernel.org

Changes in v2:
- Make FD_PREPARE() use a separate scope.
- Convert most easy cases.
- Link to v1: https://patch.msgid.link/20251118-work-fd-prepare-v1-0-c20504d97375@kernel.org

---
Christian Brauner (47):
      file: add FD_PREPARE()
      anon_inodes: convert __anon_inode_getfd() to FD_PREPARE()
      eventfd: convert do_eventfd() to FD_PREPARE()
      fhandle: convert do_handle_open() to FD_PREPARE()
      namespace: convert open_tree() to FD_PREPARE()
      namespace: convert open_tree_attr() to FD_PREPARE()
      namespace: convert fsmount() to FD_PREPARE()
      fanotify: convert fanotify_init() to FD_PREPARE()
      nsfs: convert open_namespace() to FD_PREPARE()
      nsfs: convert ns_ioctl() to FD_PREPARE()
      autofs: convert autofs_dev_ioctl_open_mountpoint() to FD_PREPARE()
      eventpoll: convert do_epoll_create() to FD_PREPARE()
      open: convert do_sys_openat2() to FD_PREPARE()
      signalfd: convert do_signalfd4() to FD_PREPARE()
      timerfd: convert timerfd_create() to FD_PREPARE()
      userfaultfd: convert new_userfaultfd() to FD_PREPARE()
      xfs: convert xfs_open_by_handle() to FD_PREPARE()
      dma: convert dma_buf_fd() to FD_PREPARE()
      af_unix: convert unix_file_open() to FD_PREPARE()
      dma: convert sync_file_ioctl_merge() to FD_PREPARE()
      exec: convert begin_new_exec() to FD_PREPARE()
      ipc: convert do_mq_open() to FD_PREPARE()
      bpf: convert bpf_iter_new_fd() to FD_PREPARE()
      bpf: convert bpf_token_create() to FD_PREPARE()
      memfd: convert memfd_create() to FD_PREPARE()
      secretmem: convert memfd_secret() to FD_PREPARE()
      net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()
      net/kcm: convert kcm_ioctl() to FD_PREPARE()
      net/sctp: convert sctp_getsockopt_peeloff_common() to FD_PREPARE()
      net/socket: convert sock_map_fd() to FD_PREPARE()
      net/socket: convert __sys_accept4_file() to FD_PREPARE()
      spufs: convert spufs_context_open() to FD_PREPARE()
      papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE()
      spufs: convert spufs_gang_open() to FD_PREPARE()
      pseries: convert papr_platform_dump_create_handle() to FD_PREPARE()
      pseries: port papr_rtas_setup_file_interface() to FD_PREPARE()
      dma: port sw_sync_ioctl_create_fence() to FD_PREPARE()
      gpio: convert linehandle_create() to FD_PREPARE()
      hv: convert mshv_ioctl_create_partition() to FD_PREPARE()
      media: convert media_request_alloc() to FD_PREPARE()
      ntsync: convert ntsync_obj_get_fd() to FD_PREPARE()
      tty: convert ptm_open_peer() to FD_PREPARE()
      vfio: convert vfio_group_ioctl_get_device_fd() to FD_PREPARE()
      file: convert replace_fd() to FD_PREPARE()
      io_uring: convert io_create_mock_file() to FD_PREPARE()
      kvm: convert kvm_arch_supports_gmem_init_shared() to FD_PREPARE()
      kvm: convert kvm_vcpu_ioctl_get_stats_fd() to FD_PREPARE()

 arch/powerpc/platforms/cell/spufs/inode.c          | 38 +++------
 arch/powerpc/platforms/pseries/papr-hvpipe.c       | 37 +++------
 .../powerpc/platforms/pseries/papr-platform-dump.c | 39 +++------
 arch/powerpc/platforms/pseries/papr-rtas-common.c  | 32 +++-----
 drivers/dma-buf/dma-buf.c                          | 14 ++--
 drivers/dma-buf/sw_sync.c                          | 42 ++++------
 drivers/dma-buf/sync_file.c                        | 54 +++++--------
 drivers/gpio/gpiolib-cdev.c                        | 61 +++++++-------
 drivers/hv/mshv_root_main.c                        | 30 ++-----
 drivers/media/mc/mc-request.c                      | 33 +++-----
 drivers/misc/ntsync.c                              | 22 ++----
 drivers/tty/pty.c                                  | 34 +++-----
 drivers/vfio/group.c                               | 27 ++-----
 fs/anon_inodes.c                                   | 25 ++----
 fs/autofs/dev-ioctl.c                              | 34 +++-----
 fs/eventfd.c                                       | 33 +++-----
 fs/eventpoll.c                                     | 33 +++-----
 fs/exec.c                                          |  8 +-
 fs/fhandle.c                                       | 31 ++++----
 fs/file.c                                          | 20 +++--
 fs/namespace.c                                     | 92 ++++++++--------------
 fs/notify/fanotify/fanotify_user.c                 | 63 ++++++---------
 fs/nsfs.c                                          | 51 +++++-------
 fs/open.c                                          | 21 ++---
 fs/signalfd.c                                      | 29 +++----
 fs/timerfd.c                                       | 30 +++----
 fs/userfaultfd.c                                   | 32 +++-----
 fs/xfs/xfs_handle.c                                | 53 ++++---------
 include/linux/cleanup.h                            |  7 ++
 include/linux/file.h                               | 75 ++++++++++++++++++
 io_uring/mock_file.c                               | 46 ++++-------
 ipc/mqueue.c                                       | 34 +++-----
 kernel/bpf/bpf_iter.c                              | 30 +++----
 kernel/bpf/token.c                                 | 48 ++++-------
 mm/memfd.c                                         | 32 +++-----
 mm/secretmem.c                                     | 23 ++----
 net/handshake/netlink.c                            | 32 ++++----
 net/kcm/kcmsock.c                                  | 24 ++----
 net/sctp/socket.c                                  | 89 ++++++---------------
 net/socket.c                                       | 38 +++------
 net/unix/af_unix.c                                 | 20 ++---
 virt/kvm/guest_memfd.c                             | 37 +++------
 virt/kvm/kvm_main.c                                | 24 +++---
 43 files changed, 597 insertions(+), 980 deletions(-)
---
base-commit: c8e00cdc7425d5c60fd1ce6e7f71e5fb1b236991
change-id: 20251118-work-fd-prepare-f415a3bf5fda

[PATCH RFC v3 01/47] file: add FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 include/linux/cleanup.h |  7 +++++
 include/linux/file.h    | 75 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 19c7e475d3a4..b8bd2f15f91f 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -261,6 +261,10 @@ const volatile void * __must_check_fn(const volatile void *val)
  * CLASS(name, var)(args...):
  *	declare the variable @var as an instance of the named class
  *
+ * CLASS_INIT(name, var, init_expr):
+ *	declare the variable @var as an instance of the named class with
+ *	custom initialization expression.
+ *
  * Ex.
  *
  * DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd)
@@ -290,6 +294,9 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 	class_##_name##_t var __cleanup(class_##_name##_destructor) =	\
 		class_##_name##_constructor
 
+#define CLASS_INIT(_name, _var, _init_expr)                             \
+        class_##_name##_t _var __cleanup(class_##_name##_destructor) = (_init_expr)
+
 #define __scoped_class(_name, var, _label, args...)        \
 	for (CLASS(_name, var)(args); ; ({ goto _label; })) \
 		if (0) {                                   \
diff --git a/include/linux/file.h b/include/linux/file.h
index af1768d934a0..ec90bbf9eb40 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -127,4 +127,79 @@ extern void __fput_sync(struct file *);
 
 extern unsigned int sysctl_nr_open_min, sysctl_nr_open_max;
 
+/*
+ * class_fd_prepare_t: Combined fd + file allocation cleanup class.
+ *
+ * Allocates an fd and a file together. On error paths, automatically cleans
+ * up whichever resource was successfully allocated. Allows flexible file
+ * allocation with different functions per usage.
+ */
+typedef struct {
+	int fd;
+	struct file *file;
+} class_fd_prepare_t;
+
+#define fd_prepare_fd(_T) ((_T).fd)
+#define fd_prepare_file(_T) ((_T).file)
+
+static inline void class_fd_prepare_destructor(class_fd_prepare_t *_T)
+{
+	if (unlikely(_T->fd >= 0)) {
+		put_unused_fd(_T->fd);
+		if (unlikely(!IS_ERR_OR_NULL(_T->file)))
+			fput(_T->file);
+	}
+}
+
+static inline int class_fd_prepare_lock_err(class_fd_prepare_t *_T)
+{
+	if (IS_ERR(_T->file))
+		return PTR_ERR(_T->file);
+	if (unlikely(!_T->file))
+		return -ENOMEM;
+	return 0;
+}
+
+/*
+ * __FD_PREPARE_INIT(fd_flags, file_init_expr):
+ *     Helper to initialize fd_prepare class.
+ * @fd_flags: flags for get_unused_fd_flags()
+ * @file_init_expr: expression that returns struct file *
+ *
+ * Returns a struct fd_prepare with fd and file set.
+ * If fd allocation fails, file will be set to ERR_PTR with the error code.
+ * If fd succeeds but file_init_expr fails, file will contain the ERR_PTR.
+ * The file pointer is the single source of truth for error checking.
+ */
+#define __FD_PREPARE_INIT(_fd_flags, _file_init_owned)              \
+	({                                                          \
+		class_fd_prepare_t _fd_prepare = {                  \
+			.fd = get_unused_fd_flags((_fd_flags)),     \
+		};                                                  \
+		if (likely(_fd_prepare.fd >= 0))                    \
+			_fd_prepare.file = (_file_init_owned);      \
+		else                                                \
+			_fd_prepare.file = ERR_PTR(_fd_prepare.fd); \
+		_fd_prepare;                                        \
+	})
+
+/*
+ * FD_PREPARE(var, fd_flags, file_init_owned):
+ *     Declares and initializes an fd_prepare variable with automatic cleanup.
+ *     No separate scope required - cleanup happens when variable goes out of scope.
+ *
+ * @_var: name of struct fd_prepare variable to define
+ * @_fd_flags: flags for get_unused_fd_flags()
+ * @_file_init_owned: struct file to take ownership of (can be expression)
+ */
+#define FD_PREPARE(_var, _fd_flags, _file_init_owned) \
+	CLASS_INIT(fd_prepare, _var, __FD_PREPARE_INIT(_fd_flags, _file_init_owned))
+
+#define fd_publish(_fd_prepare)                           \
+	({                                                \
+		class_fd_prepare_t *__p = &(_fd_prepare); \
+		fd_install(__p->fd, __p->file);           \
+		take_fd(__p->fd);                         \
+	})
+
 #endif /* __LINUX_FILE_H */

-- 
2.47.3

[PATCH RFC v3 02/47] anon_inodes: convert __anon_inode_getfd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/anon_inodes.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 180a458fc4f7..5b15547ca693 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -280,27 +280,14 @@ static int __anon_inode_getfd(const char *name,
 			      const struct inode *context_inode,
 			      bool make_inode)
 {
-	int error, fd;
-	struct file *file;
+	int error;
 
-	error = get_unused_fd_flags(flags);
-	if (error < 0)
+	FD_PREPARE(fdf, flags, __anon_inode_getfile(name, fops, priv, flags,
+						    context_inode, make_inode));
+	error = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (error)
 		return error;
-	fd = error;
-
-	file = __anon_inode_getfile(name, fops, priv, flags, context_inode,
-				    make_inode);
-	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;
+	return fd_publish(fdf);
 }
 
 /**

-- 
2.47.3

[PATCH RFC v3 03/47] eventfd: convert do_eventfd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/eventfd.c | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index af42b2c7d235..089eff8894ea 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -378,9 +378,8 @@ EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
 
 static int do_eventfd(unsigned int count, int flags)
 {
-	struct eventfd_ctx *ctx;
-	struct file *file;
-	int fd;
+	struct eventfd_ctx *ctx __free(kfree) = NULL;
+	int err;
 
