dlm: fix locking of lockspace list in dlm_scand

The dlm_scand thread needs to lock the list of lockspaces
when going through it.

Signed-off-by: David Teigland <teigland@redhat.com>

2 files changed, 26 insertions, 2 deletions

diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
index 9e0622aff496..868e4c9ef127 100644
--- a/fs/dlm/dlm_internal.h
+++ b/fs/dlm/dlm_internal.h
@@ -445,6 +445,7 @@ struct dlm_ls {
                                                    the dlm using this ls */
         int                     ls_create_count; /* create/release refcount */
         unsigned long           ls_flags;       /* LSFL_ */
+        unsigned long           ls_scan_time;
         struct kobject          ls_kobj;
 
         struct dlm_rsbtable     *ls_rsbtbl;
diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
index ba672fe0a601..d910501de6d2 100644
--- a/fs/dlm/lockspace.c
+++ b/fs/dlm/lockspace.c
@@ -212,19 +212,41 @@ void dlm_lockspace_exit(void)
         kset_unregister(dlm_kset);
 }
 
+static struct dlm_ls *find_ls_to_scan(void)
+{
+        struct dlm_ls *ls;
+
+        spin_lock(&lslist_lock);
+        list_for_each_entry(ls, &lslist, ls_list) {
+                if (time_after_eq(jiffies, ls->ls_scan_time +
+                                            dlm_config.ci_scan_secs * HZ)) {
+                        spin_unlock(&lslist_lock);
+                        return ls;
+                }
+        }
+        spin_unlock(&lslist_lock);
+        return NULL;
+}
+
 static int dlm_scand(void *data)
 {
         struct dlm_ls *ls;
+        int timeout_jiffies = dlm_config.ci_scan_secs * HZ;
 
         while (!kthread_should_stop()) {
-                list_for_each_entry(ls, &lslist, ls_list) {
+                ls = find_ls_to_scan();
+                if (ls) {
                         if (dlm_lock_recovery_try(ls)) {
+                                ls->ls_scan_time = jiffies;
                                 dlm_scan_rsbs(ls);
                                 dlm_scan_timeout(ls);
                                 dlm_unlock_recovery(ls);
+                        } else {
+                                ls->ls_scan_time += HZ;
                         }
+                } else {
+                        schedule_timeout_interruptible(timeout_jiffies);
                 }
-                schedule_timeout_interruptible(dlm_config.ci_scan_secs * HZ);
         }
         return 0;
 }
@@ -418,6 +440,7 @@ static int new_lockspace(char *name, int namelen, void **lockspace,
         ls->ls_lvblen = lvblen;
         ls->ls_count = 0;
         ls->ls_flags = 0;
+        ls->ls_scan_time = jiffies;
 
         if (flags & DLM_LSFL_TIMEWARN)
                 set_bit(LSFL_TIMEWARN, &ls->ls_flags);