[dm-devel] [RFC PATCH v2 2/3] libmultipath: make sysfs_is_multipathed able to return wwid

[Benjamin Marzinski]

sysfs_is_multipathed reads the wwid of the dm device holding a path to
check if its a multipath device.  Add code to optinally set pp->wwid to
that wwid.  This will be used by a future patch.

Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
---
 libmultipath/sysfs.c | 24 +++++++++++++++++++-----
 libmultipath/sysfs.h |  2 +-
 multipath/main.c     |  7 ++++---
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index 62ec2ed7..12a82d95 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -295,7 +295,7 @@ static int select_dm_devs(const struct dirent *di)
 	return fnmatch("dm-*", di->d_name, FNM_FILE_NAME) == 0;
 }
 
-bool sysfs_is_multipathed(const struct path *pp)
+bool sysfs_is_multipathed(struct path *pp, bool set_wwid)
 {
 	char pathbuf[PATH_MAX];
 	struct scandir_result sr;
@@ -325,7 +325,7 @@ bool sysfs_is_multipathed(const struct path *pp)
 	for (i = 0; i < r && !found; i++) {
 		long fd;
 		int nr;
-		char uuid[6];
+		char uuid[WWID_SIZE + UUID_PREFIX_LEN];
 
 		if (safe_snprintf(pathbuf + n, sizeof(pathbuf) - n,
 				  "/%s/dm/uuid", di[i]->d_name))
@@ -339,12 +339,26 @@ bool sysfs_is_multipathed(const struct path *pp)
 
 		pthread_cleanup_push(close_fd, (void *)fd);
 		nr = read(fd, uuid, sizeof(uuid));
-		if (nr == sizeof(uuid) && !memcmp(uuid, "mpath-", sizeof(uuid)))
+		if (nr > (int)UUID_PREFIX_LEN &&
+		    !memcmp(uuid, UUID_PREFIX, UUID_PREFIX_LEN))
 			found = true;
 		else if (nr < 0) {
-			condlog(1, "%s: error reading from %s: %s",
-				__func__, pathbuf, strerror(errno));
+			condlog(1, "%s: error reading from %s: %m",
+				__func__, pathbuf);
 		}
+		if (found && set_wwid) {
+			nr -= UUID_PREFIX_LEN;
+			memcpy(pp->wwid, uuid + UUID_PREFIX_LEN, nr);
+			if (nr == WWID_SIZE) {
+				condlog(4, "%s: overflow while reading from %s",
+					__func__, pathbuf);
+				pp->wwid[0] = '\0';
+			} else {
+				pp->wwid[nr] = '\0';
+				strchop(pp->wwid);
+			}
+                }
+
 		pthread_cleanup_pop(1);
 	}
 	pthread_cleanup_pop(1);
diff --git a/libmultipath/sysfs.h b/libmultipath/sysfs.h
index 9ae30b39..72b39ab2 100644
--- a/libmultipath/sysfs.h
+++ b/libmultipath/sysfs.h
@@ -14,5 +14,5 @@ ssize_t sysfs_bin_attr_get_value(struct udev_device *dev, const char *attr_name,
 				 unsigned char * value, size_t value_len);
 int sysfs_get_size (struct path *pp, unsigned long long * size);
 int sysfs_check_holders(char * check_devt, char * new_devt);
-bool sysfs_is_multipathed(const struct path *pp);
+bool sysfs_is_multipathed(struct path *pp, bool set_wwid);
 #endif
diff --git a/multipath/main.c b/multipath/main.c
index cf9d2a28..545ead87 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -638,7 +638,8 @@ configure (struct config *conf, enum mpath_cmds cmd,
 			 * Shortcut for find_multipaths smart:
 			 * Quick check if path is already multipathed.
 			 */
-			if (sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0))) {
+			if (sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0),
+						 false)) {
 				r = RTVL_YES;
 				goto print_valid;
 			}
@@ -747,8 +748,8 @@ configure (struct config *conf, enum mpath_cmds cmd,
 			/*
 			 * Check if we raced with multipathd
 			 */
-			r = sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0)) ?
-				RTVL_YES : RTVL_NO;
+			r = sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0),
+						 false) ? RTVL_YES : RTVL_NO;
 		}
 		goto print_valid;
 	}
-- 
2.17.2