 	/* Check the EFD_* constants for consistency.  */
 	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
@@ -398,26 +397,20 @@ static int do_eventfd(unsigned int count, int flags)
 	init_waitqueue_head(&ctx->wqh);
 	ctx->count = count;
 	ctx->flags = flags;
-	ctx->id = ida_alloc(&eventfd_ida, GFP_KERNEL);
 
 	flags &= EFD_SHARED_FCNTL_FLAGS;
 	flags |= O_RDWR;
-	fd = get_unused_fd_flags(flags);
-	if (fd < 0)
-		goto err;
-
-	file = anon_inode_getfile_fmode("[eventfd]", &eventfd_fops,
-					ctx, flags, FMODE_NOWAIT);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		fd = PTR_ERR(file);
-		goto err;
-	}
-	fd_install(fd, file);
-	return fd;
-err:
-	eventfd_free_ctx(ctx);
-	return fd;
+
+	FD_PREPARE(fdf, flags,
+		   anon_inode_getfile_fmode("[eventfd]", &eventfd_fops, ctx,
+					    flags, FMODE_NOWAIT));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
+
+	ctx->id = ida_alloc(&eventfd_ida, GFP_KERNEL);
+	retain_and_null_ptr(ctx);
+	return fd_publish(fdf);
 }
 
 SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)

-- 
2.47.3

[PATCH RFC v3 04/47] fhandle: convert do_handle_open() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/fhandle.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/fs/fhandle.c b/fs/fhandle.c
index 052f9c9368fb..e3d6253b1ebd 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -404,32 +404,33 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
 	return retval;
 }
 
+static struct file *file_open_handle(struct path *path, int open_flag)
+{
+	const struct export_operations *eops;
+
+	eops = path->mnt->mnt_sb->s_export_op;
+	if (eops->open)
+		return eops->open(path, open_flag);
+
+	return file_open_root(path, "", open_flag, 0);
+}
+
 static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
 			   int open_flag)
 {
 	long retval = 0;
 	struct path path __free(path_put) = {};
-	struct file *file;
-	const struct export_operations *eops;
 
 	retval = handle_to_path(mountdirfd, ufh, &path, open_flag);
 	if (retval)
 		return retval;
 
-	CLASS(get_unused_fd, fd)(open_flag);
-	if (fd < 0)
-		return fd;
-
-	eops = path.mnt->mnt_sb->s_export_op;
-	if (eops->open)
-		file = eops->open(&path, open_flag);
-	else
-		file = file_open_root(&path, "", open_flag, 0);
-	if (IS_ERR(file))
-		return PTR_ERR(file);
+	FD_PREPARE(fdf, open_flag, file_open_handle(&path, open_flag));
+	retval = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (retval)
+		return retval;
 
-	fd_install(fd, file);
-	return take_fd(fd);
+	return fd_publish(fdf);
 }
 
 /**

-- 
2.47.3

[PATCH RFC v3 05/47] namespace: convert open_tree() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/namespace.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index d82910f33dc4..cff0fdc27fda 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3103,19 +3103,14 @@ static struct file *vfs_open_tree(int dfd, const char __user *filename, unsigned
 
 SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
 {
-	int fd;
-	struct file *file __free(fput) = NULL;
-
-	file = vfs_open_tree(dfd, filename, flags);
-	if (IS_ERR(file))
-		return PTR_ERR(file);
+	int ret;
 
-	fd = get_unused_fd_flags(flags & O_CLOEXEC);
-	if (fd < 0)
-		return fd;
+	FD_PREPARE(fdf, flags, vfs_open_tree(dfd, filename, flags));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
-	fd_install(fd, no_free_ptr(file));
-	return fd;
+	return fd_publish(fdf);
 }
 
 /*

-- 
2.47.3

[PATCH RFC v3 06/47] namespace: convert open_tree_attr() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/namespace.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index cff0fdc27fda..74157dd471ee 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5030,19 +5030,19 @@ SYSCALL_DEFINE5(open_tree_attr, int, dfd, const char __user *, filename,
 		unsigned, flags, struct mount_attr __user *, uattr,
 		size_t, usize)
 {
-	struct file __free(fput) *file = NULL;
-	int fd;
+	int ret;
 
 	if (!uattr && usize)
 		return -EINVAL;
 
-	file = vfs_open_tree(dfd, filename, flags);
-	if (IS_ERR(file))
-		return PTR_ERR(file);
+	FD_PREPARE(fdf, flags, vfs_open_tree(dfd, filename, flags));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
 	if (uattr) {
-		int ret;
 		struct mount_kattr kattr = {};
+		struct file *file = fd_prepare_file(fdf);
 
 		if (flags & OPEN_TREE_CLONE)
 			kattr.kflags = MOUNT_KATTR_IDMAP_REPLACE;
@@ -5058,12 +5058,7 @@ SYSCALL_DEFINE5(open_tree_attr, int, dfd, const char __user *, filename,
 			return ret;
 	}
 
-	fd = get_unused_fd_flags(flags & O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	fd_install(fd, no_free_ptr(file));
-	return fd;
+	return fd_publish(fdf);
 }
 
 int show_path(struct seq_file *m, struct dentry *root)

-- 
2.47.3

[PATCH RFC v3 07/47] namespace: convert fsmount() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/namespace.c | 56 ++++++++++++++++++++++----------------------------------
 1 file changed, 22 insertions(+), 34 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 74157dd471ee..8716aedada2c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4280,8 +4280,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 {
 	struct mnt_namespace *ns;
 	struct fs_context *fc;
-	struct file *file;
-	struct path newmount;
+	struct path newmount __free(path_put) = {};
 	struct mount *mnt;
 	unsigned int mnt_flags = 0;
 	long ret;
@@ -4319,33 +4318,32 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 
 	fc = fd_file(f)->private_data;
 
-	ret = mutex_lock_interruptible(&fc->uapi_mutex);
-	if (ret < 0)
+	ACQUIRE(mutex_intr, uapi_mutex)(&fc->uapi_mutex);
+	ret = ACQUIRE_ERR(mutex_intr, &uapi_mutex);
+	if (ret)
 		return ret;
 
 	/* There must be a valid superblock or we can't mount it */
 	ret = -EINVAL;
 	if (!fc->root)
-		goto err_unlock;
+		return ret;
 
 	ret = -EPERM;
 	if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
 		errorfcp(fc, "VFS", "Mount too revealing");
-		goto err_unlock;
+		return ret;
 	}
 
 	ret = -EBUSY;
 	if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
-		goto err_unlock;
+		return ret;
 
 	if (fc->sb_flags & SB_MANDLOCK)
 		warn_mandlock();
 
 	newmount.mnt = vfs_create_mount(fc);
-	if (IS_ERR(newmount.mnt)) {
-		ret = PTR_ERR(newmount.mnt);
-		goto err_unlock;
-	}
+	if (IS_ERR(newmount.mnt))
+		return PTR_ERR(newmount.mnt);
 	newmount.dentry = dget(fc->root);
 	newmount.mnt->mnt_flags = mnt_flags;
 
@@ -4357,38 +4355,28 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 	vfs_clean_context(fc);
 
 	ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
-	if (IS_ERR(ns)) {
-		ret = PTR_ERR(ns);
-		goto err_path;
-	}
+	if (IS_ERR(ns))
+		return PTR_ERR(ns);
 	mnt = real_mount(newmount.mnt);
 	ns->root = mnt;
 	ns->nr_mounts = 1;
 	mnt_add_to_ns(ns, mnt);
 	mntget(newmount.mnt);
 
-	/* Attach to an apparent O_PATH fd with a note that we need to unmount
-	 * it, not just simply put it.
-	 */
-	file = dentry_open(&newmount, O_PATH, fc->cred);
-	if (IS_ERR(file)) {
+	FD_PREPARE(fdf, (flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0,
+		   dentry_open(&newmount, O_PATH, fc->cred));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret) {
 		dissolve_on_fput(newmount.mnt);
-		ret = PTR_ERR(file);
-		goto err_path;
+		return ret;
 	}
-	file->f_mode |= FMODE_NEED_UNMOUNT;
-
-	ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
-	if (ret >= 0)
-		fd_install(ret, file);
-	else
-		fput(file);
 
-err_path:
-	path_put(&newmount);
-err_unlock:
-	mutex_unlock(&fc->uapi_mutex);
-	return ret;
+	/*
+	 * Attach to an apparent O_PATH fd with a note that we
+	 * need to unmount it, not just simply put it.
+	 */
+	fd_prepare_file(fdf)->f_mode |= FMODE_NEED_UNMOUNT;
+	return fd_publish(fdf);
 }
 
 static inline int vfs_move_mount(const struct path *from_path,

-- 
2.47.3

[PATCH RFC v3 08/47] fanotify: convert fanotify_init() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/notify/fanotify/fanotify_user.c | 63 +++++++++++++++-----------------------
 1 file changed, 25 insertions(+), 38 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 1dadda82cae5..80166aded1da 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1597,16 +1597,20 @@ static struct hlist_head *fanotify_alloc_merge_hash(void)
 	return hash;
 }
 
+DEFINE_CLASS(fsnotify_group,
+	      struct fsnotify_group *,
+	      if (_T) fsnotify_destroy_group(_T),
+	      fsnotify_alloc_group(ops, flags),
+	      const struct fsnotify_ops *ops, int flags)
+
 /* fanotify syscalls */
 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 {
 	struct user_namespace *user_ns = current_user_ns();
-	struct fsnotify_group *group;
 	int f_flags, fd;
 	unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
 	unsigned int class = flags & FANOTIFY_CLASS_BITS;
 	unsigned int internal_flags = 0;
-	struct file *file;
 
 	pr_debug("%s: flags=%x event_f_flags=%x\n",
 		 __func__, flags, event_f_flags);
@@ -1690,36 +1694,29 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	if (flags & FAN_NONBLOCK)
 		f_flags |= O_NONBLOCK;
 
-	/* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
-	group = fsnotify_alloc_group(&fanotify_fsnotify_ops,
+	CLASS(fsnotify_group, group)(&fanotify_fsnotify_ops,
 				     FSNOTIFY_GROUP_USER);
-	if (IS_ERR(group)) {
+	/* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
+	if (IS_ERR(group))
 		return PTR_ERR(group);
-	}
 
 	/* Enforce groups limits per user in all containing user ns */
 	group->fanotify_data.ucounts = inc_ucount(user_ns, current_euid(),
 						  UCOUNT_FANOTIFY_GROUPS);
-	if (!group->fanotify_data.ucounts) {
-		fd = -EMFILE;
-		goto out_destroy_group;
-	}
+	if (!group->fanotify_data.ucounts)
+		return -EMFILE;
 
 	group->fanotify_data.flags = flags | internal_flags;
 	group->memcg = get_mem_cgroup_from_mm(current->mm);
 	group->user_ns = get_user_ns(user_ns);
 
 	group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
-	if (!group->fanotify_data.merge_hash) {
-		fd = -ENOMEM;
-		goto out_destroy_group;
-	}
+	if (!group->fanotify_data.merge_hash)
+		return -ENOMEM;
 
 	group->overflow_event = fanotify_alloc_overflow_event();
-	if (unlikely(!group->overflow_event)) {
-		fd = -ENOMEM;
-		goto out_destroy_group;
-	}
+	if (unlikely(!group->overflow_event))
+		return -ENOMEM;
 
 	if (force_o_largefile())
 		event_f_flags |= O_LARGEFILE;
@@ -1738,8 +1735,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 		group->priority = FSNOTIFY_PRIO_PRE_CONTENT;
 		break;
 	default:
-		fd = -EINVAL;
-		goto out_destroy_group;
+		return -EINVAL;
 	}
 
 	BUILD_BUG_ON(!(FANOTIFY_ADMIN_INIT_FLAGS & FAN_UNLIMITED_QUEUE));
@@ -1750,28 +1746,19 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	}
 
 	if (flags & FAN_ENABLE_AUDIT) {
-		fd = -EPERM;
 		if (!capable(CAP_AUDIT_WRITE))
-			goto out_destroy_group;
+			return -EPERM;
 	}
 
