Add -c to zpool iostat & status to run command

This patch adds a command (-c) option to zpool status and zpool iostat.  The
-c option allows you to run an arbitrary command on each vdev and display
the first line of output in zpool status/iostat.  The environment vars
VDEV_PATH and VDEV_UPATH are set to the vdev's path and "underlying path"
before running the command.  For device mapper, multipath, or partitioned
vdevs, VDEV_UPATH is the actual underlying /dev/sd* disk.  This can be useful
if the command you're running requires a /dev/sd* device.

The patch also uses /sys/block/<dev>/slaves/ to lookup the underlying device
instead of using libdevmapper.  This not only removes the libdevmapper
requirement at build time, but also allows you to resolve device mapper
devices without being root.  This means that UDEV_UPATH get set correctly
when running zpool status/iostat as an unprivileged user.

Example:

$ zpool status -c 'echo I am $VDEV_PATH, $VDEV_UPATH'

NAME        STATE     READ WRITE CKSUM
mypool      ONLINE       0     0     0
  mirror-0  ONLINE       0     0     0
    mpatha  ONLINE       0     0     0  I am /dev/mapper/mpatha, /dev/sdc
    sdb     ONLINE       0     0     0  I am /dev/sdb1, /dev/sdb

Reviewed-by: Giuseppe Di Natale <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tony Hutter <[email protected]>
Closes #5368 

2 files changed, 88 insertions, 97 deletions

diff --git a/lib/libzfs/Makefile.am b/lib/libzfs/Makefile.am
index 8e596b001..f1260ea71 100644
--- a/lib/libzfs/Makefile.am
+++ b/lib/libzfs/Makefile.am
@@ -35,7 +35,7 @@ libzfs_la_LIBADD = \
 	$(top_builddir)/lib/libnvpair/libnvpair.la \
 	$(top_builddir)/lib/libzpool/libzpool.la
 
-libzfs_la_LIBADD += -lm $(LIBBLKID) $(LIBUDEV) $(LIBDEVMAPPER)
+libzfs_la_LIBADD += -lm $(LIBBLKID) $(LIBUDEV)
 libzfs_la_LDFLAGS = -version-info 2:0:0
 
 EXTRA_DIST = $(libzfs_pc_DATA) $(USER_C)
diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index 6727a77e7..9d0702b56 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -41,9 +41,6 @@
 #include <sys/vtoc.h>
 #include <sys/zfs_ioctl.h>
 #include <dlfcn.h>
-#if HAVE_LIBDEVMAPPER
-#include <libdevmapper.h>
-#endif
 
 #include "zfs_namecheck.h"
 #include "zfs_prop.h"
@@ -3432,6 +3429,43 @@ zfs_strip_partition(char *path)
 	return (tmp);
 }
 
+/*
+ * Same as zfs_strip_partition, but allows "/dev/" to be in the pathname
+ *
+ * path:	/dev/sda1
+ * returns:	/dev/sda
+ *
+ * Returned string must be freed.
+ */
+char *
+zfs_strip_partition_path(char *path)
+{
+	char *newpath = strdup(path);
+	char *sd_offset;
+	char *new_sd;
+
+	if (!newpath)
+		return (NULL);
+
+	/* Point to "sda1" part of "/dev/sda1" */
+	sd_offset = strrchr(newpath, '/') + 1;
+
+	/* Get our new name "sda" */
+	new_sd = zfs_strip_partition(sd_offset);
+	if (!new_sd) {
+		free(newpath);
+		return (NULL);
+	}
+
+	/* Paste the "sda" where "sda1" was */
+	strlcpy(sd_offset, new_sd, strlen(sd_offset) + 1);
+
+	/* Free temporary "sda" */
+	free(new_sd);
+
+	return (newpath);
+}
+
 #define	PATH_BUF_LEN	64
 
 /*
@@ -4318,112 +4352,69 @@ zpool_label_disk(libzfs_handle_t *hdl, zpool_handle_t *zhp, char *name)
 	return (0);
 }
 
-#if HAVE_LIBDEVMAPPER
-static void libdevmapper_dummy_log(int level, const char *file, int line,
-    int dm_errno_or_class, const char *f, ...) {}
-
-/* Disable libdevmapper error logging */
-static void disable_libdevmapper_errors(void) {
-	dm_log_with_errno_init(libdevmapper_dummy_log);
-}
-/* Enable libdevmapper error logging */
-static void enable_libdevmapper_errors(void) {
-	dm_log_with_errno_init(NULL);
-}
-#endif
-
 /*
  * Allocate and return the underlying device name for a device mapper device.
  * If a device mapper device maps to multiple devices, return the first device.
  *
- * For example, dm_name = "/dev/dm-0" could return "/dev/sda"
- *
- * dm_name should include the "/dev[/mapper]" prefix.
+ * For example, dm_name = "/dev/dm-0" could return "/dev/sda". Symlinks to a
+ * DM device (like /dev/disk/by-vdev/A0) are also allowed.
  *
  * Returns device name, or NULL on error or no match.  If dm_name is not a DM
  * device then return NULL.
  *
  * NOTE: The returned name string must be *freed*.
  */
-static char * dm_get_underlying_path(char *dm_name)
+char *
+dm_get_underlying_path(char *dm_name)
 {
-	char *name = NULL;
-#if HAVE_LIBDEVMAPPER
-	char *tmp;
-	struct dm_task *dmt = NULL;
-	struct dm_tree *dt = NULL;
-	struct dm_tree_node *root, *child;
-	void *handle = NULL;
-	struct dm_info info;
-	const struct dm_info *child_info;
+	DIR *dp = NULL;
+	struct dirent *ep;
+	char *realp;
+	char *tmp = NULL;
+	char *path = NULL;
+	char *dev_str;
+	int size;
 
