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Subject[PATCH 03/13] fsnotify: add group priorities
Date
This introduces an ordering to fnotify groups.  It's most interesting because
an HSM would need to run before a typical access notifier. And an access
control system would need to run between the two.

Signed-off-by: Eric Paris <eparis@redhat.com>
---
fs/notify/group.c | 29 ++++++++++++++++++++++-------
include/linux/fsnotify_backend.h | 4 +++-
2 files changed, 25 insertions(+), 8 deletions(-)
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 88d040b..dd1d18d 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -49,8 +49,21 @@ void fsnotify_recalc_global_mask(void)

static void fsnotify_add_group(struct fsnotify_group *group)
{
- list_add_rcu(&group->group_list, &fsnotify_groups);
+ int priority = group->priority;
+ struct fsnotify_group *group_iter;
+
group->evicted = 0;
+ list_for_each_entry(group_iter, &fsnotify_groups, group_list) {
+ /* insert in front of this one? */
+ if (priority < group_iter->priority) {
+ /* I used list_add_tail() to insert in front of group_iter... */
+ list_add_tail_rcu(&group->group_list, &group_iter->group_list);
+ return;
+ }
+ }
+
+ /* apparently we need to be the last entry */
+ list_add_tail_rcu(&group->group_list, &fsnotify_groups);
}

static void fsnotify_get_group(struct fsnotify_group *group)
@@ -101,8 +114,8 @@ void fsnotify_put_group(struct fsnotify_group *group)
fsnotify_destroy_group(group);
}

-static struct fsnotify_group *fsnotify_find_group(unsigned int group_num, __u32 mask,
- const struct fsnotify_ops *ops)
+static struct fsnotify_group *fsnotify_find_group(unsigned int priority, unsigned int group_num,
+ __u32 mask, const struct fsnotify_ops *ops)
{
struct fsnotify_group *group_iter;
struct fsnotify_group *group = NULL;
@@ -110,8 +123,9 @@ static struct fsnotify_group *fsnotify_find_group(unsigned int group_num, __u32
BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));

list_for_each_entry_rcu(group_iter, &fsnotify_groups, group_list) {
- if (group_iter->group_num == group_num) {
+ if (group_iter->priority == priority) {
if ((group_iter->mask == mask) &&
+ (group_iter->group_num == group_num) &&
(group_iter->ops == ops)) {
fsnotify_get_group(group_iter);
group = group_iter;
@@ -131,8 +145,8 @@ static struct fsnotify_group *fsnotify_find_group(unsigned int group_num, __u32
* the allocation and the initialization, but this is only called when notification
* systems make changes, so why make it more complex?
*/
-struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,
- const struct fsnotify_ops *ops)
+struct fsnotify_group *fsnotify_obtain_group(unsigned int priority, unsigned int group_num,
+ __u32 mask, const struct fsnotify_ops *ops)
{
struct fsnotify_group *group, *tgroup;

@@ -142,13 +156,14 @@ struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask,

atomic_set(&group->refcnt, 1);

+ group->priority = priority;
group->group_num = group_num;
group->mask = mask;

group->ops = ops;

mutex_lock(&fsnotify_grp_mutex);
- tgroup = fsnotify_find_group(group_num, mask, ops);
+ tgroup = fsnotify_find_group(priority, group_num, mask, ops);
if (tgroup) {
/* group already exists */
mutex_unlock(&fsnotify_grp_mutex);
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 0523333..a349691 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -76,6 +76,7 @@ struct fsnotify_group {

const struct fsnotify_ops *ops; /* how this group handles things */

+ unsigned int priority; /* order this group should receive msgs. low first */
unsigned int evicted:1; /* has this group been evicted? */

/* groups can define private fields here */
@@ -115,7 +116,8 @@ extern void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)

/* called from fsnotify interfaces, such as fanotify or dnotify */
extern void fsnotify_recalc_global_mask(void);
-extern struct fsnotify_group *fsnotify_obtain_group(unsigned int group_num, __u32 mask, const struct fsnotify_ops *ops);
+extern struct fsnotify_group *fsnotify_obtain_group(unsigned int priority, unsigned int group_num,
+ __u32 mask, const struct fsnotify_ops *ops);
extern void fsnotify_put_group(struct fsnotify_group *group);

extern void fsnotify_get_event(struct fsnotify_event *event);


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