diff options
| author | Linus Torvalds | 2024-05-09 13:04:24 +0200 |
|---|---|---|
| committer | Christian Brauner | 2024-05-10 08:26:31 +0200 |
| commit | c62b758bae6af16fee94f556091fa74883a96b1e (patch) | |
| tree | 78133c1a8dbb78f59a4afa5aa84b6b78e3a2540e /include | |
| parent | a0fde7ed05ff020c3e7f410d73ce4f3a72b262d6 (diff) | |
fcntl: add F_DUPFD_QUERY fcntl()
Often userspace needs to know whether two file descriptors refer to the
same struct file. For example, systemd uses this to filter out duplicate
file descriptors in it's file descriptor store (cf. [1]) and vulkan uses
it to compare dma-buf fds (cf. [2]).
The only api we provided for this was kcmp() but that's not generally
available or might be disallowed because it is way more powerful (allows
ordering of file pointers, operates on non-current task) etc. So give
userspace a simple way of comparing two file descriptors for sameness
adding a new fcntl() F_DUDFD_QUERY.
Link: https://github.com/systemd/systemd/blob/a4f0e0da3573a10bc5404142be8799418760b1d1/src/basic/fd-util.c#L517 [1]
Link: https://gitlab.freedesktop.org/wlroots/wlroots/-/blob/master/render/vulkan/texture.c#L490 [2]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[brauner: commit message]
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/fcntl.h | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 282e90aeb163..c0bcc185fa48 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -9,6 +9,14 @@ #define F_GETLEASE (F_LINUX_SPECIFIC_BASE + 1) /* + * Request nofications on a directory. + * See below for events that may be notified. + */ +#define F_NOTIFY (F_LINUX_SPECIFIC_BASE + 2) + +#define F_DUPFD_QUERY (F_LINUX_SPECIFIC_BASE + 3) + +/* * Cancel a blocking posix lock; internal use only until we expose an * asynchronous lock api to userspace: */ @@ -18,12 +26,6 @@ #define F_DUPFD_CLOEXEC (F_LINUX_SPECIFIC_BASE + 6) /* - * Request nofications on a directory. - * See below for events that may be notified. - */ -#define F_NOTIFY (F_LINUX_SPECIFIC_BASE+2) - -/* * Set and get of pipe page size array */ #define F_SETPIPE_SZ (F_LINUX_SPECIFIC_BASE + 7) |