This adds the pidfd_prepare() helper which allows the caller to reserve a pidfd number and allocates a new pidfd file that stashes the provided struct pid. This will allow us to remove places that either open code this functionality e.g., during copy_process() or that currently call pidfd_create() but then have to call close_fd() because there are still failure points after pidfd_create() has been called. Other functionality wants to make use of pidfd's as well and they need a pidfd_prepare() internal api as well. I've tested the fanotify and fork changes via LTP which provides coverage for all the affected codepaths. Cc: Jan Kara <jack@suse.cz> Cc: Amir Goldstein <amir73il@gmail.com> Cc: Matthew Bobrowski <repnop@google.com> Cc: linux-kernel@vger.kernel.org To: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org> --- b4-submit-tracking --- # This section is used internally by b4 prep for tracking purposes. { "series": { "revision": 1, "change-id": "20230327-pidfd-file-api-8b28d68cf0a9", "base-branch": "master.v6.3-rc4", "prefixes": [] } }