tree 219a7d83e993f6b00148d530587d5227fffda642
parent 08da98e1b2f76cdbacf84b9affaa75960dbce515
author Amir Goldstein <amir73il@gmail.com> 1751985401 +0200
committer Jan Kara <jack@suse.cz> 1753719278 +0200

fsnotify: optimize FMODE_NONOTIFY_PERM for the common cases

The most unlikely watched permission event is FAN_ACCESS_PERM, because
at the time that it was introduced there were no evictable ignore mark,
so subscribing to FAN_ACCESS_PERM would have incured a very high
overhead.

Yet, when we set the fmode to FMODE_NOTIFY_HSM(), we never skip trying
to send FAN_ACCESS_PERM, which is almost always a waste of cycles.

We got to this logic because of bundling FAN_OPEN*_PERM and
FAN_ACCESS_PERM in the same category and because FAN_OPEN_PERM is a
commonly used event.

By open coding fsnotify_open_perm() in fsnotify_open_perm_and_set_mode(),
we no longer need to regard FAN_OPEN*_PERM when calculating fmode.

This leaves the case of having pre-content events and not having any
other permission event in the object masks a more likely case than the
other way around.

Rework the fmode macros and code so that their meaning now refers only
to hooks on an already open file:

- FMODE_NOTIFY_NONE()		skip all events
- FMODE_NOTIFY_ACCESS_PERM()	send all permission events including
  				FAN_ACCESS_PERM
- FMODE_NOTIFY_HSM()		send pre-content permission events

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250708143641.418603-3-amir73il@gmail.com