NAME
fanotify_init - initialize an fanotify group
SYNOPSIS
int fanotify_init(unsigned int flags, unsigned int event_f_flags, int priority);
DESCRIPTION
fanotify_init() initializes a new fanotify instance and returns a file
descriptor associated with the new fanotify event queue.
The following values can be OR'd into the flags field:
FAN_NONBLOCK Set the O_NONBLOCK file status flag on the new open file description.
Using this flag saves extra calls to fcntl(2) to achieve the same
result.
FAN_CLOEXEC Set the close-on-exec (FD_CLOEXEC) flag on the new file descriptor.
See the description of the O_CLOEXEC flag in open(2) for reasons why
this may be useful.
The event_f_flags argument is unused and must be set to 0
The priority argument is unused and must be set to 0
RETURN VALUE
On success, this system call return a new file descriptor. On error, -1 is
returned, and errno is set to indicate the error.
ERRORS
EINVAL An invalid value was specified in flags.
EINVAL A non-zero valid was passed in event_f_flags or in priority
ENFILE The system limit on the total number of file descriptors has been reached.
ENOMEM Insufficient kernel memory is available.
CONFORMING TO
These system calls are Linux-specific.
Signed-off-by: Eric Paris <eparis@redhat.com>
This patch defines a new syscall fanotify_init() of the form:
int sys_fanotify_init(unsigned int flags, unsigned int event_f_flags,
unsigned int priority)
This syscall is used to create and fanotify group. This is very similar to
the inotify_init() syscall.
Signed-off-by: Eric Paris <eparis@redhat.com>
Currently if 2 events are going to be merged on the notication queue with
different masks the second event will be cloned and will replace the first
event. However if this notification queue is the only place referencing
the event in question there is no reason not to just update the event in
place. We can tell this if the event->refcnt == 1. Since we hold a
reference for each queue this event is on we know that when refcnt == 1
this is the only queue. The other concern is that it might be about to be
added to a new queue, but this can't be the case since fsnotify holds a
reference on the event until it is finished adding it to queues.
Signed-off-by: Eric Paris <eparis@redhat.com>
Instead of just merging fanotify events if they are exactly the same, merge
notification events with different masks. To do this we have to clone the
old event, update the mask in the new event with the new merged mask, and
put the new event in place of the old event.
Signed-off-by: Eric Paris <eparis@redhat.com>
fanotify listeners get an open file descriptor to the object in question so
the ordering of operations is not as important as in other notification
systems. inotify will drop events if the last event in the event FIFO is
the same as the current event. This patch will drop fanotify events if
they are the same as another event anywhere in the event FIFO.
Signed-off-by: Eric Paris <eparis@redhat.com>
fanotify is a novel file notification system which bases notification on
giving userspace both an event type (open, close, read, write) and an open
file descriptor to the object in question. This should address a number of
races and problems with other notification systems like inotify and dnotify
and should allow the future implementation of blocking or access controlled
notification. These are useful for on access scanners or hierachical storage
management schemes.
This patch just implements the basics of the fsnotify functions.
Signed-off-by: Eric Paris <eparis@redhat.com>
Eric Paris