-	fd = get_unused_fd_flags(f_flags);
-	if (fd < 0)
-		goto out_destroy_group;
+	FD_PREPARE(fdf, f_flags,
+		   anon_inode_getfile_fmode("[fanotify]", &fanotify_fops, group,
+					    f_flags, FMODE_NONOTIFY));
+	fd = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (fd)
+		return fd;
 
-	file = anon_inode_getfile_fmode("[fanotify]", &fanotify_fops, group,
-					f_flags, FMODE_NONOTIFY);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		fd = PTR_ERR(file);
-		goto out_destroy_group;
-	}
-	fd_install(fd, file);
-	return fd;
-
-out_destroy_group:
-	fsnotify_destroy_group(group);
-	return fd;
+	retain_and_null_ptr(group);
+	return fd_publish(fdf);
 }
 
 static int fanotify_test_fsid(struct dentry *dentry, unsigned int flags,

-- 
2.47.3

[PATCH RFC v3 09/47] nsfs: convert open_namespace() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/nsfs.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 79b026a36fb6..61102cc63e1d 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -108,7 +108,6 @@ int ns_get_path(struct path *path, struct task_struct *task,
 int open_namespace(struct ns_common *ns)
 {
 	struct path path __free(path_put) = {};
-	struct file *f;
 	int err;
 
 	/* call first to consume reference */
@@ -116,16 +115,11 @@ int open_namespace(struct ns_common *ns)
 	if (err < 0)
 		return err;
 
-	CLASS(get_unused_fd, fd)(O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	f = dentry_open(&path, O_RDONLY, current_cred());
-	if (IS_ERR(f))
-		return PTR_ERR(f);
-
-	fd_install(fd, f);
-	return take_fd(fd);
+	FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
+	return fd_publish(fdf);
 }
 
 int open_related_ns(struct ns_common *ns,

-- 
2.47.3

[PATCH RFC v3 10/47] nsfs: convert ns_ioctl() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/nsfs.c | 35 +++++++++++++----------------------
 1 file changed, 13 insertions(+), 22 deletions(-)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 61102cc63e1d..d4f115c4b11d 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -324,28 +324,19 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 		if (ret)
 			return ret;
 
-		CLASS(get_unused_fd, fd)(O_CLOEXEC);
-		if (fd < 0)
-			return fd;
-
-		f = dentry_open(&path, O_RDONLY, current_cred());
-		if (IS_ERR(f))
-			return PTR_ERR(f);
-
-		if (uinfo) {
-			/*
-			 * If @uinfo is passed return all information about the
-			 * mount namespace as well.
-			 */
-			ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
-			if (ret)
-				return ret;
-		}
-
-		/* Transfer reference of @f to caller's fdtable. */
-		fd_install(fd, no_free_ptr(f));
-		/* File descriptor is live so hand it off to the caller. */
-		return take_fd(fd);
+		FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
+		ret = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (ret)
+			return ret;
+		/*
+		 * If @uinfo is passed return all information about the
+		 * mount namespace as well.
+		 */
+		ret = copy_ns_info_to_user(to_mnt_ns(ns), uinfo, usize, &kinfo);
+		if (ret)
+			return ret;
+		ret = fd_publish(fdf);
+		break;
 	}
 	default:
 		ret = -ENOTTY;

-- 
2.47.3

[PATCH RFC v3 11/47] autofs: convert autofs_dev_ioctl_open_mountpoint() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/autofs/dev-ioctl.c | 34 ++++++++++------------------------
 1 file changed, 10 insertions(+), 24 deletions(-)

diff --git a/fs/autofs/dev-ioctl.c b/fs/autofs/dev-ioctl.c
index d8dd150cbd74..11a706af13af 100644
--- a/fs/autofs/dev-ioctl.c
+++ b/fs/autofs/dev-ioctl.c
@@ -231,32 +231,18 @@ static int test_by_type(const struct path *path, void *p)
  */
 static int autofs_dev_ioctl_open_mountpoint(const char *name, dev_t devid)
 {
-	int err, fd;
-
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (likely(fd >= 0)) {
-		struct file *filp;
-		struct path path;
-
-		err = find_autofs_mount(name, &path, test_by_dev, &devid);
-		if (err)
-			goto out;
-
-		filp = dentry_open(&path, O_RDONLY, current_cred());
-		path_put(&path);
-		if (IS_ERR(filp)) {
-			err = PTR_ERR(filp);
-			goto out;
-		}
-
-		fd_install(fd, filp);
-	}
+	struct path path __free(path_put) = {};
+	int err;
 
-	return fd;
+	err = find_autofs_mount(name, &path, test_by_dev, &devid);
+	if (err)
+		return err;
 
-out:
-	put_unused_fd(fd);
-	return err;
+	FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&path, O_RDONLY, current_cred()));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
+	return fd_publish(fdf);
 }
 
 /* Open a file descriptor on an autofs mount point */

-- 
2.47.3

[PATCH RFC v3 12/47] eventpoll: convert do_epoll_create() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/eventpoll.c | 33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ee7c4b683ec3..f694252d9614 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2165,9 +2165,8 @@ static void clear_tfile_check_list(void)
  */
 static int do_epoll_create(int flags)
 {
-	int error, fd;
-	struct eventpoll *ep = NULL;
-	struct file *file;
+	int error;
+	struct eventpoll *ep;
 
 	/* Check the EPOLL_* constant for consistency.  */
 	BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
@@ -2184,26 +2183,16 @@ static int do_epoll_create(int flags)
 	 * Creates all the items needed to setup an eventpoll file. That is,
 	 * a file structure and a free file descriptor.
 	 */
-	fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC));
-	if (fd < 0) {
-		error = fd;
-		goto out_free_ep;
-	}
-	file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
-				 O_RDWR | (flags & O_CLOEXEC));
-	if (IS_ERR(file)) {
-		error = PTR_ERR(file);
-		goto out_free_fd;
+	FD_PREPARE(fdf, O_RDWR | (flags & O_CLOEXEC),
+		   anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
+				      O_RDWR | (flags & O_CLOEXEC)));
+	error = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (error) {
+		ep_clear_and_put(ep);
+		return error;
 	}
-	ep->file = file;
-	fd_install(fd, file);
-	return fd;
-
-out_free_fd:
-	put_unused_fd(fd);
-out_free_ep:
-	ep_clear_and_put(ep);
-	return error;
+	ep->file = fd_prepare_file(fdf);
+	return fd_publish(fdf);
 }
 
 SYSCALL_DEFINE1(epoll_create1, int, flags)

-- 
2.47.3

[PATCH RFC v3 13/47] open: convert do_sys_openat2() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/open.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 3d64372ecc67..5b86cea07a89 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1421,8 +1421,8 @@ static int do_sys_openat2(int dfd, const char __user *filename,
 			  struct open_how *how)
 {
 	struct open_flags op;
-	struct filename *tmp;
-	int err, fd;
+	struct filename *tmp __free(putname);
+	int err;
 
 	err = build_open_flags(how, &op);
 	if (unlikely(err))
@@ -1432,18 +1432,11 @@ static int do_sys_openat2(int dfd, const char __user *filename,
 	if (IS_ERR(tmp))
 		return PTR_ERR(tmp);
 
-	fd = get_unused_fd_flags(how->flags);
-	if (likely(fd >= 0)) {
-		struct file *f = do_filp_open(dfd, tmp, &op);
-		if (IS_ERR(f)) {
-			put_unused_fd(fd);
-			fd = PTR_ERR(f);
-		} else {
-			fd_install(fd, f);
-		}
-	}
-	putname(tmp);
-	return fd;
+	FD_PREPARE(fdf, how->flags, do_filp_open(dfd, tmp, &op));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
+	return fd_publish(fdf);
 }
 
 int do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)

-- 
2.47.3

[PATCH RFC v3 14/47] signalfd: convert do_signalfd4() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/signalfd.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/fs/signalfd.c b/fs/signalfd.c
index d469782f97f4..8f1ee3c85f8d 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -250,8 +250,6 @@ static const struct file_operations signalfd_fops = {
 
 static int do_signalfd4(int ufd, sigset_t *mask, int flags)
 {
-	struct signalfd_ctx *ctx;
-
 	/* Check the SFD_* constants for consistency.  */
 	BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC);
 	BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK);
@@ -263,7 +261,8 @@ static int do_signalfd4(int ufd, sigset_t *mask, int flags)
 	signotset(mask);
 
 	if (ufd == -1) {
-		struct file *file;
+		int err;
+		struct signalfd_ctx *ctx __free(kfree) = NULL;
 
 		ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
 		if (!ctx)
@@ -271,22 +270,18 @@ static int do_signalfd4(int ufd, sigset_t *mask, int flags)
 
 		ctx->sigmask = *mask;
 
-		ufd = get_unused_fd_flags(flags & O_CLOEXEC);
-		if (ufd < 0) {
-			kfree(ctx);
-			return ufd;
-		}
+		FD_PREPARE(fdf, flags & O_CLOEXEC,
+			   anon_inode_getfile_fmode("[signalfd]", &signalfd_fops, ctx,
+						    O_RDWR | (flags & O_NONBLOCK), FMODE_NOWAIT));
+		err = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (err)
+			return err;
 
-		file = anon_inode_getfile_fmode("[signalfd]", &signalfd_fops,
-					ctx, O_RDWR | (flags & O_NONBLOCK),
-					FMODE_NOWAIT);
-		if (IS_ERR(file)) {
-			put_unused_fd(ufd);
-			kfree(ctx);
-			return PTR_ERR(file);
-		}
-		fd_install(ufd, file);
+		retain_and_null_ptr(ctx);
+		return fd_publish(fdf);
 	} else {
+		struct signalfd_ctx *ctx;
+
 		CLASS(fd, f)(ufd);
 		if (fd_empty(f))
 			return -EBADF;

-- 
2.47.3

[PATCH RFC v3 15/47] timerfd: convert timerfd_create() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/timerfd.c | 30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/fs/timerfd.c b/fs/timerfd.c
index c68f28d9c426..2ae31663cc63 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -393,9 +393,8 @@ static const struct file_operations timerfd_fops = {
 
 SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
 {
-	int ufd;
-	struct timerfd_ctx *ctx;
-	struct file *file;
+	struct timerfd_ctx *ctx __free(kfree) = NULL;
+	int ret;
 
 	/* Check the TFD_* constants for consistency.  */
 	BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
@@ -432,23 +431,16 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
 
 	ctx->moffs = ktime_mono_to_real(0);
 
-	ufd = get_unused_fd_flags(flags & TFD_SHARED_FCNTL_FLAGS);
-	if (ufd < 0) {
-		kfree(ctx);
-		return ufd;
-	}
-
-	file = anon_inode_getfile_fmode("[timerfd]", &timerfd_fops, ctx,
-			    O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS),
-			    FMODE_NOWAIT);
-	if (IS_ERR(file)) {
-		put_unused_fd(ufd);
-		kfree(ctx);
-		return PTR_ERR(file);
-	}
+	FD_PREPARE(fdf, flags & TFD_SHARED_FCNTL_FLAGS,
+		   anon_inode_getfile_fmode("[timerfd]", &timerfd_fops, ctx,
+					    O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS),
+					    FMODE_NOWAIT));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
-	fd_install(ufd, file);
-	return ufd;
+	retain_and_null_ptr(ctx);
+	return fd_publish(fdf);
 }
 
 static int do_timerfd_settime(int ufd, int flags, 

-- 
2.47.3

[PATCH RFC v3 16/47] userfaultfd: convert new_userfaultfd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/userfaultfd.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..6388a525cdb1 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -2111,9 +2111,8 @@ static void init_once_userfaultfd_ctx(void *mem)
 
 static int new_userfaultfd(int flags)
 {
-	struct userfaultfd_ctx *ctx;
-	struct file *file;
-	int fd;
+	int ret;
+	struct userfaultfd_ctx *ctx __free(kfree) = NULL;
 
 	VM_WARN_ON_ONCE(!current->mm);
 