-	/*
-	 * Disable libdevmapper errors.  It's entirely possible user is not
-	 * running devmapper, or that dm_name is not a devmapper device.
-	 * That's totally ok, we will just harmlessly and silently return NULL.
-	 */
-	disable_libdevmapper_errors();
+	if (dm_name == NULL)
+		return (NULL);
+
+	/* dm name may be a symlink (like /dev/disk/by-vdev/A0) */
+	realp = realpath(dm_name, NULL);
+	if (realp == NULL)
+		return (NULL);
 
 	/*
-	 * libdevmapper tutorial
-	 *
-	 * libdevmapper is basically a fancy wrapper for its ioctls.  You
-	 * create a "task", fill in the needed info to the task (fill in the
-	 * ioctl fields), then run the task (call the ioctl).
-	 *
-	 * First we need the major/minor number for our DM device.
+	 * If they preface 'dev' with a path (like "/dev") then strip it off.
+	 * We just want the 'dm-N' part.
 	 */
-	if (!(dmt = dm_task_create(DM_DEVICE_INFO)))
-		goto end;
-
-	/* Lookup the name in libdevmapper */
-	if (!dm_task_set_name(dmt, dm_name)) {
-		enable_libdevmapper_errors();
-		goto end;
-	}
-
-	if (!dm_task_run(dmt))
-		goto end;
-
-	/* Get DM device's major/minor */
-	if (!dm_task_get_info(dmt, &info))
-		goto end;
-
-	/* We have major/minor number.  Lookup the dm device's children */
-	if (!(dt = dm_tree_create()))
-		goto end;
-
-	/* We add the device into the tree and its children get populated */
-	if (!dm_tree_add_dev(dt, info.major, info.minor))
-		goto end;
-
-	if (!(root = dm_tree_find_node(dt, 0, 0)))
-		goto end;
-
-	if (!(child = dm_tree_next_child(&handle, root, 1)))
-		goto end;
+	tmp = strrchr(realp, '/');
+	if (tmp != NULL)
+		dev_str = tmp + 1;    /* +1 since we want the chr after '/' */
+	else
+		dev_str = tmp;
 
-	/* Get child's major/minor numbers */
-	if (!(child_info = dm_tree_node_get_info(child)))
+	size = asprintf(&tmp, "/sys/block/%s/slaves/", dev_str);
+	if (size == -1 || !tmp)
 		goto end;
 
-	if ((asprintf(&tmp, "/dev/block/%d:%d", child_info->major,
-	    child_info->minor) == -1) || tmp == NULL)
+	dp = opendir(tmp);
+	if (dp == NULL)
 		goto end;
 
-	/* Further translate /dev/block/ name into the normal name */
-	name = realpath(tmp, NULL);
-	free(tmp);
+	/* Return first sd* entry in /sys/block/dm-N/slaves/ */
+	while ((ep = readdir(dp))) {
+		if (ep->d_type != DT_DIR) {	/* skip "." and ".." dirs */
+			size = asprintf(&path, "/dev/%s", ep->d_name);
+			break;
+		}
+	}
 
 end:
-	if (dmt)
-		dm_task_destroy(dmt);
-	if (dt)
-		dm_tree_free(dt);
-	enable_libdevmapper_errors();
-#endif /* HAVE_LIBDEVMAPPER */
-
-	return (name);
+	if (dp != NULL)
+		closedir(dp);
+	free(tmp);
+	free(realp);
+	return (path);
 }
 
 /*
@@ -4436,7 +4427,7 @@ zfs_dev_is_dm(char *dev_name)
 
 	char *tmp;
 	tmp = dm_get_underlying_path(dev_name);
-	if (!tmp)
+	if (tmp == NULL)
 		return (0);
 
 	free(tmp);
@@ -4489,17 +4480,17 @@ zfs_get_underlying_path(char *dev_name)
 	char *name = NULL;
 	char *tmp;
 
-	if (!dev_name)
+	if (dev_name == NULL)
 		return (NULL);
 
 	tmp = dm_get_underlying_path(dev_name);
 
 	/* dev_name not a DM device, so just un-symlinkize it */
-	if (!tmp)
+	if (tmp == NULL)
 		tmp = realpath(dev_name, NULL);
 
-	if (tmp) {
-		name = zfs_strip_partition(tmp);
+	if (tmp != NULL) {
+		name = zfs_strip_partition_path(tmp);
 		free(tmp);
 	}
 
@@ -4532,12 +4523,12 @@ zfs_get_enclosure_sysfs_path(char *dev_name)
 	size_t size;
 	int tmpsize;
 
-	if (!dev_name)
+	if (dev_name == NULL)
 		return (NULL);
 
 	/* If they preface 'dev' with a path (like "/dev") then strip it off */
 	tmp1 = strrchr(dev_name, '/');
-	if (tmp1)
+	if (tmp1 != NULL)
 		dev_name = tmp1 + 1;    /* +1 since we want the chr after '/' */
 
 	tmpsize = asprintf(&tmp1, "/sys/block/%s/device", dev_name);
@@ -4558,7 +4549,7 @@ zfs_get_enclosure_sysfs_path(char *dev_name)
 	 */
 	while ((ep = readdir(dp))) {
 		/* Ignore everything that's not our enclosure_device link */
-		if (!strstr(ep->d_name, "enclosure_device"))
+		if (strstr(ep->d_name, "enclosure_device") == NULL)
 			continue;
 
 		if (asprintf(&tmp2, "%s/%s", tmp1, ep->d_name) == -1 ||
@@ -4605,7 +4596,7 @@ end:
 	free(tmp2);
 	free(tmp1);
 
-	if (dp)
+	if (dp != NULL)
 		closedir(dp);
 
 	return (path);