[dm-devel] [PATCH v2 09/21] multipath-tools: don't call dm_lib_release() any more

[mwilck at suse.com]

From: Martin Wilck <mwilck at suse.com>

The purpose of dm_lib_release() is to release stacked device node
operations in libdevmapper. This is functionality we don't need and
use any more, as we rely on udev to set up device nodes and symlinks.

We always set DM_UDEV_DISABLE_LIBRARY_FALLBACK when we run dm tasks.
In the standard CREATE and REMOVE cases, libdevmapper doesn't
stack any operations if this flag is set. The only exceptions are

 a) RESUME operations with DM_ADD_NODE_ON_RESUME set. This happens
implicity when we create new maps
 b) RENAME operations

In both cases, we call dm_udev_wait() after the libdm operation, which
calls update_devs() and thus has the same effect as dm_lib_release(),
cleaning out stacked operations.

OTOH, dm_lib_releases() accesses static variables in libdevmapper, so
calling it might be racy.

Drop the calls to dm_lib_release().

Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>
Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 kpartx/kpartx.c                 |  1 -
 libmpathpersist/mpath_persist.c |  1 -
 multipath/main.c                |  1 -
 multipathd/cli_handlers.c       |  2 --
 multipathd/main.c               | 15 ++-------------
 5 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/kpartx/kpartx.c b/kpartx/kpartx.c
index 4a0aae9..6a7933f 100644
--- a/kpartx/kpartx.c
+++ b/kpartx/kpartx.c
@@ -681,7 +681,6 @@ main(int argc, char **argv){
 	}
 
 end:
-	dm_lib_release();
 	dm_lib_exit();
 
 	return r;
diff --git a/libmpathpersist/mpath_persist.c b/libmpathpersist/mpath_persist.c
index 1f9817e..39055ed 100644
--- a/libmpathpersist/mpath_persist.c
+++ b/libmpathpersist/mpath_persist.c
@@ -56,7 +56,6 @@ mpath_lib_init (void)
 int
 mpath_lib_exit (struct config *conf)
 {
-	dm_lib_release();
 	dm_lib_exit();
 	cleanup_prio();
 	cleanup_checkers();
diff --git a/multipath/main.c b/multipath/main.c
index 9e920d8..dc4974b 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -1063,7 +1063,6 @@ main (int argc, char *argv[])
 		condlog(3, "restart multipath configuration process");
 
 out:
-	dm_lib_release();
 	dm_lib_exit();
 
 	cleanup_foreign();
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index 235e2a2..5463573 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -860,7 +860,6 @@ cli_add_map (void * v, char ** reply, int * len, void * data)
 				    != CP_OK)
 					condlog(2, "%s: coalesce_paths failed",
 									param);
-				dm_lib_release();
 				FREE(refwwid);
 			}
 		} /*we attempt to create device only once*/
@@ -1032,7 +1031,6 @@ cli_resize(void *v, char **reply, int *len, void *data)
 	if (resize_map(mpp, size, vecs) != 0)
 		return 1;
 
-	dm_lib_release();
 	if (setup_multipath(vecs, mpp) != 0)
 		return 1;
 	sync_map_state(mpp);
diff --git a/multipathd/main.c b/multipathd/main.c
index d1f8cc1..5cc3435 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -510,7 +510,6 @@ retry:
 		sleep(1);
 		goto retry;
 	}
-	dm_lib_release();
 
 fail:
 	if (new_map && (retries < 0 || wait_for_events(mpp, vecs))) {
@@ -611,10 +610,8 @@ coalesce_maps(struct vectors *vecs, vector nmpv)
 				vector_del_slot(ompv, i);
 				i--;
 			}
-			else {
-				dm_lib_release();
+			else
 				condlog(2, "%s devmap removed", ompp->alias);
-			}
 		} else if (reassign_maps) {
 			condlog(3, "%s: Reassign existing device-mapper"
 				" devices", ompp->alias);
@@ -660,10 +657,8 @@ flush_map(struct multipath * mpp, struct vectors * vecs, int nopaths)
 		}
 		return r;
 	}
-	else {
-		dm_lib_release();
+	else
 		condlog(2, "%s: map flushed", mpp->alias);
-	}
 
 	orphan_paths(vecs->pathvec, mpp, "map flushed");
 	remove_map_and_stop_waiter(mpp, vecs);
@@ -1080,7 +1075,6 @@ rescan:
 		else
 			goto fail_map;
 	}
-	dm_lib_release();
 
 	if ((mpp->action == ACT_CREATE ||
 	     (mpp->action == ACT_NOTHING && start_waiter && !mpp->waiter)) &&
@@ -1947,8 +1941,6 @@ int reload_and_sync_map(struct multipath *mpp,
 {
 	if (reload_map(vecs, mpp, refresh, 1))
 		return 1;
-
-	dm_lib_release();
 	if (setup_multipath(vecs, mpp) != 0)
 		return 2;
 	sync_map_state(mpp);
@@ -2631,8 +2623,6 @@ configure (struct vectors * vecs)
 		goto fail;
 	}
 
-	dm_lib_release();
-
 	if (should_exit())
 		goto fail;
 
@@ -3115,7 +3105,6 @@ child (__attribute__((unused)) void *param)
 	if (poll_dmevents)
 		cleanup_dmevent_waiter();
 
-	dm_lib_release();
 	dm_lib_exit();
 
 	/* We're done here */
-- 
2.28.0