From 6aae7985eb8ecb6faecb20376500f1026960a801 Mon Sep 17 00:00:00 2001
From: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Date: Mon, 4 Mar 2024 12:20:19 -0500
Subject: [PATCH] fall back to user ioctl for ino path lookup

---
 cmds/receive.c        |  2 +-
 cmds/subvolume-list.c | 48 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/cmds/receive.c b/cmds/receive.c
index e4430b07..051eca6a 100644
--- a/cmds/receive.c
+++ b/cmds/receive.c
@@ -1285,7 +1285,7 @@ static int process_encoded_write(const char *path, const void *data, u64 offset,
 		if (ret >= 0)
 			return 0;
 		/* Fall back for these errors, fail hard for anything else. */
-		if (errno != ENOSPC && errno != ENOTTY && errno != EINVAL) {
+		if (errno != ENOSPC && errno != ENOTTY && errno != EINVAL && errno != EPERM) {
 			ret = -errno;
 			error("encoded_write: writing to %s failed: %m", path);
 			return ret;
diff --git a/cmds/subvolume-list.c b/cmds/subvolume-list.c
index 5a91f41d..c3bc7b70 100644
--- a/cmds/subvolume-list.c
+++ b/cmds/subvolume-list.c
@@ -759,6 +759,49 @@ static int resolve_root(struct rb_root *rl, struct root_info *ri,
 	return 0;
 }
 
+/*
+ * as user, for a single root_info, ask the kernel to give us a path name
+ * inside it's ref_root for the dir_id where it lives.
+ *
+ * This fills in root_info->path with the path to the directory and and
+ * appends this root's name.
+ */
+static int lookup_ino_path_user(int fd, struct root_info *ri)
+{
+	struct btrfs_ioctl_ino_lookup_user_args args;
+	int ret;
+
+	if (ri->path)
+		return 0;
+
+	if (!ri->ref_tree)
+		return -ENOENT;
+
+	memset(&args, 0, sizeof(args));
+	args.treeid = ri->ref_tree;
+	args.dirid = ri->dir_id;
+
+	ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP_USER, &args);
+	if (ret < 0) {
+		if (errno == ENOENT) {
+			ri->ref_tree = 0;
+			return -ENOENT;
+		}
+		error("failed to lookup path for root %llu: %m", ri->ref_tree);
+		return ret;
+	}
+
+	ri->path = malloc(strlen(args.name) + strlen(args.path) + 1);
+	if (!ri->path) {
+		error_msg(ERROR_MSG_MEMORY, NULL);
+		exit(1);
+	}
+
+	strcpy(ri->path, args.path);
+	strcat(ri->path, args.name);
+	return 0;
+}
+
 /*
  * for a single root_info, ask the kernel to give us a path name
  * inside it's ref_root for the dir_id where it lives.
@@ -783,6 +826,11 @@ static int lookup_ino_path(int fd, struct root_info *ri)
 
 	ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &args);
 	if (ret < 0) {
+		if (errno == EPERM) {
+			/* Let's try again with the user ioctl */
+			return lookup_ino_path_user(fd, ri);
+		}
+
 		if (errno == ENOENT) {
 			ri->ref_tree = 0;
 			return -ENOENT;
-- 
2.44.0