[Ocfs2-tools-devel] [PATCH 4/6] libo2dlm: Don't drop locks at unlock.

[Joel Becker]

Currently, libo2dlm unlinks files from dlmfs when a lock is unlocked.
This drops the lock in the DLM, losing the contents of the LVB and
removing any lock caching.  While o2dlm holds onto a lock for a few
seconds, no DLM guarantees this will happen.  We don't want that!

Instead, we change o2dlm_unlock() to leave the lock file around in
dlmfs.  This is a truly cached lock.  The calling program can explicitly
drop the lock with o2dlm_drop_lock().  Otherwise, the lock is dropped
when the domain is shut down.

lvb_torture now passes with fsdlm.

Signed-off-by: Joel Becker <joel.becker at oracle.com>
---
 include/o2dlm/o2dlm.h |    4 ++++
 libo2dlm/o2dlm.c      |   44 ++++++++++++++++++++++++++++++++++----------
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/include/o2dlm/o2dlm.h b/include/o2dlm/o2dlm.h
index bb9aca8..2919b23 100644
--- a/include/o2dlm/o2dlm.h
+++ b/include/o2dlm/o2dlm.h
@@ -94,6 +94,10 @@ errcode_t o2dlm_lock_with_bast(struct o2dlm_ctxt *ctxt,
 errcode_t o2dlm_unlock(struct o2dlm_ctxt *ctxt,
 		       const char *lockid);
 
+/* Remove an unlocked lock from the domain */
+errcode_t o2dlm_drop_lock(struct o2dlm_ctxt *ctxt, const char *lockid);
+
+
 /* Read the LVB out of a lock.
  * 'len' is the amount to read into 'lvb'
  *
diff --git a/libo2dlm/o2dlm.c b/libo2dlm/o2dlm.c
index ee7f34c..dbc642b 100644
--- a/libo2dlm/o2dlm.c
+++ b/libo2dlm/o2dlm.c
@@ -509,24 +509,23 @@ static errcode_t o2dlm_lock_classic(struct o2dlm_ctxt *ctxt,
 	return 0;
 }
 
-static errcode_t o2dlm_unlock_lock_res_classic(struct o2dlm_ctxt *ctxt,
-					       struct o2dlm_lock_res *lockres)
+static errcode_t o2dlm_drop_lock_classic(struct o2dlm_ctxt *ctxt,
+					 const char *lockid)
 {
 	int ret, len = PATH_MAX + 1;
 	char *path;
 
-	/* This does the actual unlock. */
-	close(lockres->l_fd);
-
-	/* From here on down, we're trying to unlink the lockres file
-	 * from the dlm file system. Note that EBUSY from unlink is
-	 * not a fatal error here -- it simply means that the lock is
-	 * in use by some other process. */
+	/*
+	 * We're trying to unlink the lockres file from the dlm file
+	 * system. Note that EBUSY from unlink is not a fatal error here
+	 * -- it simply means that the lock is in use by some other
+	 * process.
+	 * */
 	path = malloc(len);
 	if (!path)
 		return O2DLM_ET_NO_MEMORY;
 
-	ret = o2dlm_full_path(path, ctxt, lockres->l_id);
+	ret = o2dlm_full_path(path, ctxt, lockid);
 	if (ret) {
 		free(path);
 		return ret;
@@ -542,6 +541,13 @@ static errcode_t o2dlm_unlock_lock_res_classic(struct o2dlm_ctxt *ctxt,
 	return 0;
 }
 
+static errcode_t o2dlm_unlock_lock_res_classic(struct o2dlm_ctxt *ctxt,
+					       struct o2dlm_lock_res *lockres)
+{
+	close(lockres->l_fd);
+	return 0;
+}
+
 static errcode_t o2dlm_read_lvb_classic(struct o2dlm_ctxt *ctxt,
 					char *lockid,
 					char *lvb,
@@ -1260,6 +1266,24 @@ static errcode_t o2dlm_unlock_lock_res(struct o2dlm_ctxt *ctxt,
 		return o2dlm_unlock_lock_res_fsdlm(ctxt, lockres);
 }
 
+/*
+ * Dropping locks is only available on dlmfs.  No one should be using
+ * libdlm if they can help it.
+ */
+errcode_t o2dlm_drop_lock(struct o2dlm_ctxt *ctxt, const char *lockid)
+{
+	if (!ctxt || !lockid)
+		return O2DLM_ET_INVALID_ARGS;
+
+	if (o2dlm_find_lock_res(ctxt, lockid))
+		return O2DLM_ET_BUSY_LOCK;
+
+	if (ctxt->ct_classic)
+		return o2dlm_drop_lock_classic(ctxt, lockid);
+	else
+		return O2DLM_ET_SERVICE_UNAVAILABLE;
+}
+
 errcode_t o2dlm_unlock(struct o2dlm_ctxt *ctxt,
 		       const char *lockid)
 {
-- 
1.6.6.1