With "find_multipaths smart", we accept paths as valid if they are
already part of a multipath map. This patch avoids doing a full path
and device-mapper map scan for this case, speeding up "multipath -u"
considerably.

Signed-off-by: Martin Wilck <mwi...@suse.com>
Reviewed-by: Benjamin Marzinski <bmarz...@redhat.com>
---
 libmultipath/sysfs.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 libmultipath/sysfs.h |  2 ++
 multipath/main.c     |  9 +++++++
 3 files changed, 77 insertions(+)

diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index 97e09977..ee72e6a3 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -27,6 +27,7 @@
 #include <string.h>
 #include <dirent.h>
 #include <libudev.h>
+#include <fnmatch.h>
 
 #include "checkers.h"
 #include "vector.h"
@@ -287,3 +288,68 @@ int sysfs_check_holders(char * check_devt, char * new_devt)
 
        return 0;
 }
+
+static int select_dm_devs(const struct dirent *di)
+{
+       return fnmatch("dm-*", di->d_name, FNM_FILE_NAME) == 0;
+}
+
+static void close_fd(void *arg)
+{
+       close((long)arg);
+}
+
+bool sysfs_is_multipathed(const struct path *pp)
+{
+       char pathbuf[PATH_MAX];
+       struct dirent **di;
+       int n, r, i;
+       bool found = false;
+
+       n = snprintf(pathbuf, sizeof(pathbuf), "/sys/block/%s/holders",
+                    pp->dev);
+
+       if (n >= sizeof(pathbuf)) {
+               condlog(1, "%s: pathname overflow", __func__);
+               return false;
+       }
+
+       r = scandir(pathbuf, &di, select_dm_devs, alphasort);
+       if (r == 0)
+               return false;
+       else if (r < 0) {
+               condlog(1, "%s: error scanning %s", __func__, pathbuf);
+               return false;
+       }
+
+       pthread_cleanup_push(free, di);
+       for (i = 0; i < r && !found; i++) {
+               long fd;
+               int nr;
+               char uuid[6];
+
+               if (snprintf(pathbuf + n, sizeof(pathbuf) - n,
+                            "/%s/dm/uuid", di[i]->d_name)
+                   >= sizeof(pathbuf) - n)
+                       continue;
+
+               fd = open(pathbuf, O_RDONLY);
+               if (fd == -1) {
+                       condlog(1, "%s: error opening %s", __func__, pathbuf);
+                       continue;
+               }
+
+               pthread_cleanup_push(close_fd, (void *)fd);
+               nr = read(fd, uuid, sizeof(uuid));
+               if (nr == sizeof(uuid) && !memcmp(uuid, "mpath-", sizeof(uuid)))
+                       found = true;
+               else if (nr < 0) {
+                       condlog(1, "%s: error reading from %s: %s",
+                               __func__, pathbuf, strerror(errno));
+               }
+               pthread_cleanup_pop(1);
+       }
+       pthread_cleanup_pop(1);
+
+       return found;
+}
diff --git a/libmultipath/sysfs.h b/libmultipath/sysfs.h
index 75c0f9c1..9ae30b39 100644
--- a/libmultipath/sysfs.h
+++ b/libmultipath/sysfs.h
@@ -4,6 +4,7 @@
 
 #ifndef _LIBMULTIPATH_SYSFS_H
 #define _LIBMULTIPATH_SYSFS_H
+#include <stdbool.h>
 
 ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
                             const char * value, size_t value_len);
@@ -13,4 +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);
 #endif
diff --git a/multipath/main.c b/multipath/main.c
index 61ba90a6..96e37a7a 100644
--- a/multipath/main.c
+++ b/multipath/main.c
@@ -593,6 +593,15 @@ configure (struct config *conf, enum mpath_cmds cmd,
                        if (!ignore_wwids_on(conf))
                                goto print_valid;
                        /* At this point, either r==0 or find_multipaths_on. */
+
+                       /*
+                        * Shortcut for find_multipaths smart:
+                        * Quick check if path is already multipathed.
+                        */
+                       if (sysfs_is_multipathed(VECTOR_SLOT(pathvec, 0))) {
+                               r = 0;
+                               goto print_valid;
+                       }
                        if (r == 0)
                                goto print_valid;
                        /* find_multipaths_on: Fall through to path detection */
-- 
2.16.1

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