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Date: Thu, 28 Oct 2010 17:31:45 -0400
From: Eric Paris <eparis@...hat.com>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: agruen@...e.de, tvrtko.ursulin@...hos.com
Subject: [PATCH 02/20] 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@...hat.com>
---
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 */
--
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