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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: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric Paris 2010-10-28 17:21:56 -04:00
parent 9343919c14
commit 6ad2d4e3e9
3 changed files with 20 additions and 3 deletions
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9
fs/notify/inode_mark.c
View File

@ -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);

6
fs/notify/vfsmount_mark.c
View File

@ -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);

8
include/linux/fsnotify_backend.h
View File

@ -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 */