Messages in this thread Patch in this message | | | Subject | [RFC 8/11] fanotify: ability for userspace to delay responses | From | Eric Paris <> | Date | Fri, 26 Sep 2008 17:19:11 -0400 |
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fanotify: ability for userspace to delay responses
From: Eric Paris <eparis@redhat.com>
Userspace may know that it is behind, may know it is going to take a while to get a good response, or have any number of other reasons to block an access request. FAN_RESTTIMER will reset the timeout for an fanotify access decision response.
Signed-off-by: Eric Paris <eparis@redhat.com> ---
fs/notify/access.c | 33 ++++++++++++++++++++++++++++----- fs/notify/fanotify.h | 2 ++ fs/notify/notification.c | 2 ++ include/linux/fanotify.h | 5 +++-- 4 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/fs/notify/access.c b/fs/notify/access.c index 132ef7b..b4b132b 100644 --- a/fs/notify/access.c +++ b/fs/notify/access.c @@ -56,6 +56,8 @@ int add_event_to_group_access(struct fanotify_group *group, struct fanotify_even int get_response_from_group_access(struct fanotify_group *group, struct fanotify_event *event) { int ret; + +retry: ret = wait_event_interruptible_timeout(group->access_waitq, event->response, msecs_to_jiffies(5000)); @@ -88,13 +90,25 @@ int get_response_from_group_access(struct fanotify_group *group, struct fanotify } /* userspace responded, convert to something usable */ + spin_lock(&event->response_lock); switch (event->response) { case FAN_ALLOW: - return 0; + ret = 0; + break; case FAN_DENY: + ret = -EPERM; + break; + case FAN_RESETTIMER: + event->response = 0; + spin_unlock(&event->response_lock); + goto retry; default: - return -EPERM; + ret = -EPERM; + break; } + spin_unlock(&event->response_lock); + + return ret; } int fanotify_process_access_response(struct fanotify_group *group, unsigned long cookie, unsigned int response) @@ -107,7 +121,7 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long * userspace can send a valid responce or we will clean it up after the * timeout */ - if (response & ~(FAN_ALLOW | FAN_DENY)) + if (response & ~(FAN_ALLOW | FAN_DENY | FAN_RESETTIMER)) return -EINVAL; mutex_lock(&group->access_mutex); @@ -116,11 +130,16 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long continue; event = holder->event; + + /* FAN_RESETTIMER should be left on the list for later.... */ + if (response == FAN_RESETTIMER) + break; + holder->event = NULL; /* as soon as we do this the event.holder might be reused */ list_del_init(&holder->event_list); - if (event != (struct fanotify_event *)holder) + if (event != (struct fanotify_event *)holder) destroy_event_holder(holder); break; } @@ -129,9 +148,13 @@ int fanotify_process_access_response(struct fanotify_group *group, unsigned long if (!event) return -ENOENT; + spin_lock(&event->response_lock); event->response = response; + spin_unlock(&event->response_lock); wake_up(&group->access_waitq); - put_event(event); + + if (response != FAN_RESETTIMER) + put_event(event); return 0; } diff --git a/fs/notify/fanotify.h b/fs/notify/fanotify.h index 38e156e..cb97dbb 100644 --- a/fs/notify/fanotify.h +++ b/fs/notify/fanotify.h @@ -9,6 +9,7 @@ #include <linux/list.h> #include <linux/mutex.h> #include <linux/path.h> +#include <linux/spinlock.h> #include <linux/types.h> #include <linux/wait.h> @@ -74,6 +75,7 @@ struct fanotify_event { atomic_t refcnt; /* how many groups still are using/need to send this event */ /* if waiting for a userspace access answer this is the cookie they will send back */ unsigned long cookie; + spinlock_t response_lock; /* protects response */ unsigned int response; /* userspace answer to question */ }; diff --git a/fs/notify/notification.c b/fs/notify/notification.c index e1a6a24..aa74137 100644 --- a/fs/notify/notification.c +++ b/fs/notify/notification.c @@ -25,6 +25,7 @@ #include <linux/path.h> #include <linux/sched.h> #include <linux/slab.h> +#include <linux/spinlock.h> #include <linux/fanotify.h> #include "fanotify.h" @@ -135,6 +136,7 @@ struct fanotify_event *create_event(struct file *file, unsigned int mask) event->holder.event = NULL; INIT_LIST_HEAD(&event->holder.event_list); atomic_set(&event->refcnt, 1); + spin_lock_init(&event->response_lock); event->path.dentry = file->f_path.dentry; event->path.mnt = file->f_path.mnt; diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h index 5d3e5d0..2a31e53 100644 --- a/include/linux/fanotify.h +++ b/include/linux/fanotify.h @@ -44,9 +44,10 @@ #define FAN_ALL_EVENTS_ACCESS (FAN_OPEN_ACCESS |\ FAN_READ_ACCESS) -/* answers will need to be either allow or deny */ +/* answers will need to be either allow, deny, or reset */ #define FAN_ALLOW 0x00000001 -#define FAN_DENY 0x00000010 +#define FAN_DENY 0x00000002 +#define FAN_RESETTIMER 0x00000004 #ifdef __KERNEL__
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