From: Jeff Layton <jlayton@redhat.com>
Date: Mon, 26 Oct 2009 15:54:16 -0400
Subject: [cifs] protect GlobalOplock_Q with its own spinlock
Message-id: <1256572464-27293-2-git-send-email-jlayton@redhat.com>
Patchwork-id: 21211
O-Subject: [RHEL5.5 PATCH 1/9] BZ#531005: cifs: protect GlobalOplock_Q with its
	own spinlock
Bugzilla: 531005
RH-Acked-by: Steve Dickson <SteveD@redhat.com>
RH-Acked-by: Peter Staubach <staubach@redhat.com>

Right now, the GlobalOplock_Q is protected by the GlobalMid_Lock. That
lock is also used for completely unrelated purposes (mostly for managing
the global mid queue). Give the list its own dedicated spinlock
(cifs_oplock_lock) and rename the list to cifs_oplock_list to
eliminate the camel-case.

Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 68ae5d8..1238996 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1113,19 +1113,19 @@ static int cifs_oplock_thread(void *dummyarg)
 			continue;
 #endif
 
-		spin_lock(&GlobalMid_Lock);
-		if (list_empty(&GlobalOplock_Q)) {
-			spin_unlock(&GlobalMid_Lock);
+		spin_lock(&cifs_oplock_lock);
+		if (list_empty(&cifs_oplock_list)) {
+			spin_unlock(&cifs_oplock_lock);
 			set_current_state(TASK_INTERRUPTIBLE);
 			schedule_timeout(39*HZ);
 		} else {
-			oplock_item = list_entry(GlobalOplock_Q.next,
+			oplock_item = list_entry(cifs_oplock_list.next,
 						struct oplock_q_entry, qhead);
 			cFYI(1, ("found oplock item to write out"));
 			pTcon = oplock_item->tcon;
 			inode = oplock_item->pinode;
 			netfid = oplock_item->netfid;
-			spin_unlock(&GlobalMid_Lock);
+			spin_unlock(&cifs_oplock_lock);
 			DeleteOplockQEntry(oplock_item);
 			/* can not grab inode sem here since it would
 				deadlock when oplock received on delete
@@ -1176,7 +1176,7 @@ init_cifs(void)
 	int rc = 0;
 	cifs_proc_init();
 	INIT_LIST_HEAD(&cifs_tcp_ses_list);
-	INIT_LIST_HEAD(&GlobalOplock_Q);
+	INIT_LIST_HEAD(&cifs_oplock_list);
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	INIT_LIST_HEAD(&GlobalDnotifyReqList);
 	INIT_LIST_HEAD(&GlobalDnotifyRsp_Q);
@@ -1205,6 +1205,7 @@ init_cifs(void)
 	rwlock_init(&GlobalSMBSeslock);
 	rwlock_init(&cifs_tcp_ses_lock);
 	spin_lock_init(&GlobalMid_Lock);
+	spin_lock_init(&cifs_oplock_lock);
 
 	if (cifs_max_pending < 2) {
 		cifs_max_pending = 2;
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 47f9e06..a2bf6aa 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -654,7 +654,11 @@ GLOBAL_EXTERN rwlock_t		cifs_tcp_ses_lock;
  */
 GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;
 
-GLOBAL_EXTERN struct list_head GlobalOplock_Q;
+/* Global list of oplocks */
+GLOBAL_EXTERN struct list_head cifs_oplock_list;
+
+/* Protects the cifs_oplock_list */
+GLOBAL_EXTERN spinlock_t cifs_oplock_lock;
 
 /* Outstanding dir notify requests */
 GLOBAL_EXTERN struct list_head GlobalDnotifyReqList;
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 551c8f7..9bc5df1 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -135,20 +135,19 @@ AllocOplockQEntry(struct inode *pinode, __u16 fid, struct cifsTconInfo *tcon)
 		temp->pinode = pinode;
 		temp->tcon = tcon;
 		temp->netfid = fid;
-		spin_lock(&GlobalMid_Lock);
-		list_add_tail(&temp->qhead, &GlobalOplock_Q);
-		spin_unlock(&GlobalMid_Lock);
+		spin_lock(&cifs_oplock_lock);
+		list_add_tail(&temp->qhead, &cifs_oplock_list);
+		spin_unlock(&cifs_oplock_lock);
 	}
 	return temp;
-
 }
 
 void DeleteOplockQEntry(struct oplock_q_entry *oplockEntry)
 {
-	spin_lock(&GlobalMid_Lock);
+	spin_lock(&cifs_oplock_lock);
     /* should we check if list empty first? */
 	list_del(&oplockEntry->qhead);
-	spin_unlock(&GlobalMid_Lock);
+	spin_unlock(&cifs_oplock_lock);
 	kmem_cache_free(cifs_oplock_cachep, oplockEntry);
 }
 
@@ -160,14 +159,14 @@ void DeleteTconOplockQEntries(struct cifsTconInfo *tcon)
 	if (tcon == NULL)
 		return;
 
-	spin_lock(&GlobalMid_Lock);
-	list_for_each_entry(temp, &GlobalOplock_Q, qhead) {
+	spin_lock(&cifs_oplock_lock);
+	list_for_each_entry(temp, &cifs_oplock_list, qhead) {
 		if ((temp->tcon) && (temp->tcon == tcon)) {
 			list_del(&temp->qhead);
 			kmem_cache_free(cifs_oplock_cachep, temp);
 		}
 	}
-	spin_unlock(&GlobalMid_Lock);
+	spin_unlock(&cifs_oplock_lock);
 }
 
 static int