diff options
| -rw-r--r-- | fs/ocfs2/dlmglue.c | 119 | ||||
| -rw-r--r-- | fs/ocfs2/dlmglue.h | 1 |
2 files changed, 90 insertions, 30 deletions
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 @@ -788,35 +788,34 @@ static inline void ocfs2_add_holder(struct ocfs2_lock_res *lockres, spin_unlock(&lockres->l_lock); } -static inline void ocfs2_remove_holder(struct ocfs2_lock_res *lockres, - struct ocfs2_lock_holder *oh) -{ - spin_lock(&lockres->l_lock); - list_del(&oh->oh_list); - spin_unlock(&lockres->l_lock); - - put_pid(oh->oh_owner_pid); -} - -static inline int ocfs2_is_locked_by_me(struct ocfs2_lock_res *lockres) +static struct ocfs2_lock_holder * +ocfs2_pid_holder(struct ocfs2_lock_res *lockres, + struct pid *pid) { 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; + return oh; } } spin_unlock(&lockres->l_lock); + return NULL; +} - return 0; +static inline void ocfs2_remove_holder(struct ocfs2_lock_res *lockres, + struct ocfs2_lock_holder *oh) +{ + spin_lock(&lockres->l_lock); + list_del(&oh->oh_list); + spin_unlock(&lockres->l_lock); + + put_pid(oh->oh_owner_pid); } + 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; } - } - if (!has_locked) + + oh->oh_ex = ex; ocfs2_add_holder(lockres, oh); + return 0; + } - return has_locked; + 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; + } + } + 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 */ |