@@ -2135,26 +2134,19 @@ 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(fdf, flags & UFFD_SHARED_FCNTL_FLAGS,
+		   anon_inode_create_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
+					     O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS),
+					     NULL));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
-	/* 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(fdf)->f_mode |= FMODE_NOWAIT;
+	retain_and_null_ptr(ctx);
+	return fd_publish(fdf);
 }
 
 static inline bool userfaultfd_syscall_allowed(int flags)

-- 
2.47.3

[PATCH RFC v3 17/47] xfs: convert xfs_open_by_handle() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/xfs/xfs_handle.c | 53 +++++++++++++++++------------------------------------
 1 file changed, 17 insertions(+), 36 deletions(-)

diff --git a/fs/xfs/xfs_handle.c b/fs/xfs/xfs_handle.c
index f19fce557354..3c1895f7009d 100644
--- a/fs/xfs/xfs_handle.c
+++ b/fs/xfs/xfs_handle.c
@@ -234,13 +234,11 @@ xfs_open_by_handle(
 {
 	const struct cred	*cred = current_cred();
 	int			error;
-	int			fd;
 	int			permflag;
-	struct file		*filp;
 	struct inode		*inode;
 	struct dentry		*dentry;
 	fmode_t			fmode;
-	struct path		path;
+	struct path		path __free(path_put) = {};
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -252,8 +250,7 @@ xfs_open_by_handle(
 
 	/* Restrict xfs_open_by_handle to directories & regular files. */
 	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) {
-		error = -EPERM;
-		goto out_dput;
+		return -EPERM;
 	}
 
 #if BITS_PER_LONG != 32
@@ -263,48 +260,32 @@ xfs_open_by_handle(
 	permflag = hreq->oflags;
 	fmode = OPEN_FMODE(permflag);
 	if ((!(permflag & O_APPEND) || (permflag & O_TRUNC)) &&
-	    (fmode & FMODE_WRITE) && IS_APPEND(inode)) {
-		error = -EPERM;
-		goto out_dput;
-	}
+	    (fmode & FMODE_WRITE) && IS_APPEND(inode))
+		return -EPERM;
 
-	if ((fmode & FMODE_WRITE) && IS_IMMUTABLE(inode)) {
-		error = -EPERM;
-		goto out_dput;
-	}
+	if ((fmode & FMODE_WRITE) && IS_IMMUTABLE(inode))
+		return -EPERM;
 
 	/* Can't write directories. */
-	if (S_ISDIR(inode->i_mode) && (fmode & FMODE_WRITE)) {
-		error = -EISDIR;
-		goto out_dput;
-	}
-
-	fd = get_unused_fd_flags(0);
-	if (fd < 0) {
-		error = fd;
-		goto out_dput;
-	}
+	if (S_ISDIR(inode->i_mode) && (fmode & FMODE_WRITE))
+		return -EISDIR;
 
-	path.mnt = parfilp->f_path.mnt;
+	path.mnt = mntget(parfilp->f_path.mnt);
 	path.dentry = dentry;
-	filp = dentry_open(&path, hreq->oflags, cred);
-	dput(dentry);
-	if (IS_ERR(filp)) {
-		put_unused_fd(fd);
-		return PTR_ERR(filp);
-	}
+
+	FD_PREPARE(fdf, 0, dentry_open(&path, hreq->oflags, cred));
+	error = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (error)
+		return error;
 
 	if (S_ISREG(inode->i_mode)) {
+		struct file *filp = fd_prepare_file(fdf);
+
 		filp->f_flags |= O_NOATIME;
 		filp->f_mode |= FMODE_NOCMTIME;
 	}
 
-	fd_install(fd, filp);
-	return fd;
-
- out_dput:
-	dput(dentry);
-	return error;
+	return fd_publish(fdf);
 }
 
 int

-- 
2.47.3

[PATCH RFC v3 18/47] dma: convert dma_buf_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/dma-buf/dma-buf.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 2bcf9ceca997..e46d8719d61b 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -768,18 +768,16 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_export, "DMA_BUF");
  */
 int dma_buf_fd(struct dma_buf *dmabuf, int flags)
 {
-	int fd;
+	int ret;
 
 	if (!dmabuf || !dmabuf->file)
 		return -EINVAL;
 
-	fd = get_unused_fd_flags(flags);
-	if (fd < 0)
-		return fd;
-
-	fd_install(fd, dmabuf->file);
-
-	return fd;
+	FD_PREPARE(fdf, flags, dmabuf->file);
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
+	return fd_publish(fdf);
 }
 EXPORT_SYMBOL_NS_GPL(dma_buf_fd, "DMA_BUF");
 

-- 
2.47.3

[PATCH RFC v3 19/47] af_unix: convert unix_file_open() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/unix/af_unix.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 68c94f49f7b5..80dd12b6b441 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -3277,8 +3277,7 @@ EXPORT_SYMBOL_GPL(unix_outq_len);
 
 static int unix_open_file(struct sock *sk)
 {
-	struct file *f;
-	int fd;
+	int ret;
 
 	if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
@@ -3289,18 +3288,11 @@ static int unix_open_file(struct sock *sk)
 	if (!unix_sk(sk)->path.dentry)
 		return -ENOENT;
 
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	f = dentry_open(&unix_sk(sk)->path, O_PATH, current_cred());
-	if (IS_ERR(f)) {
-		put_unused_fd(fd);
-		return PTR_ERR(f);
-	}
-
-	fd_install(fd, f);
-	return fd;
+	FD_PREPARE(fdf, O_CLOEXEC, dentry_open(&unix_sk(sk)->path, O_PATH, current_cred()));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
+	return fd_publish(fdf);
 }
 
 static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)

-- 
2.47.3

[PATCH RFC v3 20/47] dma: convert sync_file_ioctl_merge() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/dma-buf/sync_file.c | 54 ++++++++++++++++-----------------------------
 1 file changed, 19 insertions(+), 35 deletions(-)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 747e377fb954..842db95efddb 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -213,56 +213,40 @@ static __poll_t sync_file_poll(struct file *file, poll_table *wait)
 static long sync_file_ioctl_merge(struct sync_file *sync_file,
 				  unsigned long arg)
 {
-	int fd = get_unused_fd_flags(O_CLOEXEC);
-	int err;
 	struct sync_file *fence2, *fence3;
 	struct sync_merge_data data;
+	int err;
 
-	if (fd < 0)
-		return fd;
-
-	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
-		err = -EFAULT;
-		goto err_put_fd;
-	}
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+		return -EFAULT;
 
-	if (data.flags || data.pad) {
-		err = -EINVAL;
-		goto err_put_fd;
-	}
+	if (data.flags || data.pad)
+		return -EINVAL;
 
 	fence2 = sync_file_fdget(data.fd2);
-	if (!fence2) {
-		err = -ENOENT;
-		goto err_put_fd;
-	}
+	if (!fence2)
+		return -ENOENT;
 
 	data.name[sizeof(data.name) - 1] = '\0';
 	fence3 = sync_file_merge(data.name, sync_file, fence2);
 	if (!fence3) {
-		err = -ENOMEM;
-		goto err_put_fence2;
-	}
-
-	data.fence = fd;
-	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
-		err = -EFAULT;
-		goto err_put_fence3;
+		fput(fence2->file);
+		return -ENOMEM;
 	}
 
-	fd_install(fd, fence3->file);
+	FD_PREPARE(fdf, O_CLOEXEC, fence3->file);
 	fput(fence2->file);
-	return 0;
-
-err_put_fence3:
-	fput(fence3->file);
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err) {
+		fput(fence3->file);
+		return err;
+	}
 
-err_put_fence2:
-	fput(fence2->file);
+	data.fence = fd_prepare_fd(fdf);
+	if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+		return -EFAULT;
 
-err_put_fd:
-	put_unused_fd(fd);
-	return err;
+	return fd_publish(fdf);
 }
 
 static int sync_fill_fence_info(struct dma_fence *fence,

-- 
2.47.3

[PATCH RFC v3 21/47] exec: convert begin_new_exec() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/exec.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 4298e7e08d5d..b19bdcd6fd1e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1280,12 +1280,12 @@ int begin_new_exec(struct linux_binprm * bprm)
 
 	/* Pass the opened binary to the interpreter. */
 	if (bprm->have_execfd) {
-		retval = get_unused_fd_flags(0);
-		if (retval < 0)
+		FD_PREPARE(fdf, 0, bprm->executable);
+		retval = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (retval)
 			goto out_unlock;
-		fd_install(retval, bprm->executable);
 		bprm->executable = NULL;
-		bprm->execfd = retval;
+		bprm->execfd = fd_publish(fdf);
 	}
 	return 0;
 

-- 
2.47.3

[PATCH RFC v3 22/47] ipc: convert do_mq_open() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 ipc/mqueue.c | 34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 093551fe66a7..e9890736ba19 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -899,7 +899,7 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
 	struct dentry *root = mnt->mnt_root;
 	struct filename *name;
 	struct path path;
-	int fd, error;
+	int ret;
 	int ro;
 
 	audit_mq_open(oflag, mode, attr);
@@ -908,38 +908,30 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
 	if (IS_ERR(name))
 		return PTR_ERR(name);
 
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0)
-		goto out_putname;
-
 	ro = mnt_want_write(mnt);	/* we'll drop it in any case */
 	inode_lock(d_inode(root));
 	path.dentry = lookup_noperm(&QSTR(name->name), root);
 	if (IS_ERR(path.dentry)) {
-		error = PTR_ERR(path.dentry);
-		goto out_putfd;
+		ret = PTR_ERR(path.dentry);
+		goto out_unlock;
 	}
 	path.mnt = mntget(mnt);
-	error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
-	if (!error) {
-		struct file *file = dentry_open(&path, oflag, current_cred());
-		if (!IS_ERR(file))
-			fd_install(fd, file);
-		else
-			error = PTR_ERR(file);
+	ret = prepare_open(path.dentry, oflag, ro, mode, name, attr);
+	if (!ret) {
+		FD_PREPARE(fdf, O_CLOEXEC,
+			   dentry_open(&path, oflag, current_cred()));
+		ret = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (!ret)
+			ret = fd_publish(fdf);
 	}
 	path_put(&path);
-out_putfd:
-	if (error) {
-		put_unused_fd(fd);
-		fd = error;
-	}
+
+out_unlock:
 	inode_unlock(d_inode(root));
 	if (!ro)
 		mnt_drop_write(mnt);
-out_putname:
 	putname(name);
-	return fd;
+	return ret;
 }
 
 SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,

-- 
2.47.3

[PATCH RFC v3 23/47] bpf: convert bpf_iter_new_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 kernel/bpf/bpf_iter.c | 30 +++++++++---------------------
 1 file changed, 9 insertions(+), 21 deletions(-)

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 6ac35430c573..60f9ca339a6b 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -634,37 +634,25 @@ static int prepare_seq_file(struct file *file, struct bpf_iter_link *link)
 int bpf_iter_new_fd(struct bpf_link *link)
 {
 	struct bpf_iter_link *iter_link;
-	struct file *file;
 	unsigned int flags;
-	int err, fd;
+	int err;
 
 	if (link->ops != &bpf_iter_link_lops)
 		return -EINVAL;
 
 	flags = O_RDONLY | O_CLOEXEC;
-	fd = get_unused_fd_flags(flags);
-	if (fd < 0)
-		return fd;
-
-	file = anon_inode_getfile("bpf_iter", &bpf_iter_fops, NULL, flags);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto free_fd;
-	}
 
-	iter_link = container_of(link, struct bpf_iter_link, link);
-	err = prepare_seq_file(file, iter_link);
+	FD_PREPARE(fdf, flags, anon_inode_getfile("bpf_iter", &bpf_iter_fops, NULL, flags));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
 	if (err)
-		goto free_file;
+		return err;
 
-	fd_install(fd, file);
-	return fd;
+	iter_link = container_of(link, struct bpf_iter_link, link);
+	err = prepare_seq_file(fd_prepare_file(fdf), iter_link);
+	if (err)
+		return err; /* Automatic cleanup handles fput */
 
-free_file:
-	fput(file);
-free_fd:
-	put_unused_fd(fd);
-	return err;
+	return fd_publish(fdf);
 }
 
 struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop)

