fs/lockd/grace.c

   1 /*
   2  * Common code for control of lockd and nfsv4 grace periods.
   3  */
   4
   5 #include <linux/module.h>
   6 #include <linux/lockd/bind.h>
   7
   8 static LIST_HEAD(grace_list);
   9 static DEFINE_SPINLOCK(grace_lock);
  10
  11 /**
  12  * locks_start_grace
  13  * @lm: who this grace period is for
  14  *
  15  * A grace period is a period during which locks should not be given
  16  * out.  Currently grace periods are only enforced by the two lock
  17  * managers (lockd and nfsd), using the locks_in_grace() function to
  18  * check when they are in a grace period.
  19  *
  20  * This function is called to start a grace period.
  21  */
  22 void locks_start_grace(struct lock_manager *lm)
  23 {
  24         spin_lock(&grace_lock);
  25         list_add(&lm->list, &grace_list);
  26         spin_unlock(&grace_lock);
  27 }
  28 EXPORT_SYMBOL_GPL(locks_start_grace);
  29
  30 /**
  31  * locks_end_grace
  32  * @lm: who this grace period is for
  33  *
  34  * Call this function to state that the given lock manager is ready to
  35  * resume regular locking.  The grace period will not end until all lock
  36  * managers that called locks_start_grace() also call locks_end_grace().
  37  * Note that callers count on it being safe to call this more than once,
  38  * and the second call should be a no-op.
  39  */
  40 void locks_end_grace(struct lock_manager *lm)
  41 {
  42         spin_lock(&grace_lock);
  43         list_del_init(&lm->list);
  44         spin_unlock(&grace_lock);
  45 }
  46 EXPORT_SYMBOL_GPL(locks_end_grace);
  47
  48 /**
  49  * locks_in_grace
  50  *
  51  * Lock managers call this function to determine when it is OK for them
  52  * to answer ordinary lock requests, and when they should accept only
  53  * lock reclaims.
  54  */
  55 int locks_in_grace(void)
  56 {
  57         return !list_empty(&grace_list);
  58 }
  59 EXPORT_SYMBOL_GPL(locks_in_grace);