@@ -8,6 +8,12 @@
#include "../mount.h"
+struct fsnotify_iter_info {
+ struct fsnotify_mark *inode_mark;
+ struct fsnotify_mark *vfsmount_mark;
+ int srcu_idx;
+};
+
/* destroy all events sitting in this groups notification queue */
extern void fsnotify_flush_notify(struct fsnotify_group *group);
@@ -126,6 +126,7 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
/* set to 0 when there a no external references to this group */
atomic_set(&group->refcnt, 1);
atomic_set(&group->num_marks, 0);
+ atomic_set(&group->user_waits, 0);
spin_lock_init(&group->notification_lock);
INIT_LIST_HEAD(&group->notification_list);
@@ -109,6 +109,16 @@ void fsnotify_get_mark(struct fsnotify_mark *mark)
atomic_inc(&mark->refcnt);
}
+/*
+ * Get mark reference when we found the mark via lockless traversal of object
+ * list. Mark can be already removed from the list by now and on its way to be
+ * destroyed once SRCU period ends.
+ */
+static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
+{
+ return atomic_inc_not_zero(&mark->refcnt);
+}
+
static void __fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
{
u32 new_mask = 0;
@@ -244,6 +254,72 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
FSNOTIFY_REAPER_DELAY);
}
+bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
+{
+ struct fsnotify_group *group;
+
+ if (WARN_ON_ONCE(!iter_info->inode_mark && !iter_info->vfsmount_mark))
+ return false;
+
+ if (iter_info->inode_mark)
+ group = iter_info->inode_mark->group;
+ else
+ group = iter_info->vfsmount_mark->group;
+
+ /*
+ * Since acquisition of mark reference is an atomic op as well, we can
+ * be sure this inc is seen before any effect of refcount increment.
+ */
+ atomic_inc(&group->user_waits);
+
+ if (iter_info->inode_mark) {
+ /* This can fail if mark is being removed */
+ if (!fsnotify_get_mark_safe(iter_info->inode_mark))
+ goto out_wait;
+ }
+ if (iter_info->vfsmount_mark) {
+ if (!fsnotify_get_mark_safe(iter_info->vfsmount_mark))
+ goto out_inode;
+ }
+
+ /*
+ * Now that both marks are pinned by refcount in the inode / vfsmount
+ * lists, we can drop SRCU lock, and safely resume the list iteration
+ * once userspace returns.
+ */
+ srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
+
+ return true;
+out_inode:
+ if (iter_info->inode_mark)
+ fsnotify_put_mark(iter_info->inode_mark);
+out_wait:
+ if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
+ wake_up(&group->notification_waitq);
+ return false;
+}
+
+void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
+{
+ struct fsnotify_group *group = NULL;
+
+ iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
+ if (iter_info->inode_mark) {
+ group = iter_info->inode_mark->group;
+ fsnotify_put_mark(iter_info->inode_mark);
+ }
+ if (iter_info->vfsmount_mark) {
+ group = iter_info->vfsmount_mark->group;
+ fsnotify_put_mark(iter_info->vfsmount_mark);
+ }
+ /*
+ * We abuse notification_waitq on group shutdown for waiting for all
+ * marks pinned when waiting for userspace.
+ */
+ if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
+ wake_up(&group->notification_waitq);
+}
+
/*
* Mark mark as detached, remove it from group list. Mark still stays in object
* list until its last reference is dropped. Note that we rely on mark being
@@ -628,6 +704,12 @@ void fsnotify_detach_group_marks(struct fsnotify_group *group)
fsnotify_free_mark(mark);
fsnotify_put_mark(mark);
}
+ /*
+ * Some marks can still be pinned when waiting for response from
+ * userspace. Wait for those now. fsnotify_prepare_user_wait() will
+ * not succeed now so this wait is race-free.
+ */
+ wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
}
/* Destroy all marks attached to inode / vfsmount */
@@ -79,6 +79,7 @@ struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
+struct fsnotify_iter_info;
/*
* Each group much define these ops. The fsnotify infrastructure will call
@@ -162,6 +163,8 @@ struct fsnotify_group {
struct fsnotify_event *overflow_event; /* Event we queue when the
* notification list is too
* full */
+ atomic_t user_waits; /* Number of tasks waiting for user
+ * response */
/* groups can define private fields here or use the void *private */
union {
@@ -367,6 +370,8 @@ extern void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group, un
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_unmount_inodes(struct super_block *sb);
+extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
+extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
/* put here because inotify does some weird stuff when destroying watches */
extern void fsnotify_init_event(struct fsnotify_event *event,