-- 
2.47.3

[PATCH RFC v3 24/47] bpf: convert bpf_token_create() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 kernel/bpf/token.c | 48 ++++++++++++++++--------------------------------
 1 file changed, 16 insertions(+), 32 deletions(-)

diff --git a/kernel/bpf/token.c b/kernel/bpf/token.c
index 0bbe412f854e..100afbe17dfa 100644
--- a/kernel/bpf/token.c
+++ b/kernel/bpf/token.c
@@ -110,16 +110,15 @@ const struct file_operations bpf_token_fops = {
 
 int bpf_token_create(union bpf_attr *attr)
 {
+	struct bpf_token *token __free(kfree) = NULL;
 	struct bpf_mount_opts *mnt_opts;
-	struct bpf_token *token = NULL;
 	struct user_namespace *userns;
 	struct inode *inode;
-	struct file *file;
 	CLASS(fd, f)(attr->token_create.bpffs_fd);
 	struct path path;
 	struct super_block *sb;
 	umode_t mode;
-	int err, fd;
+	int err;
 
 	if (fd_empty(f))
 		return -EBADF;
@@ -166,23 +165,21 @@ int bpf_token_create(union bpf_attr *attr)
 	inode->i_fop = &bpf_token_fops;
 	clear_nlink(inode); /* make sure it is unlinked */
 
-	file = alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME, O_RDWR, &bpf_token_fops);
-	if (IS_ERR(file)) {
-		iput(inode);
-		return PTR_ERR(file);
-	}
+	FD_PREPARE(fdf, O_CLOEXEC,
+		   alloc_file_pseudo(inode, path.mnt, BPF_TOKEN_INODE_NAME,
+				     O_RDWR, &bpf_token_fops));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
 
 	token = kzalloc(sizeof(*token), GFP_USER);
-	if (!token) {
-		err = -ENOMEM;
-		goto out_file;
-	}
+	if (!token)
+		return -ENOMEM;
 
 	atomic64_set(&token->refcnt, 1);
 
-	/* remember bpffs owning userns for future ns_capable() checks */
-	token->userns = get_user_ns(userns);
-
+	/* remember bpffs owning userns for future ns_capable() checks. */
+	token->userns = userns;
 	token->allowed_cmds = mnt_opts->delegate_cmds;
 	token->allowed_maps = mnt_opts->delegate_maps;
 	token->allowed_progs = mnt_opts->delegate_progs;
@@ -190,24 +187,11 @@ int bpf_token_create(union bpf_attr *attr)
 
 	err = security_bpf_token_create(token, attr, &path);
 	if (err)
-		goto out_token;
-
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0) {
-		err = fd;
-		goto out_token;
-	}
-
-	file->private_data = token;
-	fd_install(fd, file);
-
-	return fd;
+		return err;
 
-out_token:
-	bpf_token_free(token);
-out_file:
-	fput(file);
-	return err;
+	get_user_ns(token->userns);
+	fd_prepare_file(fdf)->private_data = no_free_ptr(token);
+	return fd_publish(fdf);
 }
 
 int bpf_token_get_info_by_fd(struct bpf_token *token,

-- 
2.47.3

[PATCH RFC v3 25/47] memfd: convert memfd_create() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 mm/memfd.c | 32 +++++++++-----------------------
 1 file changed, 9 insertions(+), 23 deletions(-)

diff --git a/mm/memfd.c b/mm/memfd.c
index 1d109c1acf21..4267ab8e9099 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -470,9 +470,9 @@ SYSCALL_DEFINE2(memfd_create,
 		const char __user *, uname,
 		unsigned int, flags)
 {
-	struct file *file;
-	int fd, error;
-	char *name;
+	char *name __free(kfree) = NULL;
+	unsigned int fd_flags;
+	int error;
 
 	error = sanitize_flags(&flags);
 	if (error < 0)
@@ -482,25 +482,11 @@ SYSCALL_DEFINE2(memfd_create,
 	if (IS_ERR(name))
 		return PTR_ERR(name);
 
-	fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
-	if (fd < 0) {
-		error = fd;
-		goto err_free_name;
-	}
-
-	file = alloc_file(name, flags);
-	if (IS_ERR(file)) {
-		error = PTR_ERR(file);
-		goto err_free_fd;
-	}
-
-	fd_install(fd, file);
-	kfree(name);
-	return fd;
+	fd_flags = (flags & MFD_CLOEXEC) ? O_CLOEXEC : 0;
+	FD_PREPARE(fdf, fd_flags, alloc_file(name, flags));
+	error = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (error)
+		return error;
 
-err_free_fd:
-	put_unused_fd(fd);
-err_free_name:
-	kfree(name);
-	return error;
+	return fd_publish(fdf);
 }

-- 
2.47.3

[PATCH RFC v3 26/47] secretmem: convert memfd_secret() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 mm/secretmem.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..b3cd9a33f68e 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -224,8 +224,7 @@ static struct file *secretmem_file_create(unsigned long flags)
 
 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
 {
-	struct file *file;
-	int fd, err;
+	int err;
 
 	/* make sure local flags do not confict with global fcntl.h */
 	BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
@@ -238,22 +237,12 @@ SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
 	if (atomic_read(&secretmem_users) < 0)
 		return -ENFILE;
 
-	fd = get_unused_fd_flags(flags & O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	file = secretmem_file_create(flags);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto err_put_fd;
-	}
-
-	fd_install(fd, file);
-	return fd;
+	FD_PREPARE(fdf, flags & O_CLOEXEC, secretmem_file_create(flags));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
 
-err_put_fd:
-	put_unused_fd(fd);
-	return err;
+	return fd_publish(fdf);
 }
 
 static int secretmem_init_fs_context(struct fs_context *fc)

-- 
2.47.3

[PATCH RFC v3 27/47] net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/handshake/netlink.c | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c
index 7e46d130dce2..db4f35c31bc1 100644
--- a/net/handshake/netlink.c
+++ b/net/handshake/netlink.c
@@ -93,7 +93,7 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
 	struct handshake_net *hn = handshake_pernet(net);
 	struct handshake_req *req = NULL;
 	struct socket *sock;
-	int class, fd, err;
+	int class, err;
 
 	err = -EOPNOTSUPP;
 	if (!hn)
@@ -106,26 +106,22 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
 
 	err = -EAGAIN;
 	req = handshake_req_next(hn, class);
-	if (!req)
-		goto out_status;
-
-	sock = req->hr_sk->sk_socket;
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0) {
-		err = fd;
-		goto out_complete;
-	}
+	if (req) {
+		sock = req->hr_sk->sk_socket;
 
-	err = req->hr_proto->hp_accept(req, info, fd);
-	if (err) {
-		put_unused_fd(fd);
-		goto out_complete;
-	}
+		FD_PREPARE(fdf, O_CLOEXEC, sock->file);
+		err = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (err)
+			goto out_complete;
 
-	fd_install(fd, get_file(sock->file));
+		get_file(sock->file); /* FD_PREPARE() consumes a reference. */
+		err = req->hr_proto->hp_accept(req, info, fd_prepare_fd(fdf));
+		if (err)
+			goto out_complete; /* Automatic cleanup handles fput */
 
-	trace_handshake_cmd_accept(net, req, req->hr_sk, fd);
-	return 0;
+		trace_handshake_cmd_accept(net, req, req->hr_sk, fd_prepare_fd(fdf));
+		return fd_publish(fdf);
+	}
 
 out_complete:
 	handshake_complete(req, -EIO, NULL);

-- 
2.47.3

[PATCH RFC v3 28/47] net/kcm: convert kcm_ioctl() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/kcm/kcmsock.c | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index b4f01cb07561..dace6fada46d 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1560,25 +1560,17 @@ static int kcm_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 	}
 	case SIOCKCMCLONE: {
 		struct kcm_clone info;
-		struct file *file;
 
-		info.fd = get_unused_fd_flags(0);
-		if (unlikely(info.fd < 0))
-			return info.fd;
+		FD_PREPARE(fdf, 0, kcm_clone(sock));
+		err = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (err)
+			return err;
 
-		file = kcm_clone(sock);
-		if (IS_ERR(file)) {
-			put_unused_fd(info.fd);
-			return PTR_ERR(file);
-		}
-		if (copy_to_user((void __user *)arg, &info,
-				 sizeof(info))) {
-			put_unused_fd(info.fd);
-			fput(file);
+		info.fd = fd_prepare_fd(fdf);
+		if (copy_to_user((void __user *)arg, &info, sizeof(info)))
 			return -EFAULT;
-		}
-		fd_install(info.fd, file);
-		err = 0;
+
+		err = fd_publish(fdf);
 		break;
 	}
 	default:

-- 
2.47.3

[PATCH RFC v3 29/47] net/sctp: convert sctp_getsockopt_peeloff_common() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/sctp/socket.c | 89 ++++++++++++++++---------------------------------------
 1 file changed, 25 insertions(+), 64 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ed8293a34240..03f0317c5c38 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5664,47 +5664,46 @@ static int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id,
 	return err;
 }
 
-static int sctp_getsockopt_peeloff_common(struct sock *sk, sctp_peeloff_arg_t *peeloff,
-					  struct file **newfile, unsigned flags)
+static int sctp_getsockopt_peeloff_common(struct sock *sk,
+					  sctp_peeloff_arg_t *peeloff, int len,
+					  char __user *optval,
+					  int __user *optlen, unsigned flags)
 {
 	struct socket *newsock;
 	int retval;
 
 	retval = sctp_do_peeloff(sk, peeloff->associd, &newsock);
 	if (retval < 0)
-		goto out;
+		return retval;
 
-	/* Map the socket to an unused fd that can be returned to the user.  */
-	retval = get_unused_fd_flags(flags & SOCK_CLOEXEC);
-	if (retval < 0) {
+	FD_PREPARE(fdf, flags & SOCK_CLOEXEC, sock_alloc_file(newsock, 0, NULL));
+	retval = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (retval) {
 		sock_release(newsock);
-		goto out;
-	}
-
-	*newfile = sock_alloc_file(newsock, 0, NULL);
-	if (IS_ERR(*newfile)) {
-		put_unused_fd(retval);
-		retval = PTR_ERR(*newfile);
-		*newfile = NULL;
 		return retval;
 	}
 
 	pr_debug("%s: sk:%p, newsk:%p, sd:%d\n", __func__, sk, newsock->sk,
-		 retval);
-
-	peeloff->sd = retval;
+		 fd_prepare_fd(fdf));
 
 	if (flags & SOCK_NONBLOCK)
-		(*newfile)->f_flags |= O_NONBLOCK;
-out:
-	return retval;
+		fd_prepare_file(fdf)->f_flags |= O_NONBLOCK;
+
+	/* Return the fd mapped to the new socket.  */
+	if (put_user(len, optlen))
+		return -EFAULT;
+
+	if (copy_to_user(optval, &peeloff, len))
+		return -EFAULT;
+
+	peeloff->sd = fd_prepare_fd(fdf);
+	return fd_publish(fdf);
 }
 
-static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval, int __user *optlen)
+static int sctp_getsockopt_peeloff(struct sock *sk, int len,
+				   char __user *optval, int __user *optlen)
 {
 	sctp_peeloff_arg_t peeloff;
-	struct file *newfile = NULL;
-	int retval = 0;
 
 	if (len < sizeof(sctp_peeloff_arg_t))
 		return -EINVAL;
@@ -5712,33 +5711,13 @@ static int sctp_getsockopt_peeloff(struct sock *sk, int len, char __user *optval
 	if (copy_from_user(&peeloff, optval, len))
 		return -EFAULT;
 
