Turn on/off enclosure slot fault LED even when disk isn't present

Previously when a drive faulted, the statechange-led.sh script would lookup
the drive's LED sysfs entry in /sys/block/sd*/device/enclosure_device, and
turn it on.  During testing we noticed that if you pulled out a drive, or if
the drive was so badly broken that it no longer appeared to Linux, that the
/sys/block/sd* path would be removed, and the script could not lookup the
LED entry.

To fix this, this patch looks up the disks's more persistent
"/sys/class/enclosure/X:X:X:X/Slot N" LED sysfs path at pool import.  It then
passes that path to the statechange-led script to use, rather than having the
script look it up on the fly.  This allows the script to turn on/off the slot
LEDs even when the drive is missing.

Closes #5309 
Closes #2375

lib/libzfs/libzfs_import.c

@@ -64,6 +64,7 @@
 #include <blkid/blkid.h>
 #include "libzfs.h"
 #include "libzfs_impl.h"
+#include <libzfs.h>
 
 /*
  * Intermediate structures used to gather configuration information.
@@ -437,6 +438,10 @@ no_dev:
  *
  * multipath device node example:
  * 	devid:		'dm-uuid-mpath-35000c5006304de3f'
+ *
+ * We also store the enclosure sysfs path for turning on enclosure LEDs
+ * (if applicable):
+ *	vdev_enc_sysfs_path: '/sys/class/enclosure/11:0:1:0/SLOT 4'
  */
 void
 update_vdev_config_dev_strs(nvlist_t *nv)
@@ -444,6 +449,7 @@ update_vdev_config_dev_strs(nvlist_t *nv)
 	vdev_dev_strs_t vds;
 	char *env, *type, *path;
 	uint64_t wholedisk = 0;
+	char *upath, *spath;
 
 	/*
 	 * For the benefit of legacy ZFS implementations, allow
@@ -470,6 +476,7 @@ update_vdev_config_dev_strs(nvlist_t *nv)
 	    !strncasecmp(env, "YES", 3) || !strncasecmp(env, "ON", 2))) {
 		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_DEVID);
 		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_PHYS_PATH);
+		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH);
 		return;
 	}
 
@@ -490,10 +497,20 @@ update_vdev_config_dev_strs(nvlist_t *nv)
 			(void) nvlist_add_string(nv, ZPOOL_CONFIG_PHYS_PATH,
 			    vds.vds_devphys);
 		}
+
+		/* Add enclosure sysfs path (if disk is in an enclosure) */
+		upath = zfs_get_underlying_path(path);
+		spath = zfs_get_enclosure_sysfs_path(upath);
+		if (spath)
+			nvlist_add_string(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH,
+			    spath);
+		free(upath);
+		free(spath);
 	} else {
 		/* clear out any stale entries */
 		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_DEVID);
 		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_PHYS_PATH);
+		(void) nvlist_remove_all(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH);
 	}
 }
 #else

lib/libzfs/libzfs_pool.c

@@ -4407,7 +4407,7 @@ static char * dm_get_underlying_path(char *dm_name)
 		goto end;
 
 	if ((asprintf(&tmp, "/dev/block/%d:%d", child_info->major,
-	    child_info->minor) == -1) || !tmp)
+	    child_info->minor) == -1) || tmp == NULL)
 		goto end;
 
 	/* Further translate /dev/block/ name into the normal name */
@@ -4430,11 +4430,11 @@ end:
  * Return 0 if not.
  */
 int
-dev_is_dm(char *devname)
+zfs_dev_is_dm(char *dev_name)
 {
 
 	char *tmp;
-	tmp = dm_get_underlying_path(devname);
+	tmp = dm_get_underlying_path(dev_name);
 	if (!tmp)
 		return (0);
 
@@ -4483,7 +4483,7 @@ dev_is_dm(char *devname)
  * NOTE: The returned name string must be *freed*.
  */
 char *
-get_underlying_path(libzfs_handle_t *hdl, char *dev_name)
+zfs_get_underlying_path(char *dev_name)
 {
 	char *name = NULL;
 	char *tmp;
@@ -4504,3 +4504,108 @@ get_underlying_path(libzfs_handle_t *hdl, char *dev_name)
 
 	return (name);
 }
+
+/*
+ * Given a dev name like "sda", return the full enclosure sysfs path to
+ * the disk.  You can also pass in the name with "/dev" prepended
+ * to it (like /dev/sda).
+ *
+ * For example, disk "sda" in enclosure slot 1:
+ *     dev:            "sda"
+ *     returns:        "/sys/class/enclosure/1:0:3:0/Slot 1"
+ *
+ * 'dev' must be a non-devicemapper device.
+ *
+ * Returned string must be freed.
+ */
+char *
+zfs_get_enclosure_sysfs_path(char *dev_name)
+{
+	DIR *dp = NULL;
+	struct dirent *ep;
+	char buf[MAXPATHLEN];
+	char *tmp1 = NULL;
+	char *tmp2 = NULL;
+	char *tmp3 = NULL;
+	char *path = NULL;
+	size_t size;
+	int tmpsize;
+
+	if (!dev_name)
+		return (NULL);
+
+	/* If they preface 'dev' with a path (like "/dev") then strip it off */
+	tmp1 = strrchr(dev_name, '/');
+	if (tmp1)
+		dev_name = tmp1 + 1;    /* +1 since we want the chr after '/' */
+
+	tmpsize = asprintf(&tmp1, "/sys/block/%s/device", dev_name);
+	if (tmpsize == -1 || tmp1 == NULL) {
+		tmp1 = NULL;
+		goto end;
+	}
+
+	dp = opendir(tmp1);
+	if (dp == NULL) {
+		tmp1 = NULL;	/* To make free() at the end a NOP */
+		goto end;
+	}
+
+	/*
+	 * Look though all sysfs entries in /sys/block/<dev>/device for
+	 * the enclosure symlink.
+	 */
+	while ((ep = readdir(dp))) {
+		/* Ignore everything that's not our enclosure_device link */
+		if (!strstr(ep->d_name, "enclosure_device"))
+			continue;
+
+		if (asprintf(&tmp2, "%s/%s", tmp1, ep->d_name) == -1 ||
+		    tmp2 == NULL)
+			break;
+
+		size = readlink(tmp2, buf, sizeof (buf));
+
+		/* Did readlink fail or crop the link name? */
+		if (size == -1 || size >= sizeof (buf)) {
+			free(tmp2);
+			tmp2 = NULL;	/* To make free() at the end a NOP */
+			break;
+		}
+
+		/*
+		 * We got a valid link.  readlink() doesn't terminate strings
+		 * so we have to do it.
+		 */
+		buf[size] = '\0';
+
+		/*
+		 * Our link will look like:
+		 *
+		 * "../../../../port-11:1:2/..STUFF../enclosure/1:0:3:0/SLOT 1"
+		 *
+		 * We want to grab the "enclosure/1:0:3:0/SLOT 1" part
+		 */
+		tmp3 = strstr(buf, "enclosure");
+		if (tmp3 == NULL)
+			break;
+
+		if (asprintf(&path, "/sys/class/%s", tmp3) == -1) {
+			/* If asprintf() fails, 'path' is undefined */
+			path = NULL;
+			break;
+		}
+
+		if (path == NULL)
+			break;
+	}
+
+end:
+	free(tmp2);
+	free(tmp1);
+
+	if (dp)
+		closedir(dp);
+
+	return (path);
+}