[Ocfs2-devel] [PATCH] ocfs2: unlock open_lock immediately

[Wengang Wang]

There is a race between 2(+) nodes that calls iput_final() on same inode.
time sequence is like the following. The result is neither of the 2(+) node
does real inode deletion work and the unlinked inode is left in orphandir. 

--------------------------------------

node A                                  node B

open_lock PR

                                        open_LOCK PR

.......

                                         .......

#in ocfs2_delete_inode()
inode_lock EX
#in ocfs2_query_inode_wipe
try open_lock EX -->cant grant(B has PR)
ignore the deletion
inode_unlock EX

                                        #in ocfs2_delete_inode() 
                                        inode_lock EX
                                        #in ocfs2_query_inode_wipe
                                        try open_lock EX -->can't grant(A has PR)
                                        ignore the deletion
                                        inode_unlock EX

#in ocfs2_clear_inode()
open_unlock EX
drop open_lock

                                         #in ocfs2_clear_inode()
                                         open_unlock EX

--------------------------------------

The fix is to force dlm_unlock on open_lock within inode_lock. see
comment embedded in patch.

Signed-off-by: Wengang Wang <wen.gang.wang at oracle.com>
---
 fs/ocfs2/dlmglue.c |    8 ++++++--
 fs/ocfs2/inode.c   |   11 +++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 7642d7c..f331310 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -1752,12 +1752,16 @@ void ocfs2_open_unlock(struct inode *inode)
 	if (ocfs2_mount_local(osb))
 		goto out;
 
-	if(lockres->l_ro_holders)
+	if (lockres->l_ro_holders) {
 		ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres,
 				     DLM_LOCK_PR);
-	if(lockres->l_ex_holders)
+		lockres->l_ro_holders = 0;
+	}
+	if (lockres->l_ex_holders) {
 		ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres,
 				     DLM_LOCK_EX);
+		lockres->l_ex_holders = 0;
+	}
 
 out:
 	return;
diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index b4c8bb6..390a6fc 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1052,6 +1052,17 @@ static void ocfs2_delete_inode(struct inode *inode)
 	OCFS2_I(inode)->ip_flags |= OCFS2_INODE_DELETED;
 
 bail_unlock_inode:
+	/*
+	 * since we don't take care of deleting the on disk inode any longer
+	 * from now on, we must release the open_lock(dlm unlock) immediately
+	 * within inode_lock. Otherwise, trying open_lock for EX from other node
+	 * can fail if it comes before we release PR on open_lock later, so that
+	 * both/all nodes think other node(s) is/are opening the inode thus
+	 * neither/none of them do real inode deletion.
+	 */
+	ocfs2_open_unlock(inode);
+	ocfs2_simple_drop_lockres(OCFS2_SB(inode->i_sb),
+				  &OCFS2_I(inode)->ip_open_lockres);
 	ocfs2_inode_unlock(inode, 1);
 	brelse(di_bh);
 
-- 
1.7.5.2