-	retval = sctp_getsockopt_peeloff_common(sk, &peeloff, &newfile, 0);
-	if (retval < 0)
-		goto out;
-
-	/* Return the fd mapped to the new socket.  */
-	if (put_user(len, optlen)) {
-		fput(newfile);
-		put_unused_fd(retval);
-		return -EFAULT;
-	}
-
-	if (copy_to_user(optval, &peeloff, len)) {
-		fput(newfile);
-		put_unused_fd(retval);
-		return -EFAULT;
-	}
-	fd_install(retval, newfile);
-out:
-	return retval;
+	return sctp_getsockopt_peeloff_common(sk, &peeloff, len, optval, optlen, 0);
 }
 
 static int sctp_getsockopt_peeloff_flags(struct sock *sk, int len,
 					 char __user *optval, int __user *optlen)
 {
 	sctp_peeloff_flags_arg_t peeloff;
-	struct file *newfile = NULL;
-	int retval = 0;
 
 	if (len < sizeof(sctp_peeloff_flags_arg_t))
 		return -EINVAL;
@@ -5746,26 +5725,8 @@ static int sctp_getsockopt_peeloff_flags(struct sock *sk, int len,
 	if (copy_from_user(&peeloff, optval, len))
 		return -EFAULT;
 
-	retval = sctp_getsockopt_peeloff_common(sk, &peeloff.p_arg,
-						&newfile, peeloff.flags);
-	if (retval < 0)
-		goto out;
-
-	/* Return the fd mapped to the new socket.  */
-	if (put_user(len, optlen)) {
-		fput(newfile);
-		put_unused_fd(retval);
-		return -EFAULT;
-	}
-
-	if (copy_to_user(optval, &peeloff, len)) {
-		fput(newfile);
-		put_unused_fd(retval);
-		return -EFAULT;
-	}
-	fd_install(retval, newfile);
-out:
-	return retval;
+	return sctp_getsockopt_peeloff_common(sk, &peeloff.p_arg, len, optval,
+					      optlen, peeloff.flags);
 }
 
 /* 7.1.13 Peer Address Parameters (SCTP_PEER_ADDR_PARAMS)

-- 
2.47.3

[PATCH RFC v3 30/47] net/socket: convert sock_map_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/socket.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index e8892b218708..af72b10ffe49 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -503,21 +503,16 @@ EXPORT_SYMBOL(sock_alloc_file);
 
 static int sock_map_fd(struct socket *sock, int flags)
 {
-	struct file *newfile;
-	int fd = get_unused_fd_flags(flags);
-	if (unlikely(fd < 0)) {
-		sock_release(sock);
-		return fd;
-	}
+	int err;
 
-	newfile = sock_alloc_file(sock, flags, NULL);
-	if (!IS_ERR(newfile)) {
-		fd_install(fd, newfile);
-		return fd;
+	FD_PREPARE(fdf, flags, sock_alloc_file(sock, flags, NULL));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err) {
+		sock_release(sock);
+		return err;
 	}
 
-	put_unused_fd(fd);
-	return PTR_ERR(newfile);
+	return fd_publish(fdf);
 }
 
 /**

-- 
2.47.3

[PATCH RFC v3 31/47] net/socket: convert __sys_accept4_file() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 net/socket.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/net/socket.c b/net/socket.c
index af72b10ffe49..13617083f95f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2007,8 +2007,7 @@ static int __sys_accept4_file(struct file *file, struct sockaddr __user *upeer_s
 			      int __user *upeer_addrlen, int flags)
 {
 	struct proto_accept_arg arg = { };
-	struct file *newfile;
-	int newfd;
+	int err;
 
 	if (flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
 		return -EINVAL;
@@ -2016,18 +2015,12 @@ static int __sys_accept4_file(struct file *file, struct sockaddr __user *upeer_s
 	if (SOCK_NONBLOCK != O_NONBLOCK && (flags & SOCK_NONBLOCK))
 		flags = (flags & ~SOCK_NONBLOCK) | O_NONBLOCK;
 
-	newfd = get_unused_fd_flags(flags);
-	if (unlikely(newfd < 0))
-		return newfd;
+	FD_PREPARE(fdf, flags, do_accept(file, &arg, upeer_sockaddr, upeer_addrlen, flags));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
+		return err;
 
-	newfile = do_accept(file, &arg, upeer_sockaddr, upeer_addrlen,
-			    flags);
-	if (IS_ERR(newfile)) {
-		put_unused_fd(newfd);
-		return PTR_ERR(newfile);
-	}
-	fd_install(newfd, newfile);
-	return newfd;
+	return fd_publish(fdf);
 }
 
 /*

-- 
2.47.3

[PATCH RFC v3 32/47] spufs: convert spufs_context_open() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 arch/powerpc/platforms/cell/spufs/inode.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 7ec60290abe6..413076bc7e3f 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -268,21 +268,13 @@ spufs_mkdir(struct inode *dir, struct dentry *dentry, unsigned int flags,
 static int spufs_context_open(const struct path *path)
 {
 	int ret;
-	struct file *filp;
 
-	ret = get_unused_fd_flags(0);
-	if (ret < 0)
+	FD_PREPARE(fdf, 0, dentry_open(path, O_RDONLY, current_cred()));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
 		return ret;
-
-	filp = dentry_open(path, O_RDONLY, current_cred());
-	if (IS_ERR(filp)) {
-		put_unused_fd(ret);
-		return PTR_ERR(filp);
-	}
-
-	filp->f_op = &spufs_context_fops;
-	fd_install(ret, filp);
-	return ret;
+	fd_prepare_file(fdf)->f_op = &spufs_context_fops;
+	return fd_publish(fdf);
 }
 
 static struct spu_context *

-- 
2.47.3

[PATCH RFC v3 33/47] papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE()

[Christian Brauner]

Fixes a UAF for src_info as well.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 arch/powerpc/platforms/pseries/papr-hvpipe.c | 37 +++++++---------------------
 1 file changed, 9 insertions(+), 28 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
index 21a2f447c43f..e752f3404af6 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
@@ -479,10 +479,8 @@ static const struct file_operations papr_hvpipe_handle_ops = {
 
 static int papr_hvpipe_dev_create_handle(u32 srcID)
 {
-	struct hvpipe_source_info *src_info;
-	struct file *file;
+	struct hvpipe_source_info *src_info __free(kfree) = NULL;
 	long err;
-	int fd;
 
 	spin_lock(&hvpipe_src_list_lock);
 	/*
@@ -506,20 +504,14 @@ static int papr_hvpipe_dev_create_handle(u32 srcID)
 	src_info->tsk = current;
 	init_waitqueue_head(&src_info->recv_wqh);
 
-	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
-	if (fd < 0) {
-		err = fd;
+	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
+		   anon_inode_getfile("[papr-hvpipe]", &papr_hvpipe_handle_ops,
+				      (void *)src_info, O_RDWR));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err)
 		goto free_buf;
-	}
-
-	file = anon_inode_getfile("[papr-hvpipe]",
-			&papr_hvpipe_handle_ops, (void *)src_info,
-			O_RDWR);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto free_fd;
-	}
 
+	retain_and_null_ptr(src_info);
 	spin_lock(&hvpipe_src_list_lock);
 	/*
 	 * If two processes are executing ioctl() for the same
@@ -528,22 +520,11 @@ static int papr_hvpipe_dev_create_handle(u32 srcID)
 	 */
 	if (hvpipe_find_source(srcID)) {
 		spin_unlock(&hvpipe_src_list_lock);
-		err = -EALREADY;
-		goto free_file;
+		return -EALREADY;
 	}
 	list_add(&src_info->list, &hvpipe_src_list);
 	spin_unlock(&hvpipe_src_list_lock);
-
-	fd_install(fd, file);
-	return fd;
-
-free_file:
-	fput(file);
-free_fd:
-	put_unused_fd(fd);
-free_buf:
-	kfree(src_info);
-	return err;
+	return fd_publish(fdf);
 }
 
 /*

-- 
2.47.3

[PATCH RFC v3 34/47] spufs: convert spufs_gang_open() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 arch/powerpc/platforms/cell/spufs/inode.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/inode.c b/arch/powerpc/platforms/cell/spufs/inode.c
index 413076bc7e3f..1ce66b8ffed9 100644
--- a/arch/powerpc/platforms/cell/spufs/inode.c
+++ b/arch/powerpc/platforms/cell/spufs/inode.c
@@ -501,25 +501,17 @@ static const struct file_operations spufs_gang_fops = {
 static int spufs_gang_open(const struct path *path)
 {
 	int ret;
-	struct file *filp;
-
-	ret = get_unused_fd_flags(0);
-	if (ret < 0)
-		return ret;
 
 	/*
 	 * get references for dget and mntget, will be released
 	 * in error path of *_open().
 	 */
-	filp = dentry_open(path, O_RDONLY, current_cred());
-	if (IS_ERR(filp)) {
-		put_unused_fd(ret);
-		return PTR_ERR(filp);
-	}
-
-	filp->f_op = &spufs_gang_fops;
-	fd_install(ret, filp);
-	return ret;
+	FD_PREPARE(fdf, 0, dentry_open(path, O_RDONLY, current_cred()));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
+	fd_prepare_file(fdf)->f_op = &spufs_gang_fops;
+	return fd_publish(fdf);
 }
 
 static int spufs_create_gang(struct inode *inode,

-- 
2.47.3

[PATCH RFC v3 35/47] pseries: convert papr_platform_dump_create_handle() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 .../powerpc/platforms/pseries/papr-platform-dump.c | 39 ++++++++--------------
 1 file changed, 13 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-platform-dump.c b/arch/powerpc/platforms/pseries/papr-platform-dump.c
index f8d55eccdb6b..df9e837f2bd6 100644
--- a/arch/powerpc/platforms/pseries/papr-platform-dump.c
+++ b/arch/powerpc/platforms/pseries/papr-platform-dump.c
@@ -301,11 +301,9 @@ static const struct file_operations papr_platform_dump_handle_ops = {
  */
 static long papr_platform_dump_create_handle(u64 dump_tag)
 {
-	struct ibm_platform_dump_params *params;
+	struct ibm_platform_dump_params *params, *tmp;
 	u64 param_dump_tag;
-	struct file *file;
-	long err;
-	int fd;
+	int err;
 
 	/*
 	 * Return failure if the user space is already opened FD for
@@ -334,34 +332,23 @@ static long papr_platform_dump_create_handle(u64 dump_tag)
 	params->dump_tag_lo = (u32)(dump_tag & 0x00000000ffffffffULL);
 	params->status = RTAS_IBM_PLATFORM_DUMP_START;
 
-	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
-	if (fd < 0) {
-		err = fd;
-		goto free_area;
-	}
-
-	file = anon_inode_getfile_fmode("[papr-platform-dump]",
-				&papr_platform_dump_handle_ops,
-				(void *)params, O_RDONLY,
-				FMODE_LSEEK | FMODE_PREAD);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto put_fd;
+	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
+		   anon_inode_getfile_fmode("[papr-platform-dump]",
+					    &papr_platform_dump_handle_ops,
+					    (void *)params, O_RDONLY,
+					    FMODE_LSEEK | FMODE_PREAD));
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err) {
+		rtas_work_area_free(params->work_area);
+		kfree(params);
+		return err
 	}
 
-	fd_install(fd, file);
-
 	list_add(&params->list, &platform_dump_list);
 
 	pr_info("%s (%d) initiated platform dump for dump tag %llu\n",
 		current->comm, current->pid, dump_tag);
-	return fd;
-put_fd:
-	put_unused_fd(fd);
-free_area:
-	rtas_work_area_free(params->work_area);
-	kfree(params);
-	return err;
+	return fd_publish(fdf);
 }
 
 /*

-- 
2.47.3

[PATCH RFC v3 36/47] pseries: port papr_rtas_setup_file_interface() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 arch/powerpc/platforms/pseries/papr-rtas-common.c | 32 +++++++----------------
 1 file changed, 9 insertions(+), 23 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-rtas-common.c b/arch/powerpc/platforms/pseries/papr-rtas-common.c
index 33c606e3378a..ebe628c69d46 100644
--- a/arch/powerpc/platforms/pseries/papr-rtas-common.c
+++ b/arch/powerpc/platforms/pseries/papr-rtas-common.c
@@ -205,35 +205,21 @@ long papr_rtas_setup_file_interface(struct papr_rtas_sequence *seq,
 				char *name)
 {
 	const struct papr_rtas_blob *blob;
-	struct file *file;
-	long ret;
-	int fd;
+	int ret;
 
 	blob = papr_rtas_retrieve(seq);
 	if (IS_ERR(blob))
 		return PTR_ERR(blob);
 
