[GFS2] Reduce size of struct gdlm_lock

This patch removes the completion (which is rather large) from struct
gdlm_lock in favour of using the wait_on_bit() functions. We don't need
to add any extra fields to the structure to do this, so we save 32 bytes
(on x86_64) per structure. This adds up to quite a lot when we may
potentially have millions of these lock structures,

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Acked-by: David Teigland <teigland@redhat.com>

3 files changed, 18 insertions, 6 deletions

diff --git a/fs/gfs2/locking/dlm/lock.c b/fs/gfs2/locking/dlm/lock.c
index c305255bfe8a..542a797ac89a 100644
--- a/fs/gfs2/locking/dlm/lock.c
+++ b/fs/gfs2/locking/dlm/lock.c
@@ -174,7 +174,6 @@ static int gdlm_create_lp(struct gdlm_ls *ls, struct lm_lockname *name,
         lp->cur = DLM_LOCK_IV;
         lp->lvb = NULL;
         lp->hold_null = NULL;
-        init_completion(&lp->ast_wait);
         INIT_LIST_HEAD(&lp->clist);
         INIT_LIST_HEAD(&lp->blist);
         INIT_LIST_HEAD(&lp->delay_list);
@@ -399,6 +398,12 @@ static void gdlm_del_lvb(struct gdlm_lock *lp)
         lp->lksb.sb_lvbptr = NULL;
 }
 
+static int gdlm_ast_wait(void *word)
+{
+        schedule();
+        return 0;
+}
+
 /* This can do a synchronous dlm request (requiring a lock_dlm thread to get
    the completion) because gfs won't call hold_lvb() during a callback (from
    the context of a lock_dlm thread). */
@@ -424,10 +429,10 @@ static int hold_null_lock(struct gdlm_lock *lp)
         lpn->lkf = DLM_LKF_VALBLK | DLM_LKF_EXPEDITE;
         set_bit(LFL_NOBAST, &lpn->flags);
         set_bit(LFL_INLOCK, &lpn->flags);
+        set_bit(LFL_AST_WAIT, &lpn->flags);
 
-        init_completion(&lpn->ast_wait);
         gdlm_do_lock(lpn);
-        wait_for_completion(&lpn->ast_wait);
+        wait_on_bit(&lpn->flags, LFL_AST_WAIT, gdlm_ast_wait, TASK_UNINTERRUPTIBLE);
         error = lpn->lksb.sb_status;
         if (error) {
                 printk(KERN_INFO "lock_dlm: hold_null_lock dlm error %d\n",
diff --git a/fs/gfs2/locking/dlm/lock_dlm.h b/fs/gfs2/locking/dlm/lock_dlm.h
index d074c6e6f9bf..24d70f73b651 100644
--- a/fs/gfs2/locking/dlm/lock_dlm.h
+++ b/fs/gfs2/locking/dlm/lock_dlm.h
@@ -101,6 +101,7 @@ enum {
         LFL_NOBAST              = 10,
         LFL_HEADQUE             = 11,
         LFL_UNLOCK_DELETE       = 12,
+        LFL_AST_WAIT            = 13,
 };
 
 struct gdlm_lock {
@@ -117,7 +118,6 @@ struct gdlm_lock {
         unsigned long           flags;          /* lock_dlm flags LFL_ */
 
         int                     bast_mode;      /* protected by async_lock */
-        struct completion       ast_wait;
 
         struct list_head        clist;          /* complete */
         struct list_head        blist;          /* blocking */
diff --git a/fs/gfs2/locking/dlm/thread.c b/fs/gfs2/locking/dlm/thread.c
index 9cf1f168eaf8..1aca51e45092 100644
--- a/fs/gfs2/locking/dlm/thread.c
+++ b/fs/gfs2/locking/dlm/thread.c
@@ -44,6 +44,13 @@ static void process_blocking(struct gdlm_lock *lp, int bast_mode)
         ls->fscb(ls->sdp, cb, &lp->lockname);
 }
 
+static void wake_up_ast(struct gdlm_lock *lp)
+{
+        clear_bit(LFL_AST_WAIT, &lp->flags);
+        smp_mb__after_clear_bit();
+        wake_up_bit(&lp->flags, LFL_AST_WAIT);
+}
+
 static void process_complete(struct gdlm_lock *lp)
 {
         struct gdlm_ls *ls = lp->ls;
@@ -136,7 +143,7 @@ static void process_complete(struct gdlm_lock *lp)
          */
 
         if (test_and_clear_bit(LFL_SYNC_LVB, &lp->flags)) {
-                complete(&lp->ast_wait);
+                wake_up_ast(lp);
                 return;
         }
 
@@ -214,7 +221,7 @@ out:
         if (test_bit(LFL_INLOCK, &lp->flags)) {
                 clear_bit(LFL_NOBLOCK, &lp->flags);
                 lp->cur = lp->req;
-                complete(&lp->ast_wait);
+                wake_up_ast(lp);
                 return;
         }