macOS: improve handling of invariant disks

Don't prepend /dev to all paths not starting with
/dev as InvariantDisks places its symlinks in
/var/run/disk/by-* not /dev/disk/by-*.

Also, merge in some tweaks from Linux's
zpool_vdev_os.c such as only using O_EXCL with
spares.

Author: ilovezfs

cmd/zpool/os/macos/zpool_vdev_os.c

@@ -88,25 +88,41 @@ check_slice(const char *path, int force, boolean_t isspare)
 	return (0);
 }
 
+/*
+ * Validate that a disk including all partitions are safe to use.
+ *
+ * For EFI labeled disks this can done relatively easily with the libefi
+ * library.  The partition numbers are extracted from the label and used
+ * to generate the expected /dev/ paths.  Each partition can then be
+ * checked for conflicts.
+ *
+ * For non-EFI labeled disks (MBR/EBR/etc) the same process is possible
+ * but due to the lack of a readily available libraries this scanning is
+ * not implemented.  Instead only the device path as given is checked.
+ */
 static int
 check_disk(const char *path, int force,
     boolean_t isspare, boolean_t iswholedisk)
 {
 	struct dk_gpt *vtoc;
 	char slice_path[MAXPATHLEN];
 	int err = 0;
-	int slice_err = 0;
 	int fd, i;
+	int flags = O_RDONLY|O_DIRECT;
 
 	if (!iswholedisk)
 		return (check_slice(path, force, isspare));
 
-	if ((fd = open(path, O_RDONLY|O_DIRECT)) < 0) {
-		check_error(errno);
+	/* only spares can be shared, other devices require exclusive access */
+	if (!isspare)
+		flags |= O_EXCL;
+
+	if ((fd = open(path, flags)) < 0) {
 		return (-1);
 	}
+
 	/*
-	 * Expected to fail for non-EFI labled disks.  Just check the device
+	 * Expected to fail for non-EFI labeled disks.  Just check the device
 	 * as given and do not attempt to detect and scan partitions.
 	 */
 	err = efi_alloc_and_read(fd, &vtoc);
@@ -125,25 +141,25 @@ check_disk(const char *path, int force,
 		(void) close(fd);
 
 		if (force) {
-			/* Partitions will no be created using the backup */
+			/* Partitions will now be created using the backup */
 			return (0);
 		} else {
 			vdev_error(gettext("%s contains a corrupt primary "
 			    "EFI label.\n"), path);
 			return (-1);
 		}
 	}
+
 	for (i = 0; i < vtoc->efi_nparts; i++) {
 		if (vtoc->efi_parts[i].p_tag == V_UNASSIGNED ||
 		    uuid_is_null((uchar_t *)&vtoc->efi_parts[i].p_guid))
 			continue;
 		(void) snprintf(slice_path, sizeof (slice_path),
 		    "%ss%d", path, i+1);
-		slice_err = check_slice(slice_path, force, isspare);
 
-		// Latch the first error that occurs
-		if (err == 0)
-			err = slice_err;
+		err = check_slice(slice_path, force, isspare);
+		if (err)
+			break;
 	}
 
 	efi_free(vtoc);
@@ -152,19 +168,12 @@ check_disk(const char *path, int force,
 	return (err);
 }
 
-
 int
-check_device(const char *name, boolean_t force,
+check_device(const char *path, boolean_t force,
     boolean_t isspare, boolean_t iswholedisk)
 {
-	char path[MAXPATHLEN];
 	int error;
 
-	if (strncmp(name, _PATH_DEV, sizeof (_PATH_DEV) - 1) != 0)
-		snprintf(path, sizeof (path), "%s%s", _PATH_DEV, name);
-	else
-		strlcpy(path, name, sizeof (path));
-
 	error = check_disk(path, force, isspare, iswholedisk);
 	if (error != 0)
 		return (error);

lib/libzutil/os/macos/zutil_device_path_os.c

@@ -31,10 +31,6 @@
 
 #include <libzutil.h>
 
-/*
- * We don't strip/append partitions on FreeBSD.
- */
-
 /*
  * Note: The caller must free the returned string.
  */
@@ -43,6 +39,7 @@ zfs_strip_partition(char *dev)
 {
 	unsigned int disk, slice;
 	char *partless;
+	char whole_disk[MAXPATHLEN];
 
 	partless = strdup(dev);
 
@@ -52,6 +49,16 @@ zfs_strip_partition(char *dev)
 		r = strrchr(partless, 's');
 		if (r != NULL)
 			*r = 0;
+	} else if ((sscanf(partless, "%[^:]:%u", whole_disk, &slice)) == 2) {
+		char *r;
+		r = strrchr(partless, ':');
+		if (r != NULL) {
+			if (strchr(partless, '@')) { // by-path
+				if (slice == 1)
+					r[1] = '0';
+			} else // by-serial
+				*r = 0;
+		}
 	}
 
 	return (partless);
@@ -61,23 +68,29 @@ int
 zfs_append_partition(char *path, size_t max_len)
 {
 	int len = strlen(path);
+	char dpath[max_len];
+	if (strncmp(path, "/var/", 5) == 0) {
+		(void) strlcpy(dpath, "/private", max_len);
+		(void) strlcat(dpath, path, max_len);
+	} else
+		strlcpy(dpath, path, max_len);
 
-	if (strncmp(path, "/private/var/run/disk/by-id", 27) == 0) {
+
+	if (strncmp(dpath, "/private/var/run/disk/by-id", 27) == 0) {
 		return (len);
-	} else if (strncmp(path, "/private/var/run/disk/by-path", 29) == 0) {
+	} else if (strncmp(dpath, "/private/var/run/disk/by-path", 29) == 0) {
 		if (path[len - 1] == '0' &&
 		    path[len - 2] == ':')
 			path[len - 1] = '1';
-		else
-			return (-1); /* should have ended with ":0" */
 
-	} else if (strncmp(path, "/private/var/run/disk/by-serial", 31) == 0) {
+	} else if (strncmp(dpath, "/private/var/run/disk/by-serial", 31) == 0) {
 		if (len + 2 >= max_len)
 			return (-1);
 
-		(void) strcat(path, ":1");
-		len += 2;
-
+		if (strchr(path, ':') == NULL) {
+			(void) strcat(path, ":1");
+			len += 2;
+		}
 	} else {
 
 		if (len + 2 >= max_len)