Allow relative paths for btrfs send

The initial btrfs send code was easily confused by relative paths and by
anything that wasn't in the root of the FS.  This fixes it to take
relative paths.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>

cmds-send.c

@@ -27,6 +27,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/ioctl.h>
+#include <libgen.h>
 
 #include <uuid/uuid.h>
 
@@ -55,12 +56,12 @@ struct btrfs_send {
 int find_mount_root(const char *path, char **mount_root)
 {
 	int ret;
-	char cur[BTRFS_PATH_NAME_MAX];
+	char *cur;
 	char fsid[BTRFS_FSID_SIZE];
 	int fd;
 	struct stat st;
-	int pos;
 	char *tmp;
+	char *dup = NULL;
 
 	struct btrfs_ioctl_fs_info_args args;
 
@@ -89,17 +90,15 @@ int find_mount_root(const char *path, char **mount_root)
 	close(fd);
 	fd = -1;
 
-	strcpy(cur, path);
+	cur = strdup(path);
+
 	while (1) {
-		tmp = strrchr(cur, '/');
+		dup = strdup(cur);
+		tmp = dirname(dup);
+
 		if (!tmp)
 			break;
-		if (tmp == cur)
-			break;
-		pos = tmp - cur;
-		cur[pos] = 0;
-
-		fd = open(cur, O_RDONLY | O_NOATIME);
+		fd = open(tmp, O_RDONLY | O_NOATIME);
 		if (fd < 0) {
 			ret = -errno;
 			goto out;
@@ -108,20 +107,27 @@ int find_mount_root(const char *path, char **mount_root)
 		ret = ioctl(fd, BTRFS_IOC_FS_INFO, &args);
 		close(fd);
 		fd = -1;
-		if (ret < 0) {
-			cur[pos] = '/';
+		if (ret < 0)
 			break;
-		}
-		if (memcmp(fsid, args.fsid, BTRFS_FSID_SIZE) != 0) {
-			cur[pos] = '/';
+		if (memcmp(fsid, args.fsid, BTRFS_FSID_SIZE) != 0)
+			break;
+
+		free(cur);
+		cur = strdup(tmp);
+		free(dup);
+		dup = NULL;
+		if (strcmp(cur, "/") == 0)
+			break;
+		if (strcmp(cur, ".") == 0)
 			break;
-		}
 	}
 
 	ret = 0;
 	*mount_root = realpath(cur, NULL);
 
 out:
+	if (dup)
+		free(dup);
 	if (fd != -1)
 		close(fd);
 	return ret;
@@ -373,7 +379,13 @@ out:
 
 static const char *get_subvol_name(struct btrfs_send *s, const char *full_path)
 {
-	return full_path + strlen(s->root_path) + 1;
+	int len = strlen(s->root_path);
+	if (!len)
+		return full_path;
+	if (s->root_path[len - 1] != '/')
+		len += 1;
+
+	return full_path + len;
 }
 
 static int init_root_path(struct btrfs_send *s, const char *subvol)
@@ -527,6 +539,12 @@ int cmd_send_start(int argc, char **argv)
 	/* use first send subvol to determine mount_root */
 	subvol = argv[optind];
 
+	subvol = realpath(argv[optind], NULL);
+	if (!subvol) {
+		fprintf(stderr, "ERROR: unable to resolve %s\n", argv[optind]);
+		goto out;
+	}
+
 	ret = init_root_path(&send, subvol);
 	if (ret < 0)
 		goto out;
@@ -545,7 +563,11 @@ int cmd_send_start(int argc, char **argv)
 	}
 
 	for (i = optind; i < argc; i++) {
-		subvol = argv[i];
+		subvol = realpath(argv[i], NULL);
+		if (!subvol) {
+			fprintf(stderr, "ERROR: unable to resolve %s\n", argv[i]);
+			goto out;
+		}
 
 		ret = find_mount_root(subvol, &mount_root);
 		if (ret < 0) {
@@ -571,6 +593,7 @@ int cmd_send_start(int argc, char **argv)
 					subvol);
 			goto out;
 		}
+		free(subvol);
 	}
 
 	for (i = optind; i < argc; i++) {

send-utils.c

@@ -268,7 +268,6 @@ int subvol_uuid_search_init(int mnt_fd, struct subvol_uuid_search *s)
 				si->stransid = btrfs_root_stransid(&root_item);
 				si->rtransid = btrfs_root_rtransid(&root_item);
 				si->path = path;
-
 				subvol_uuid_search_add(s, si);
 				root_item_valid = 0;
 			} else {