-	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
-	if (fd < 0) {
-		ret = fd;
-		goto free_blob;
-	}
-
-	file = anon_inode_getfile_fmode(name, fops, (void *)blob,
-			O_RDONLY, FMODE_LSEEK | FMODE_PREAD);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto put_fd;
+	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
+		   anon_inode_getfile_fmode(name, fops, (void *)blob, O_RDONLY,
+					    FMODE_LSEEK | FMODE_PREAD));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret) {
+		papr_rtas_blob_free(blob);
+		return ret;
 	}
-
-	fd_install(fd, file);
-	return fd;
-
-put_fd:
-	put_unused_fd(fd);
-free_blob:
-	papr_rtas_blob_free(blob);
-	return ret;
+	return fd_publish(fdf);
 }
 
 /*

-- 
2.47.3

[PATCH RFC v3 37/47] dma: port sw_sync_ioctl_create_fence() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/dma-buf/sw_sync.c | 42 +++++++++++++++---------------------------
 1 file changed, 15 insertions(+), 27 deletions(-)

diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index 3c20f1d31cf5..7ff0d0e7dbc7 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -343,47 +343,35 @@ static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
 static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 				       unsigned long arg)
 {
-	int fd = get_unused_fd_flags(O_CLOEXEC);
-	int err;
 	struct sync_pt *pt;
 	struct sync_file *sync_file;
 	struct sw_sync_create_fence_data data;
+	int err;
 
-	if (fd < 0)
-		return fd;
-
-	if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
-		err = -EFAULT;
-		goto err;
-	}
+	if (copy_from_user(&data, (void __user *)arg, sizeof(data)))
+		return -EFAULT;
 
 	pt = sync_pt_create(obj, data.value);
-	if (!pt) {
-		err = -ENOMEM;
-		goto err;
-	}
+	if (!pt)
+		return -ENOMEM;
 
 	sync_file = sync_file_create(&pt->base);
 	dma_fence_put(&pt->base);
-	if (!sync_file) {
-		err = -ENOMEM;
-		goto err;
-	}
+	if (!sync_file)
+		return -ENOMEM;
 
-	data.fence = fd;
-	if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
+	FD_PREPARE(fdf, O_CLOEXEC, sync_file->file);
+	err = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (err) {
 		fput(sync_file->file);
-		err = -EFAULT;
-		goto err;
+		return err;
 	}
 
-	fd_install(fd, sync_file->file);
-
-	return 0;
+	data.fence = fd_prepare_fd(fdf);
+	if (copy_to_user((void __user *)arg, &data, sizeof(data)))
+		return -EFAULT;
 
-err:
-	put_unused_fd(fd);
-	return err;
+	return fd_publish(fdf);
 }
 
 static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)

-- 
2.47.3

[PATCH RFC v3 38/47] gpio: convert linehandle_create() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/gpio/gpiolib-cdev.c | 61 ++++++++++++++++++++-------------------------
 1 file changed, 27 insertions(+), 34 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 175836467f21..195bee9018fb 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -298,12 +298,35 @@ static const struct file_operations linehandle_fileops = {
 #endif
 };
 
+static int linehandle_fd_create(struct gpio_device *gdev,
+				struct linehandle_state *lh,
+				struct gpiohandle_request *handlereq,
+				void __user *ip)
+{
+	int ret;
+
+	FD_PREPARE(fdf, O_RDONLY | O_CLOEXEC,
+		   anon_inode_getfile("gpio-linehandle", &linehandle_fileops,
+				      lh, O_RDONLY | O_CLOEXEC));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
+
+	handlereq->fd = fd_prepare_fd(fdf);
+	if (copy_to_user(ip, handlereq, sizeof(handlereq)))
+		return -EFAULT;
+
+	dev_dbg(&gdev->dev, "registered chardev handle for %d lines\n", lh->num_descs);
+
+	fd_publish(fdf);
+	return 0;
+}
+
 static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 {
 	struct gpiohandle_request handlereq;
 	struct linehandle_state *lh;
-	struct file *file;
-	int fd, i, ret;
+	int i, ret;
 	u32 lflags;
 
 	if (copy_from_user(&handlereq, ip, sizeof(handlereq)))
@@ -377,41 +400,11 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 			offset);
 	}
 
-	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
-	if (fd < 0) {
-		ret = fd;
+	ret = linehandle_fd_create(gdev, lh, &handlereq, ip);
+	if (ret)
 		goto out_free_lh;
-	}
-
-	file = anon_inode_getfile("gpio-linehandle",
-				  &linehandle_fileops,
-				  lh,
-				  O_RDONLY | O_CLOEXEC);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto out_put_unused_fd;
-	}
-
-	handlereq.fd = fd;
-	if (copy_to_user(ip, &handlereq, sizeof(handlereq))) {
-		/*
-		 * fput() will trigger the release() callback, so do not go onto
-		 * the regular error cleanup path here.
-		 */
-		fput(file);
-		put_unused_fd(fd);
-		return -EFAULT;
-	}
-
-	fd_install(fd, file);
-
-	dev_dbg(&gdev->dev, "registered chardev handle for %d lines\n",
-		lh->num_descs);
-
 	return 0;
 
-out_put_unused_fd:
-	put_unused_fd(fd);
 out_free_lh:
 	linehandle_free(lh);
 	return ret;

-- 
2.47.3

[PATCH RFC v3 39/47] hv: convert mshv_ioctl_create_partition() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/hv/mshv_root_main.c | 30 ++++++++----------------------
 1 file changed, 8 insertions(+), 22 deletions(-)

diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
index e3b2bd417c46..575c23560bb2 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -1938,30 +1938,16 @@ mshv_ioctl_create_partition(void __user *user_arg, struct device *module_dev)
 		goto delete_partition;
 
 	ret = mshv_init_async_handler(partition);
-	if (ret)
-		goto remove_partition;
-
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0) {
-		ret = fd;
-		goto remove_partition;
-	}
-
-	file = anon_inode_getfile("mshv_partition", &mshv_partition_fops,
-				  partition, O_RDWR);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto put_fd;
+	if (!ret) {
+		FD_PREPARE(fdf, O_CLOEXEC,
+			   anon_inode_getfile("mshv_partition",
+					      &mshv_partition_fops, partition, O_RDWR));
+		ret = ACQUIRE_ERR(fd_prepare, &fdf);
+		if (!ret)
+			return fd_publish(fdf);
 	}
-
-	fd_install(fd, file);
-
-	return fd;
-
-put_fd:
-	put_unused_fd(fd);
-remove_partition:
 	remove_partition(partition);
+
 delete_partition:
 	hv_call_delete_partition(partition->pt_id);
 cleanup_irq_srcu:

-- 
2.47.3

[PATCH RFC v3 40/47] media: convert media_request_alloc() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/media/mc/mc-request.c | 33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
index f66f728b1b43..bf039ab7be93 100644
--- a/drivers/media/mc/mc-request.c
+++ b/drivers/media/mc/mc-request.c
@@ -282,8 +282,6 @@ EXPORT_SYMBOL_GPL(media_request_get_by_fd);
 int media_request_alloc(struct media_device *mdev, int *alloc_fd)
 {
 	struct media_request *req;
-	struct file *filp;
-	int fd;
 	int ret;
 
 	/* Either both are NULL or both are non-NULL */
@@ -297,19 +295,6 @@ int media_request_alloc(struct media_device *mdev, int *alloc_fd)
 	if (!req)
 		return -ENOMEM;
 
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0) {
-		ret = fd;
-		goto err_free_req;
-	}
-
-	filp = anon_inode_getfile("request", &request_fops, NULL, O_CLOEXEC);
-	if (IS_ERR(filp)) {
-		ret = PTR_ERR(filp);
-		goto err_put_fd;
-	}
-
-	filp->private_data = req;
 	req->mdev = mdev;
 	req->state = MEDIA_REQUEST_STATE_IDLE;
 	req->num_incomplete_objects = 0;
@@ -320,19 +305,23 @@ int media_request_alloc(struct media_device *mdev, int *alloc_fd)
 	req->updating_count = 0;
 	req->access_count = 0;
 
-	*alloc_fd = fd;
+	FD_PREPARE(fdf, O_CLOEXEC,
+		   anon_inode_getfile("request", &request_fops, NULL,
+				      O_CLOEXEC));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		goto err_free_req;
+
+	fd_prepare_file(fdf)->private_data = req;
+
+	*alloc_fd = fd_publish(fdf);
 
 	snprintf(req->debug_str, sizeof(req->debug_str), "%u:%d",
-		 atomic_inc_return(&mdev->request_id), fd);
+		 atomic_inc_return(&mdev->request_id), *alloc_fd);
 	dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);
 
-	fd_install(fd, filp);
-
 	return 0;
 
-err_put_fd:
-	put_unused_fd(fd);
-
 err_free_req:
 	if (mdev->ops->req_free)
 		mdev->ops->req_free(req);

-- 
2.47.3

[PATCH RFC v3 41/47] ntsync: convert ntsync_obj_get_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/misc/ntsync.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/misc/ntsync.c b/drivers/misc/ntsync.c
index 999026a1ae04..b7db1628cf26 100644
--- a/drivers/misc/ntsync.c
+++ b/drivers/misc/ntsync.c
@@ -721,21 +721,15 @@ static struct ntsync_obj *ntsync_alloc_obj(struct ntsync_device *dev,
 
 static int ntsync_obj_get_fd(struct ntsync_obj *obj)
 {
-	struct file *file;
-	int fd;
-
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-	file = anon_inode_getfile("ntsync", &ntsync_obj_fops, obj, O_RDWR);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		return PTR_ERR(file);
-	}
-	obj->file = file;
-	fd_install(fd, file);
+	int ret;
 
-	return fd;
+	FD_PREPARE(fdf, O_CLOEXEC,
+		   anon_inode_getfile("ntsync", &ntsync_obj_fops, obj, O_RDWR));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
+	obj->file = fd_prepare_file(fdf);
+	return fd_publish(fdf);
 }
 
 static int ntsync_create_sem(struct ntsync_device *dev, void __user *argp)

-- 
2.47.3

[PATCH RFC v3 42/47] tty: convert ptm_open_peer() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/tty/pty.c | 34 +++++++++-------------------------
 1 file changed, 9 insertions(+), 25 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 8bb1a01fef2a..f9dd2209cc7b 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -601,42 +601,26 @@ static struct cdev ptmx_cdev;
  */
 int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
 {
-	int fd;
-	struct file *filp;
-	int retval = -EINVAL;
+	int ret;
 	struct path path;
 
 	if (tty->driver != ptm_driver)
 		return -EIO;
 
-	fd = get_unused_fd_flags(flags);
-	if (fd < 0) {
-		retval = fd;
-		goto err;
-	}
-
 	/* Compute the slave's path */
 	path.mnt = devpts_mntget(master, tty->driver_data);
-	if (IS_ERR(path.mnt)) {
-		retval = PTR_ERR(path.mnt);
-		goto err_put;
-	}
+	if (IS_ERR(path.mnt))
+		return PTR_ERR(path.mnt);
 	path.dentry = tty->link->driver_data;
 
-	filp = dentry_open(&path, flags, current_cred());
-	mntput(path.mnt);
-	if (IS_ERR(filp)) {
-		retval = PTR_ERR(filp);
-		goto err_put;
+	FD_PREPARE(fdf, flags, dentry_open(&path, flags, current_cred()));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret) {
+		mntput(path.mnt);
+		return ret;
 	}
 
