Commit 6ad2d4e3 authored by Eric Paris's avatar Eric Paris
Browse files

fsnotify: implement ordering between notifiers 



fanotify needs to be able to specify that some groups get events before
others.  They use this idea to make sure that a hierarchical storage
manager gets access to files before programs which actually use them.  This
is purely infrastructure.  Everything will have a priority of 0, but the
infrastructure will exist for it to be non-zero.

Signed-off-by: default avatarEric Paris <eparis@redhat.com>
parent 9343919c

fs/notify/inode_mark.c

+7 −2
Original line number Diff line number Diff line
@@ -177,7 +177,8 @@ void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark, 
 * Attach an initialized mark to a given inode.

 * These marks may be used for the fsnotify backend to determine which

 * event types should be delivered to which group and for which inodes.  These

 * marks are ordered according to the group's location in memory.

 * marks are ordered according to priority, highest number first, and then by

 * the group's location in memory.

 */

int fsnotify_add_inode_mark(struct fsnotify_mark *mark,

			    struct fsnotify_group *group, struct inode *inode,
@@ -211,7 +212,11 @@ int fsnotify_add_inode_mark(struct fsnotify_mark *mark, 
			goto out;

		}



		if (mark->group < lmark->group)

		if (mark->group->priority < lmark->group->priority)

			continue;



		if ((mark->group->priority == lmark->group->priority) &&

		    (mark->group < lmark->group))

			continue;



		hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);

fs/notify/vfsmount_mark.c

+5 −1
Original line number Diff line number Diff line
@@ -169,7 +169,11 @@ int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark, 
			goto out;

		}



		if (mark->group < lmark->group)

		if (mark->group->priority < lmark->group->priority)

			continue;



		if ((mark->group->priority == lmark->group->priority) &&

		    (mark->group < lmark->group))

			continue;



		hlist_add_before_rcu(&mark->m.m_list, &lmark->m.m_list);

include/linux/fsnotify_backend.h

+8 −0
Original line number Diff line number Diff line
@@ -129,6 +129,14 @@ struct fsnotify_group { 
	wait_queue_head_t notification_waitq;	/* read() on the notification file blocks on this waitq */

	unsigned int q_len;			/* events on the queue */

	unsigned int max_events;		/* maximum events allowed on the list */

	/*

	 * Valid fsnotify group priorities.  Events are send in order from highest

	 * priority to lowest priority.  We default to the lowest priority.

	 */

	#define FS_PRIO_0	0 /* normal notifiers, no permissions */

	#define FS_PRIO_1	1 /* fanotify content based access control */

	#define FS_PRIO_2	2 /* fanotify pre-content access */

	unsigned int priority;



	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */

	spinlock_t mark_lock;		/* protect marks_list */

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