diff mbox series

[2/2] libmultipath: fix false removes in dmevents polling code

Message ID 1543385604-25453-2-git-send-email-bmarzins@redhat.com (mailing list archive)
State Not Applicable, archived
Delegated to: christophe varoqui
Headers show
Series [1/2] libmultipath: cleanup pthread_cleanup_pop call | expand

Commit Message

Benjamin Marzinski Nov. 28, 2018, 6:13 a.m. UTC 
dm_is_mpath() would return 0 if either a device was not a multipath
device or if the libdevmapper command failed. Because dm_is_mpath()
didn't distinguish between these situations, dm_get_events() could
assume that a device was not really a multipath device, when in fact it
was, and the libdevmapper command simply failed. This would cause the
dmevents polling waiter to stop monitoring the device.

In reality, the call to dm_is_mpath() isn't necessary, because
dm_get_events() will already verify that the device name is on the list
of devices to wait for. However, if there are a large number of
non-multipath devices on the system, ignoring them can be useful.  Thus,
if dm_is_mpath() successfully runs the libdevmapper command and verifies
that the device is not a multipath device, dm_get_events() should skip
it. But if the libdevmapper command fails, dm_get_events() should still
check the device list, to see if the device should be monitored.

This commit makes dm_is_mpath() return -1 for situations where
the libdevmapper command failed, and makes dm_get_events() only ignore
the device on a return of 0.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
 libmpathpersist/mpath_persist.c |  4 ++--
 libmultipath/devmapper.c        | 26 ++++++++++++++++++++------
 multipath/main.c                |  2 +-
 multipathd/dmevents.c           |  4 +++-
 multipathd/main.c               |  2 +-
 5 files changed, 27 insertions(+), 11 deletions(-)

Comments

Martin Wilck Nov. 28, 2018, 9:08 a.m. UTC | #1 
On Wed, 2018-11-28 at 00:13 -0600,  Benjamin Marzinski  wrote:
> dm_is_mpath() would return 0 if either a device was not a multipath
> device or if the libdevmapper command failed. Because dm_is_mpath()
> didn't distinguish between these situations, dm_get_events() could
> assume that a device was not really a multipath device, when in fact
> it
> was, and the libdevmapper command simply failed. This would cause the
> dmevents polling waiter to stop monitoring the device.
> 
> In reality, the call to dm_is_mpath() isn't necessary, because
> dm_get_events() will already verify that the device name is on the
> list
> of devices to wait for. However, if there are a large number of
> non-multipath devices on the system, ignoring them can be
> useful.  Thus,
> if dm_is_mpath() successfully runs the libdevmapper command and
> verifies
> that the device is not a multipath device, dm_get_events() should
> skip
> it. But if the libdevmapper command fails, dm_get_events() should
> still
> check the device list, to see if the device should be monitored.
> 
> This commit makes dm_is_mpath() return -1 for situations where
> the libdevmapper command failed, and makes dm_get_events() only
> ignore
> the device on a return of 0.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> ---

Two minor remarks:

1. You've changed dm_is_mpath() calls from "if (!result)" to 
"if (result == 0)" or "if (result != 1)" syntax, but you missed the
call in watch_dmevents(). I suggest that, for clarity, you change that
one as well.

2. We should add a condlog(2,...) to dm_is_mpath() if it returns -1.

Otherwise, ACK.

Martin


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diff mbox series

Patch

diff --git a/libmpathpersist/mpath_persist.c b/libmpathpersist/mpath_persist.c
index 2ffe56e..7e8a676 100644
--- a/libmpathpersist/mpath_persist.c
+++ b/libmpathpersist/mpath_persist.c
@@ -188,7 +188,7 @@  int mpath_persistent_reserve_in (int fd, int rq_servact,
 
 	condlog(3, "alias = %s", alias);
 	map_present = dm_map_present(alias);
-	if (map_present && !dm_is_mpath(alias)){
+	if (map_present && dm_is_mpath(alias) != 1){
 		condlog( 0, "%s: not a multipath device.", alias);
 		ret = MPATH_PR_DMMP_ERROR;
 		goto out;
@@ -283,7 +283,7 @@  int mpath_persistent_reserve_out ( int fd, int rq_servact, int rq_scope,
 	condlog(3, "alias = %s", alias);
 	map_present = dm_map_present(alias);
 
