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authorEric Paris <eparis@redhat.com>2009-12-17 21:24:34 -0500
committerEric Paris <eparis@redhat.com>2010-07-28 09:59:01 -0400
commitcb2d429faf2cae62d3c51e28099a181d5fe8c244 (patch)
tree401bc8d85e7228f868775269e6d97c3150f9a3a7
parent4d92604cc90aa18bbbe0f6e23b7a9fdb612836d3 (diff)
fsnotify: add group priorities
This introduces an ordering to fsnotify groups. With purely asynchronous notification based "things" implementing fsnotify (inotify, dnotify) ordering isn't particularly important. But if people want to use fsnotify for the basis of sycronous notification or blocking notification ordering becomes important. eg. A Hierarchical Storage Management listener would need to get its event before an AV scanner could get its event (since the HSM would need to bring the data in for the AV scanner to scan.) Typically asynchronous notification would want to run after the AV scanner made any relevant access decisions so as to not send notification about an event that was denied. Signed-off-by: Eric Paris <eparis@redhat.com>
-rw-r--r--fs/notify/fanotify/fanotify_user.c4
-rw-r--r--fs/notify/group.c40
-rw-r--r--include/linux/fsnotify_backend.h1
3 files changed, 41 insertions, 4 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 9fe760baf69..84d3e2047de 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -463,8 +463,6 @@ SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
if (event_f_flags)
return -EINVAL;
- if (priority)
- return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
@@ -483,6 +481,8 @@ SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
if (IS_ERR(group))
return PTR_ERR(group);
+ group->priority = priority;
+
fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
if (fd < 0)
goto out_put_group;
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 9e9eb406afd..ada913fd4f7 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -89,10 +89,27 @@ void fsnotify_recalc_group_mask(struct fsnotify_group *group)
void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
{
+ struct fsnotify_group *group_iter;
+ unsigned int priority = group->priority;
+
mutex_lock(&fsnotify_grp_mutex);
- if (!group->on_vfsmount_group_list)
+ if (!group->on_vfsmount_group_list) {
+ list_for_each_entry(group_iter, &fsnotify_vfsmount_groups,
+ vfsmount_group_list) {
+ /* insert in front of this one? */
+ if (priority < group_iter->priority) {
+ /* list_add_tail() insert in front of group_iter */
+ list_add_tail_rcu(&group->inode_group_list,
+ &group_iter->inode_group_list);
+ goto out;
+ }
+ }
+
+ /* apparently we need to be the last entry */
list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
+ }
+out:
group->on_vfsmount_group_list = 1;
mutex_unlock(&fsnotify_grp_mutex);
@@ -100,10 +117,27 @@ void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
void fsnotify_add_inode_group(struct fsnotify_group *group)
{
+ struct fsnotify_group *group_iter;
+ unsigned int priority = group->priority;
+
mutex_lock(&fsnotify_grp_mutex);
- if (!group->on_inode_group_list)
+ /* add to global group list, priority 0 first, UINT_MAX last */
+ if (!group->on_inode_group_list) {
+ list_for_each_entry(group_iter, &fsnotify_inode_groups,
+ inode_group_list) {
+ if (priority < group_iter->priority) {
+ /* list_add_tail() insert in front of group_iter */
+ list_add_tail_rcu(&group->inode_group_list,
+ &group_iter->inode_group_list);
+ goto out;
+ }
+ }
+
+ /* apparently we need to be the last entry */
list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
+ }
+out:
group->on_inode_group_list = 1;
mutex_unlock(&fsnotify_grp_mutex);
@@ -226,6 +260,8 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
spin_lock_init(&group->mark_lock);
INIT_LIST_HEAD(&group->marks_list);
+ group->priority = UINT_MAX;
+
group->ops = ops;
return group;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index be4a36ed200..8b2e095e590 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -140,6 +140,7 @@ struct fsnotify_group {
* a group */
struct list_head marks_list; /* all inode marks for this group */
+ unsigned int priority; /* order of this group compared to others */
/* prevents double list_del of group_list. protected by global fsnotify_grp_mutex */
bool on_inode_group_list;
bool on_vfsmount_group_list;