1 files changed, 76 insertions, 9 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index c5e4a49e3a12..e044019cb3b1 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -875,6 +875,14 @@ static inline void ocfs2_generic_handle_convert_action(struct ocfs2_lock_res *lo
                 lockres_or_flags(lockres, OCFS2_LOCK_NEEDS_REFRESH);
 
         lockres->l_level = lockres->l_requested;
+
+        /*
+         * We set the OCFS2_LOCK_UPCONVERT_FINISHING flag before clearing
+         * the OCFS2_LOCK_BUSY flag to prevent the dc thread from
+         * downconverting the lock before the upconvert has fully completed.
+         */
+        lockres_or_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);
+
         lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
 
         mlog_exit_void();
@@ -907,8 +915,6 @@ static int ocfs2_generic_handle_bast(struct ocfs2_lock_res *lockres,
 
         assert_spin_locked(&lockres->l_lock);
 
-        lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);
-
         if (level > lockres->l_blocking) {
                 /* only schedule a downconvert if we haven't already scheduled
                  * one that goes low enough to satisfy the level we're
@@ -921,6 +927,9 @@ static int ocfs2_generic_handle_bast(struct ocfs2_lock_res *lockres,
                 lockres->l_blocking = level;
         }
 
+        if (needs_downconvert)
+                lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);
+
         mlog_exit(needs_downconvert);
         return needs_downconvert;
 }
@@ -1133,6 +1142,7 @@ static inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
         mlog_entry_void();
         spin_lock_irqsave(&lockres->l_lock, flags);
         lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
+        lockres_clear_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);
         if (convert)
                 lockres->l_action = OCFS2_AST_INVALID;
         else
@@ -1323,13 +1333,13 @@ static int __ocfs2_cluster_lock(struct ocfs2_super *osb,
 again:
         wait = 0;
 
+        spin_lock_irqsave(&lockres->l_lock, flags);
+
         if (catch_signals && signal_pending(current)) {
                 ret = -ERESTARTSYS;
-                goto out;
+                goto unlock;
         }
 
-        spin_lock_irqsave(&lockres->l_lock, flags);
-
         mlog_bug_on_msg(lockres->l_flags & OCFS2_LOCK_FREEING,
                         "Cluster lock called on freeing lockres %s! flags "
                         "0x%lx\n", lockres->l_name, lockres->l_flags);
@@ -1346,6 +1356,25 @@ again:
                 goto unlock;
         }
 
+        if (lockres->l_flags & OCFS2_LOCK_UPCONVERT_FINISHING) {
+                /*
+                 * We've upconverted. If the lock now has a level we can
+                 * work with, we take it. If, however, the lock is not at the
+                 * required level, we go thru the full cycle. One way this could
+                 * happen is if a process requesting an upconvert to PR is
+                 * closely followed by another requesting upconvert to an EX.
+                 * If the process requesting EX lands here, we want it to
+                 * continue attempting to upconvert and let the process
+                 * requesting PR take the lock.
+                 * If multiple processes request upconvert to PR, the first one
+                 * here will take the lock. The others will have to go thru the
+                 * OCFS2_LOCK_BLOCKED check to ensure that there is no pending
+                 * downconvert request.
+                 */
+                if (level <= lockres->l_level)
+                        goto update_holders;
+        }
+
         if (lockres->l_flags & OCFS2_LOCK_BLOCKED &&
             !ocfs2_may_continue_on_blocked_lock(lockres, level)) {
                 /* is the lock is currently blocked on behalf of
@@ -1416,11 +1445,14 @@ again:
                 goto again;
         }
 
+update_holders:
         /* Ok, if we get here then we're good to go. */
         ocfs2_inc_holders(lockres, level);
 
         ret = 0;
 unlock:
+        lockres_clear_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);
+
         spin_unlock_irqrestore(&lockres->l_lock, flags);
 out:
         /*
@@ -3155,7 +3187,7 @@ out:
 /* Mark the lockres as being dropped. It will no longer be
  * queued if blocking, but we still may have to wait on it
  * being dequeued from the downconvert thread before we can consider
- * it safe to drop. 
+ * it safe to drop.
  *
  * You can *not* attempt to call cluster_lock on this lockres anymore. */
 void ocfs2_mark_lockres_freeing(struct ocfs2_lock_res *lockres)
@@ -3352,6 +3384,7 @@ static int ocfs2_unblock_lock(struct ocfs2_super *osb,
         unsigned long flags;
         int blocking;
         int new_level;
+        int level;
         int ret = 0;
         int set_lvb = 0;
         unsigned int gen;
@@ -3360,9 +3393,17 @@ static int ocfs2_unblock_lock(struct ocfs2_super *osb,
 
         spin_lock_irqsave(&lockres->l_lock, flags);
 
-        BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BLOCKED));
-
 recheck:
+        /*
+         * Is it still blocking? If not, we have no more work to do.
+         */
+        if (!(lockres->l_flags & OCFS2_LOCK_BLOCKED)) {
+                BUG_ON(lockres->l_blocking != DLM_LOCK_NL);
+                spin_unlock_irqrestore(&lockres->l_lock, flags);
+                ret = 0;
+                goto leave;
+        }
+
         if (lockres->l_flags & OCFS2_LOCK_BUSY) {
                 /* XXX
                  * This is a *big* race.  The OCFS2_LOCK_PENDING flag
@@ -3401,6 +3442,31 @@ recheck:
                 goto leave;
         }
 
+        /*
+         * This prevents livelocks. OCFS2_LOCK_UPCONVERT_FINISHING flag is
+         * set when the ast is received for an upconvert just before the
+         * OCFS2_LOCK_BUSY flag is cleared. Now if the fs received a bast
+         * on the heels of the ast, we want to delay the downconvert just
+         * enough to allow the up requestor to do its task. Because this
+         * lock is in the blocked queue, the lock will be downconverted
+         * as soon as the requestor is done with the lock.
+         */
+        if (lockres->l_flags & OCFS2_LOCK_UPCONVERT_FINISHING)
+                goto leave_requeue;
+
+        /*
+         * How can we block and yet be at NL?  We were trying to upconvert
+         * from NL and got canceled.  The code comes back here, and now
+         * we notice and clear BLOCKING.
+         */
+        if (lockres->l_level == DLM_LOCK_NL) {
+                BUG_ON(lockres->l_ex_holders || lockres->l_ro_holders);
+                lockres->l_blocking = DLM_LOCK_NL;
+                lockres_clear_flags(lockres, OCFS2_LOCK_BLOCKED);
+                spin_unlock_irqrestore(&lockres->l_lock, flags);
+                goto leave;
+        }
+
         /* if we're blocking an exclusive and we have *any* holders,
          * then requeue. */
         if ((lockres->l_blocking == DLM_LOCK_EX)
@@ -3438,6 +3504,7 @@ recheck:
          * may sleep, so we save off a copy of what we're blocking as
          * it may change while we're not holding the spin lock. */
         blocking = lockres->l_blocking;
+        level = lockres->l_level;
         spin_unlock_irqrestore(&lockres->l_lock, flags);
 
         ctl->unblock_action = lockres->l_ops->downconvert_worker(lockres, blocking);
@@ -3446,7 +3513,7 @@ recheck:
                 goto leave;
 
         spin_lock_irqsave(&lockres->l_lock, flags);
-        if (blocking != lockres->l_blocking) {
+        if ((blocking != lockres->l_blocking) || (level != lockres->l_level)) {
                 /* If this changed underneath us, then we can't drop
                  * it just yet. */
                 goto recheck;