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 #include <net/net_namespace.h>
   8
   9 #include "netns.h"
  10
  11 static DEFINE_SPINLOCK(grace_lock);
  12
  13 /**
  14  * locks_start_grace
  15  * @lm: who this grace period is for
  16  *
  17  * A grace period is a period during which locks should not be given
  18  * out.  Currently grace periods are only enforced by the two lock
  19  * managers (lockd and nfsd), using the locks_in_grace() function to
  20  * check when they are in a grace period.
  21  *
  22  * This function is called to start a grace period.
  23  */
  24 void locks_start_grace(struct net *net, struct lock_manager *lm)
  25 {
  26         struct lockd_net *ln = net_generic(net, lockd_net_id);
  27
  28         spin_lock(&grace_lock);
  29         list_add(&lm->list, &ln->grace_list);
  30         spin_unlock(&grace_lock);
  31 }
  32 EXPORT_SYMBOL_GPL(locks_start_grace);
  33
  34 /**
  35  * locks_end_grace
  36  * @lm: who this grace period is for
  37  *
  38  * Call this function to state that the given lock manager is ready to
  39  * resume regular locking.  The grace period will not end until all lock
  40  * managers that called locks_start_grace() also call locks_end_grace().
  41  * Note that callers count on it being safe to call this more than once,
  42  * and the second call should be a no-op.
  43  */
  44 void locks_end_grace(struct lock_manager *lm)
  45 {
  46         spin_lock(&grace_lock);
  47         list_del_init(&lm->list);
  48         spin_unlock(&grace_lock);
  49 }
  50 EXPORT_SYMBOL_GPL(locks_end_grace);
  51
  52 /**
  53  * locks_in_grace
  54  *
  55  * Lock managers call this function to determine when it is OK for them
  56  * to answer ordinary lock requests, and when they should accept only
  57  * lock reclaims.
  58  */
  59 int locks_in_grace(struct net *net)
  60 {
  61         struct lockd_net *ln = net_generic(net, lockd_net_id);
  62
  63         return !list_empty(&ln->grace_list);
  64 }
  65 EXPORT_SYMBOL_GPL(locks_in_grace);