fsnotify: mount point listeners list and global mask

currently all of the notification systems implemented select which inodes
they care about and receive messages only about those inodes (or the
children of those inodes.)  This patch begins to flesh out fsnotify support
for the concept of listeners that want to hear notification for an inode
accessed below a given monut point.  This patch implements a second list
of fsnotify groups to hold these types of groups and a second global mask
to hold the events of interest for this type of group.

The reason we want a second group list and mask is because the inode based
notification should_send_event support which makes each group look for a mark
on the given inode.  With one nfsmount listener that means that every group would
have to take the inode->i_lock, look for their mark, not find one, and return
for every operation.   By seperating vfsmount from inode listeners only when
there is a inode listener will the inode groups have to look for their
mark and take the inode lock.  vfsmount listeners will have to grab the lock and
look for a mark but there should be fewer of them, and one vfsmount listener
won't cause the i_lock to be grabbed and released for every fsnotify group
on every io operation.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: include vfsmount in should_send_event when appropriate

To ensure that a group will not duplicate events when it receives it based
on the vfsmount and the inode should_send_event test we should distinguish
those two cases.  We pass a vfsmount to this function so groups can make
their own determinations.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: put inode specific fields in an fsnotify_mark in a union

The addition of marks on vfs mounts will be simplified if the inode
specific parts of a mark and the vfsmnt specific parts of a mark are
actually in a union so naming can be easy.  This patch just implements the
inode struct and the union.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: add vfsmount specific fields to the fsnotify_mark_entry union

vfsmount marks need mostly the same data as inode specific fields, but for
consistency and understandability we put that data in a vfsmount specific
struct inside a union with inode specific data.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: add flags to fsnotify_mark_entries

To differentiate between inode and vfsmount (or other future) types of
marks we add a flags field and set the inode bit on inode marks (the only
currently supported type of mark)

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: kill FSNOTIFY_EVENT_FILE

Some fsnotify operations send a struct file.  This is more information than
we technically need.  We instead send a struct path in all cases instead of
sometimes a path and sometimes a file.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: rename fsnotify_mark_entry to just fsnotify_mark

The name is long and it serves no real purpose.  So rename
fsnotify_mark_entry to just fsnotify_mark.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: rename fsnotify_find_mark_entry to fsnotify_find_mark

the _entry portion of fsnotify functions is useless.  Drop it.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: rename mark_entry to just mark

previously I used mark_entry when talking about marks on inodes.  The
_entry is pretty useless.  Just use "mark" instead.

Signed-off-by: Eric Paris <eparis@redhat.com>
inotify: rename mark_entry to just mark

rename anything in inotify that deals with mark_entry to just be mark.  It
makes a lot more sense.

Signed-off-by: Eric Paris <eparis@redhat.com>
dnotify: rename mark_entry to mark

nomenclature change.  Used to call things 'entries' but now we just call
them 'marks.'  Do those changes for dnotify.

Signed-off-by: Eric Paris <eparis@redhat.com>
fsnotify: take inode->i_lock inside fsnotify_find_mark_entry()

All callers to fsnotify_find_mark_entry() except one take and
release inode->i_lock around the call.  Take the lock inside
fsnotify_find_mark_entry() instead.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
vfs: introduce FMODE_NONOTIFY

This is a new f_mode which can only be set by the kernel.  It indicates
that the fd was opened by fanotify and should not cause future fanotify
events.  This is needed to prevent fanotify livelock.  An example of
obvious livelock is from fanotify close events.

Process A closes file1
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
notice a pattern?

The fix is to add the FMODE_NONOTIFY bit to the open filp done by the kernel
for fanotify.  Thus when that file is used it will not generate future
events.

This patch simply defines the bit.

Signed-off-by: Eric Paris <eparis@redhat.com>
fanotify: FMODE_NONOTIFY and __O_SYNC in sparc conflict

sparc used the same value as FMODE_NONOTIFY so change FMODE_NONOTIFY to be
something unique.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
fanotify: fscking all notification system

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>
fanotify:drop notification if they exist in the outgoing queue

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: merge notification events with different masks

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: do not clone on merge unless needed

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>
fanotify: fanotify_init syscall declaration

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>
fanotify: fanotify_init syscall implementation

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>