-	fd_install(fd, filp);
-	return fd;
-
-err_put:
-	put_unused_fd(fd);
-err:
-	return retval;
+	return fd_publish(fdf);
 }
 
 static int pty_unix98_ioctl(struct tty_struct *tty,

-- 
2.47.3

[PATCH RFC v3 43/47] vfio: convert vfio_group_ioctl_get_device_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 drivers/vfio/group.c | 27 ++++++---------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
index c376a6279de0..7f706991b867 100644
--- a/drivers/vfio/group.c
+++ b/drivers/vfio/group.c
@@ -299,9 +299,7 @@ static int vfio_group_ioctl_get_device_fd(struct vfio_group *group,
 					  char __user *arg)
 {
 	struct vfio_device *device;
-	struct file *filep;
 	char *buf;
-	int fdno;
 	int ret;
 
 	buf = strndup_user(arg, PAGE_SIZE);
@@ -313,26 +311,13 @@ static int vfio_group_ioctl_get_device_fd(struct vfio_group *group,
 	if (IS_ERR(device))
 		return PTR_ERR(device);
 
-	fdno = get_unused_fd_flags(O_CLOEXEC);
-	if (fdno < 0) {
-		ret = fdno;
-		goto err_put_device;
-	}
-
-	filep = vfio_device_open_file(device);
-	if (IS_ERR(filep)) {
-		ret = PTR_ERR(filep);
-		goto err_put_fdno;
+	FD_PREPARE(fdf, O_CLOEXEC, vfio_device_open_file(device));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret) {
+		vfio_device_put_registration(device);
+		return ret;
 	}
-
-	fd_install(fdno, filep);
-	return fdno;
-
-err_put_fdno:
-	put_unused_fd(fdno);
-err_put_device:
-	vfio_device_put_registration(device);
-	return ret;
+	return fd_publish(fdf);
 }
 
 static int vfio_group_ioctl_get_status(struct vfio_group *group,

-- 
2.47.3

[PATCH RFC v3 44/47] file: convert replace_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/file.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 28743b742e3c..0613ca112baf 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1357,28 +1357,26 @@ int replace_fd(unsigned fd, struct file *file, unsigned flags)
  */
 int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
 {
-	int new_fd;
 	int error;
 
 	error = security_file_receive(file);
 	if (error)
 		return error;
 
-	new_fd = get_unused_fd_flags(o_flags);
-	if (new_fd < 0)
-		return new_fd;
+	FD_PREPARE(fdf, o_flags, file);
+	error = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (error)
+		return error;
+	get_file(file);
 
 	if (ufd) {
-		error = put_user(new_fd, ufd);
-		if (error) {
-			put_unused_fd(new_fd);
+		error = put_user(fd_prepare_fd(fdf), ufd);
+		if (error)
 			return error;
-		}
 	}
 
-	fd_install(new_fd, get_file(file));
-	__receive_sock(file);
-	return new_fd;
+	__receive_sock(fd_prepare_file(fdf));
+	return fd_publish(fdf);
 }
 EXPORT_SYMBOL_GPL(receive_fd);
 

-- 
2.47.3

[PATCH RFC v3 45/47] io_uring: convert io_create_mock_file() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 io_uring/mock_file.c | 46 +++++++++++++++++-----------------------------
 1 file changed, 17 insertions(+), 29 deletions(-)

diff --git a/io_uring/mock_file.c b/io_uring/mock_file.c
index 45d3735b2708..5200a3ed0735 100644
--- a/io_uring/mock_file.c
+++ b/io_uring/mock_file.c
@@ -211,10 +211,10 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	const struct file_operations *fops = &io_mock_fops;
 	const struct io_uring_sqe *sqe = cmd->sqe;
 	struct io_uring_mock_create mc, __user *uarg;
-	struct io_mock_file *mf = NULL;
-	struct file *file = NULL;
+	struct file *file;
+	struct io_mock_file *mf __free(kfree) = NULL;
 	size_t uarg_size;
-	int fd = -1, ret;
+	int ret;
 
 	/*
 	 * It's a testing only driver that allows exercising edge cases
@@ -246,10 +246,6 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 	if (!mf)
 		return -ENOMEM;
 
-	ret = fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
-	if (fd < 0)
-		goto fail;
-
 	init_waitqueue_head(&mf->poll_wq);
 	mf->size = mc.file_size;
 	mf->rw_delay_ns = mc.rw_delay_ns;
@@ -258,33 +254,25 @@ static int io_create_mock_file(struct io_uring_cmd *cmd, unsigned int issue_flag
 		mf->pollable = true;
 	}
 
-	file = anon_inode_create_getfile("[io_uring_mock]", fops,
-					 mf, O_RDWR | O_CLOEXEC, NULL);
-	if (IS_ERR(file)) {
-		ret = PTR_ERR(file);
-		goto fail;
-	}
+	FD_PREPARE(fdf, O_RDWR | O_CLOEXEC,
+		   anon_inode_create_getfile("[io_uring_mock]", fops, mf,
+					     O_RDWR | O_CLOEXEC, NULL));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
-	file->f_mode |= FMODE_READ | FMODE_CAN_READ |
-			FMODE_WRITE | FMODE_CAN_WRITE |
-			FMODE_LSEEK;
+	file = fd_prepare_file(fdf);
+	file->f_mode |= FMODE_READ | FMODE_CAN_READ | FMODE_WRITE |
+			FMODE_CAN_WRITE | FMODE_LSEEK;
 	if (mc.flags & IORING_MOCK_CREATE_F_SUPPORT_NOWAIT)
 		file->f_mode |= FMODE_NOWAIT;
 
-	mc.out_fd = fd;
-	if (copy_to_user(uarg, &mc, uarg_size)) {
-		fput(file);
-		ret = -EFAULT;
-		goto fail;
-	}
+	mc.out_fd = fd_prepare_fd(fdf);
+	if (copy_to_user(uarg, &mc, uarg_size))
+		return -EFAULT;
 
-	fd_install(fd, file);
-	return 0;
-fail:
-	if (fd >= 0)
-		put_unused_fd(fd);
-	kfree(mf);
-	return ret;
+	retain_and_null_ptr(mf);
+	return fd_publish(fdf);
 }
 
 static int io_probe_mock(struct io_uring_cmd *cmd)

-- 
2.47.3

[PATCH RFC v3 46/47] kvm: convert kvm_arch_supports_gmem_init_shared() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 virt/kvm/guest_memfd.c | 37 +++++++++++++------------------------
 1 file changed, 13 insertions(+), 24 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index fbca8c0972da..ca0135dbefa8 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -493,28 +493,22 @@ bool __weak kvm_arch_supports_gmem_init_shared(struct kvm *kvm)
 static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 {
 	const char *anon_name = "[kvm-gmem]";
-	struct kvm_gmem *gmem;
+	struct kvm_gmem *gmem __free(kfree) = NULL;
 	struct inode *inode;
 	struct file *file;
-	int fd, err;
-
-	fd = get_unused_fd_flags(0);
-	if (fd < 0)
-		return fd;
+	int ret;
 
 	gmem = kzalloc(sizeof(*gmem), GFP_KERNEL);
-	if (!gmem) {
-		err = -ENOMEM;
-		goto err_fd;
-	}
+	if (!gmem)
+		return -ENOMEM;
 
-	file = anon_inode_create_getfile(anon_name, &kvm_gmem_fops, gmem,
-					 O_RDWR, NULL);
-	if (IS_ERR(file)) {
-		err = PTR_ERR(file);
-		goto err_gmem;
-	}
+	FD_PREPARE(fdf, 0, anon_inode_create_getfile(anon_name, &kvm_gmem_fops,
+						     gmem, O_RDWR, NULL));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
+	file = fd_prepare_file(fdf);
 	file->f_flags |= O_LARGEFILE;
 
 	inode = file->f_inode;
@@ -535,14 +529,9 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 	xa_init(&gmem->bindings);
 	list_add(&gmem->entry, &inode->i_mapping->i_private_list);
 
-	fd_install(fd, file);
-	return fd;
-
-err_gmem:
-	kfree(gmem);
-err_fd:
-	put_unused_fd(fd);
-	return err;
+	/* Ownership of gmem transferred to file */
+	retain_and_null_ptr(gmem);
+	return fd_publish(fdf);
 }
 
 int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)

-- 
2.47.3

[PATCH RFC v3 47/47] kvm: convert kvm_vcpu_ioctl_get_stats_fd() to FD_PREPARE()

[Christian Brauner]

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 virt/kvm/kvm_main.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b7a0ae2a7b20..f8c5ed12d42d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4313,27 +4313,21 @@ static const struct file_operations kvm_vcpu_stats_fops = {
 
 static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
 {
-	int fd;
-	struct file *file;
+	int ret;
 	char name[15 + ITOA_MAX_LEN + 1];
 
 	snprintf(name, sizeof(name), "kvm-vcpu-stats:%d", vcpu->vcpu_id);
 
-	fd = get_unused_fd_flags(O_CLOEXEC);
-	if (fd < 0)
-		return fd;
-
-	file = anon_inode_getfile_fmode(name, &kvm_vcpu_stats_fops, vcpu,
-					O_RDONLY, FMODE_PREAD);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		return PTR_ERR(file);
-	}
+	FD_PREPARE(fdf, O_CLOEXEC, anon_inode_getfile_fmode(name,
+							     &kvm_vcpu_stats_fops,
+							     vcpu, O_RDONLY,
+							     FMODE_PREAD));
+	ret = ACQUIRE_ERR(fd_prepare, &fdf);
+	if (ret)
+		return ret;
 
 	kvm_get_kvm(vcpu->kvm);
-	fd_install(fd, file);
-
-	return fd;
+	return fd_publish(fdf);
 }
 
 #ifdef CONFIG_KVM_GENERIC_PRE_FAULT_MEMORY

-- 
2.47.3

Re: [PATCH RFC v3 04/47] fhandle: convert do_handle_open() to FD_PREPARE()

[Linus Torvalds]

On Fri, 21 Nov 2025 at 10:01, Christian Brauner <brauner@kernel.org> wrote:
>
> +       FD_PREPARE(fdf, open_flag, file_open_handle(&path, open_flag));
> +       retval = ACQUIRE_ERR(fd_prepare, &fdf);
> +       if (retval)
> +               return retval;
>
> -       fd_install(fd, file);
> -       return take_fd(fd);
> +       return fd_publish(fdf);

Ok, this looks nicer to me, but can we take it one more step further?

Can we just make that FD_PREPARE() macro ust _contain_ the
ACQUIRE_ERR(fd_prepare) thing too?

I realize that you can't make FD_PREPARE() just return the error code,
because it needs to be a statement (in order to declare the new class
variable). So while I'd have *preferred* to see something like

        retval = FD_PREPARE(fdf, open_flag, open_fn(...));
        if (retval)
                return retval;
        return fd_publish(fdf);

that doesn't work syntactically. Foiled by the pitiful C preprocessor again.

But since absolutely everybody *has* to have that

        retval = ACQUIRE_ERR(fd_prepare, &fdf);
        if (retval)
                ...

sequence immediately after the FD_PREPARE(), and since that really
looks like magic line noise, I feel that it should at least be better
integrated.

It could be done multiple ways, I'm sure, but _one_ way to do it would
be to just add the error variable name as an argument, and write it
all as

        FD_PREPARE(fdf, retval, open_flag, open_fn(...));
        if (retval)
                return retval;

which at least avoids *some* of the line noise.

Another way would be to literally just add the "if ()" thing entirely
into it, and declare a local error variable. That can be done by using
a "for()" as an if-statement, ie the final part of the FD_PREPARE()
macro would be

        for (int FD_ERR = ACQUIRE_ERR(fd_prepare, &_var); FD_ERR; FD_ERR=0)

and then you could write all of this out as

        FD_PREPARE(fdf, retval, open_flag, open_fn(...))
                return FD_ERR;
        return fd_publish(fdf);

which admittedly looks a bit odd, but at least avoids having to know
to write out that ACQUIRE_ERR(fd_prepare..) thing, and generally looks
pretty readable to me.

That last thing is certainly compact and avoids any extra noise, but I
think the FD_PREPARE name might need changing to reflect the fact that
it now acts as a if-statement?

Maybe IF_FD_PREP_ERR() or something like that would make it more
natural to have that error condition as part of it?

Anyway, I think this RFC v3 version you posted is certainly
_acceptable_ in this form already, but I get the feeling that it could
be bikeshedded a *bit* more to be even simpler to use and not have
quite as much boilerplate...

              Linus