diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 97a972efab83..68728de12864 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -788,6 +788,23 @@ static inline void ocfs2_add_holder(struct ocfs2_lock_res *lockres,
spin_unlock(&lockres->l_lock);
}
+static struct ocfs2_lock_holder *
+ocfs2_pid_holder(struct ocfs2_lock_res *lockres,
+ struct pid *pid)
+{
+ struct ocfs2_lock_holder *oh;
+
+ spin_lock(&lockres->l_lock);
+ list_for_each_entry(oh, &lockres->l_holders, oh_list) {
+ if (oh->oh_owner_pid == pid) {
+ spin_unlock(&lockres->l_lock);
+ return oh;
+ }
+ }
+ spin_unlock(&lockres->l_lock);
+ return NULL;
+}
+
static inline void ocfs2_remove_holder(struct ocfs2_lock_res *lockres,
struct ocfs2_lock_holder *oh)
{
@@ -798,24 +815,6 @@ static inline void ocfs2_remove_holder(struct ocfs2_lock_res *lockres,
put_pid(oh->oh_owner_pid);
}
-static inline int ocfs2_is_locked_by_me(struct ocfs2_lock_res *lockres)
-{
- struct ocfs2_lock_holder *oh;
- struct pid *pid;
-
- /* look in the list of holders for one with the current task as owner */
- spin_lock(&lockres->l_lock);
- pid = task_pid(current);
- list_for_each_entry(oh, &lockres->l_holders, oh_list) {
- if (oh->oh_owner_pid == pid) {
- spin_unlock(&lockres->l_lock);
- return 1;
- }
- }
- spin_unlock(&lockres->l_lock);
-
- return 0;
-}
static inline void ocfs2_inc_holders(struct ocfs2_lock_res *lockres,
int level)
@@ -2610,34 +2609,93 @@ void ocfs2_inode_unlock(struct inode *inode,
*
* return < 0 on error, return == 0 if there's no lock holder on the stack
* before this call, return == 1 if this call would be a recursive locking.
+ * return == -1 if this lock attempt will cause an upgrade which is forbidden.
+ *
+ * When taking lock levels into account,we face some different situations.
+ *
+ * 1. no lock is held
+ * In this case, just lock the inode as requested and return 0
+ *
+ * 2. We are holding a lock
+ * For this situation, things diverges into several cases
+ *
+ * wanted holding what to do
+ * ex ex see 2.1 below
+ * ex pr see 2.2 below
+ * pr ex see 2.1 below
+ * pr pr see 2.1 below
+ *
+ * 2.1 lock level that is been held is compatible
+ * with the wanted level, so no lock action will be tacken.
+ *
+ * 2.2 Otherwise, an upgrade is needed, but it is forbidden.
+ *
+ * Reason why upgrade within a process is forbidden is that
+ * lock upgrade may cause dead lock. The following illustrates
+ * how it happens.
+ *
+ * thread on node1 thread on node2
+ * ocfs2_inode_lock_tracker(ex=0)
+ *
+ * <====== ocfs2_inode_lock_tracker(ex=1)
+ *
+ * ocfs2_inode_lock_tracker(ex=1)
*/
int ocfs2_inode_lock_tracker(struct inode *inode,
struct buffer_head **ret_bh,
int ex,
struct ocfs2_lock_holder *oh)
{
- int status;
- int arg_flags = 0, has_locked;
+ int status = 0;
struct ocfs2_lock_res *lockres;
+ struct ocfs2_lock_holder *tmp_oh;
+ struct pid *pid = task_pid(current);
+
lockres = &OCFS2_I(inode)->ip_inode_lockres;
- has_locked = ocfs2_is_locked_by_me(lockres);
- /* Just get buffer head if the cluster lock has been taken */
- if (has_locked)
- arg_flags = OCFS2_META_LOCK_GETBH;
+ tmp_oh = ocfs2_pid_holder(lockres, pid);
- if (likely(!has_locked || ret_bh)) {
- status = ocfs2_inode_lock_full(inode, ret_bh, ex, arg_flags);
+ if (!tmp_oh) {
+ /*
+ * This corresponds to the case 1.
+ * We haven't got any lock before.
+ */
+ status = ocfs2_inode_lock_full(inode, ret_bh, ex, 0);
+ if (status < 0) {
+ if (status != -ENOENT)
+ mlog_errno(status);
+ return status;
+ }
+
+ oh->oh_ex = ex;
+ ocfs2_add_holder(lockres, oh);
+ return 0;
+ }
+
+ if (unlikely(ex && !tmp_oh->oh_ex)) {
+ /*
+ * case 2.2 upgrade may cause dead lock, forbid it.
+ */
+ mlog(ML_ERROR, "Recursive locking is not permitted to "
+ "upgrade to EX level from PR level.\n");
+ dump_stack();
+ return -EINVAL;
+ }
+
+ /*
+ * case 2.1 OCFS2_META_LOCK_GETBH flag make ocfs2_inode_lock_full.
+ * ignore the lock level and just update it.
+ */
+ if (ret_bh) {
+ status = ocfs2_inode_lock_full(inode, ret_bh, ex,
+ OCFS2_META_LOCK_GETBH);
if (status < 0) {
if (status != -ENOENT)
mlog_errno(status);
return status;
}
}
- if (!has_locked)
- ocfs2_add_holder(lockres, oh);
-
- return has_locked;
+ return tmp_oh ? 1 : 0;
}
void ocfs2_inode_unlock_tracker(struct inode *inode,
@@ -2649,12 +2707,13 @@ void ocfs2_inode_unlock_tracker(struct inode *inode,
lockres = &OCFS2_I(inode)->ip_inode_lockres;
/* had_lock means that the currect process already takes the cluster
- * lock previously. If had_lock is 1, we have nothing to do here, and
- * it will get unlocked where we got the lock.
+ * lock previously.
+ * If had_lock is 1, we have nothing to do here.
+ * If had_lock is 0, we will release the lock.
*/
if (!had_lock) {
+ ocfs2_inode_unlock(inode, oh->oh_ex);
ocfs2_remove_holder(lockres, oh);
- ocfs2_inode_unlock(inode, ex);
}
}
diff --git a/fs/ocfs2/dlmglue.h b/fs/ocfs2/dlmglue.h
index 256e0a9067b8..4ec1c828f6e0 100644
--- a/fs/ocfs2/dlmglue.h
+++ b/fs/ocfs2/dlmglue.h
@@ -96,6 +96,7 @@ struct ocfs2_trim_fs_info {
struct ocfs2_lock_holder {
struct list_head oh_list;
struct pid *oh_owner_pid;
+ int oh_ex;
};
/* ocfs2_inode_lock_full() 'arg_flags' flags */