From 6ad2d4e3e97ee4bfde0b45e8dfe37911330fc4aa Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Thu, 28 Oct 2010 17:21:56 -0400 Subject: [PATCH] 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 --- fs/notify/inode_mark.c | 9 +++++++-- fs/notify/vfsmount_mark.c | 6 +++++- include/linux/fsnotify_backend.h | 8 ++++++++ 3 files changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c index 21ed106..4c29fcf 100644 --- a/fs/notify/inode_mark.c +++ b/fs/notify/inode_mark.c @@ -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); diff --git a/fs/notify/vfsmount_mark.c b/fs/notify/vfsmount_mark.c index 56772b5..85eebff 100644 --- a/fs/notify/vfsmount_mark.c +++ b/fs/notify/vfsmount_mark.c @@ -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); diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index e40190d..8253295 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -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 */ -- 2.7.4