-	if (map_present && !dm_is_mpath(alias)){
+	if (map_present && dm_is_mpath(alias) != 1){
 		condlog(3, "%s: not a multipath device.", alias);
 		ret = MPATH_PR_DMMP_ERROR;
 		goto out;
diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index 0433b49..0e98923 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -692,9 +692,15 @@  out:
 	return r;
 }
 
+/*
+ * returns:
+ * 1  : is multipath device
+ * 0  : is not multipath device
+ * -1 : error
+ */
 int dm_is_mpath(const char *name)
 {
-	int r = 0;
+	int r = -1;
 	struct dm_task *dmt;
 	struct dm_info info;
 	uint64_t start, length;
@@ -703,7 +709,7 @@  int dm_is_mpath(const char *name)
 	const char *uuid;
 
 	if (!(dmt = libmp_dm_task_create(DM_DEVICE_TABLE)))
-		return 0;
+		return -1;
 
 	if (!dm_task_set_name(dmt, name))
 		goto out;
@@ -713,7 +719,12 @@  int dm_is_mpath(const char *name)
 	if (!dm_task_run(dmt))
 		goto out;
 
-	if (!dm_task_get_info(dmt, &info) || !info.exists)
+	if (!dm_task_get_info(dmt, &info))
+		goto out;
+
+	r = 0;
+
+	if (!info.exists)
 		goto out;
 
 	uuid = dm_task_get_uuid(dmt);
@@ -722,7 +733,10 @@  int dm_is_mpath(const char *name)
 		goto out;
 
 	/* Fetch 1st target */
-	dm_get_next_target(dmt, NULL, &start, &length, &target_type, &params);
+	if (dm_get_next_target(dmt, NULL, &start, &length, &target_type,
+			       &params) != NULL)
+		/* multiple targets */
+		goto out;
 
 	if (!target_type || strcmp(target_type, TGT_MPATH) != 0)
 		goto out;
@@ -823,7 +837,7 @@  int _dm_flush_map (const char * mapname, int need_sync, int deferred_remove,
 	unsigned long long mapsize;
 	char params[PARAMS_SIZE] = {0};
 
-	if (!dm_is_mpath(mapname))
+	if (dm_is_mpath(mapname) != 1)
 		return 0; /* nothing to do */
 
 	/* if the device currently has no partitions, do not
@@ -1087,7 +1101,7 @@  dm_get_maps (vector mp)
 	}
 
 	do {
-		if (!dm_is_mpath(names->name))
+		if (dm_is_mpath(names->name) != 1)
 			goto next;
 
 		mpp = dm_get_multipath(names->name);
diff --git a/multipath/main.c b/multipath/main.c
index 05b7bf0..98fee1c 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -319,7 +319,7 @@  static int check_usable_paths(struct config *conf,
 		goto out;
 	}
 
-	if (!dm_is_mpath(mapname)) {
+	if (dm_is_mpath(mapname) != 1) {
 		condlog(1, "%s is not a multipath map", devpath);
 		goto free;
 	}
diff --git a/multipathd/dmevents.c b/multipathd/dmevents.c
index 31e64a7..aae7a09 100644
--- a/multipathd/dmevents.c
+++ b/multipathd/dmevents.c
@@ -168,7 +168,9 @@  static int dm_get_events(void)
 	while (names->dev) {
 		uint32_t event_nr;
 
-		if (!dm_is_mpath(names->name))
+		/* Don't delete device if dm_is_mpath() fails without
+		 * checking the device type */
+		if (dm_is_mpath(names->name) == 0)
 			goto next;
 
 		event_nr = dm_event_nr(names);
diff --git a/multipathd/main.c b/multipathd/main.c
index 2e5f9ed..c781115 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -699,7 +699,7 @@  ev_add_map (char * dev, const char * alias, struct vectors * vecs)
 	int delayed_reconfig, reassign_maps;
 	struct config *conf;
 
-	if (!dm_is_mpath(alias)) {
+	if (dm_is_mpath(alias) != 1) {
 		condlog(4, "%s: not a multipath map", alias);
 		return 0;
 	}