[PATCH 0/3] Btrfs-progs: fix 'subvol get-default' command

[PATCH 0/3] Btrfs-progs: fix 'subvol get-default' command

[Ilya Dryomov]

'btrfs subvol get-default' has been broken for a while, fix it.  Patches
1 and 2 are straightforward cleanups in that area, patch 3 fixes the
problem.

Thanks,

		Ilya


Ilya Dryomov (3):
  Btrfs-progs: nuke redundant zeroing in __list_subvol_search()
  Btrfs-progs: refactor resolve_root() function a bit
  Btrfs-progs: bring 'subvol get-default' back in

 btrfs-list.c |  106 +++++++++++++++++++++++++++++++++++++++++++++++++---------
 ctree.h      |    2 +
 2 files changed, 92 insertions(+), 16 deletions(-)

-- 
1.7.9.1

[PATCH 1/3] Btrfs-progs: nuke redundant zeroing in __list_subvol_search()

[Ilya Dryomov]

There's no need to zero out things twice.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 btrfs-list.c |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/btrfs-list.c b/btrfs-list.c
index 5f4a9be..44a73de 100644
--- a/btrfs-list.c
+++ b/btrfs-list.c
@@ -569,10 +569,6 @@ static int __list_subvol_search(int fd, struct root_lookup *root_lookup)
 	root_lookup_init(root_lookup);
 	memset(&args, 0, sizeof(args));
 
-	root_lookup_init(root_lookup);
-
-	memset(&args, 0, sizeof(args));
-
 	/* search in the tree of tree roots */
 	sk->tree_id = 1;
 
-- 
1.7.9.1

[PATCH 2/3] Btrfs-progs: refactor resolve_root() function a bit

[Ilya Dryomov]

Don't pass a pointer to root_id to resolve_root().  It's always the same as
ri->root_id, passing a pointer hints that root_id can somehow change which is
not true.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 btrfs-list.c |   21 ++++++++++-----------
 1 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/btrfs-list.c b/btrfs-list.c
index 44a73de..cc1dc66 100644
--- a/btrfs-list.c
+++ b/btrfs-list.c
@@ -200,7 +200,7 @@ static int add_root(struct root_lookup *root_lookup,
  * in by lookup_ino_path
  */
 static int resolve_root(struct root_lookup *rl, struct root_info *ri,
-			u64 *root_id, u64 *parent_id, u64 *top_id, char **path)
+			u64 *parent_id, u64 *top_id, char **path)
 {
 	char *full_path = NULL;
 	int len = 0;
@@ -254,7 +254,6 @@ static int resolve_root(struct root_lookup *rl, struct root_info *ri,
 		}
 	}
 
-	*root_id = ri->root_id;
 	*path = full_path;
 
 	return 0;
@@ -692,23 +691,23 @@ int list_subvols(int fd, int print_parent)
 	n = rb_last(&root_lookup.root);
 	while (n) {
 		struct root_info *entry;
-		u64 root_id;
 		u64 level;
 		u64 parent_id;
 		char *path;
+
 		entry = rb_entry(n, struct root_info, rb_node);
-		resolve_root(&root_lookup, entry, &root_id, &parent_id,
-				&level, &path);
+		resolve_root(&root_lookup, entry, &parent_id, &level, &path);
 		if (print_parent) {
 			printf("ID %llu parent %llu top level %llu path %s\n",
-				(unsigned long long)root_id,
+				(unsigned long long)entry->root_id,
 				(unsigned long long)parent_id,
 				(unsigned long long)level, path);
 		} else {
 			printf("ID %llu top level %llu path %s\n",
-				(unsigned long long)root_id,
+				(unsigned long long)entry->root_id,
 				(unsigned long long)level, path);
 		}
+
 		free(path);
 		n = rb_prev(n);
 	}
@@ -914,17 +913,17 @@ char *path_for_root(int fd, u64 root)
 	n = rb_last(&root_lookup.root);
 	while (n) {
 		struct root_info *entry;
-		u64 root_id;
 		u64 parent_id;
 		u64 level;
 		char *path;
+
 		entry = rb_entry(n, struct root_info, rb_node);
-		resolve_root(&root_lookup, entry, &root_id, &parent_id, &level,
-				&path);
-		if (root_id == root)
+		resolve_root(&root_lookup, entry, &parent_id, &level, &path);
+		if (entry->root_id == root)
 			ret_path = path;
 		else
 			free(path);
+
 		n = rb_prev(n);
 	}
 
-- 
1.7.9.1

[PATCH 3/3] Btrfs-progs: bring 'subvol get-default' back in

[Ilya Dryomov]

Commit bab2c565 accidentally broke 'subvol get-default' command by
removing almost all of the underlying code.  Bring it back with some
fixes and improvements.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 btrfs-list.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 ctree.h      |    2 +
 2 files changed, 82 insertions(+), 1 deletions(-)

diff --git a/btrfs-list.c b/btrfs-list.c
index cc1dc66..00c428b 100644
--- a/btrfs-list.c
+++ b/btrfs-list.c
@@ -552,6 +552,60 @@ build:
 	return full;
 }
 
+static int get_default_subvolid(int fd, u64 *default_id)
+{
+	struct btrfs_ioctl_search_args args;
+	struct btrfs_ioctl_search_key *sk = &args.key;
+	struct btrfs_ioctl_search_header *sh;
+	u64 found = 0;
+	int ret;
+
+	memset(&args, 0, sizeof(args));
+
+	/*
+	 * search for a dir item with a name 'default' in the tree of
+	 * tree roots, it should point us to a default root
+	 */
+	sk->tree_id = 1;
+
+	/* don't worry about ancient format and request only one item */
+	sk->nr_items = 1;
+
+	sk->max_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
+	sk->min_objectid = BTRFS_ROOT_TREE_DIR_OBJECTID;
+	sk->max_type = BTRFS_DIR_ITEM_KEY;
+	sk->min_type = BTRFS_DIR_ITEM_KEY;
+	sk->max_offset = (u64)-1;
+	sk->max_transid = (u64)-1;
+
+	ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
+	if (ret < 0)
+		return ret;
+
+	/* the ioctl returns the number of items it found in nr_items */
+	if (sk->nr_items == 0)
+		goto out;
+
+	sh = (struct btrfs_ioctl_search_header *)args.buf;
+
+	if (sh->type == BTRFS_DIR_ITEM_KEY) {
+		struct btrfs_dir_item *di;
+		int name_len;
+		char *name;
+
+		di = (struct btrfs_dir_item *)(sh + 1);
+		name_len = btrfs_stack_dir_name_len(di);
+		name = (char *)(di + 1);
+
+		if (!strncmp("default", name, name_len))
+			found = btrfs_disk_key_objectid(&di->location);
+	}
+
+out:
+	*default_id = found;
+	return 0;
+}
+
 static int __list_subvol_search(int fd, struct root_lookup *root_lookup)
 {
 	int ret;
@@ -663,12 +717,32 @@ static int __list_subvol_fill_paths(int fd, struct root_lookup *root_lookup)
 	return 0;
 }
 
-int list_subvols(int fd, int print_parent)
+int list_subvols(int fd, int print_parent, int get_default)
 {
 	struct root_lookup root_lookup;
 	struct rb_node *n;
+	u64 default_id;
 	int ret;
 
+	if (get_default) {
+		ret = get_default_subvolid(fd, &default_id);
+		if (ret) {
+			fprintf(stderr, "ERROR: can't perform the search - %s\n",
+				strerror(errno));
+			return ret;
+		}
+		if (default_id == 0) {
+			fprintf(stderr, "ERROR: 'default' dir item not found\n");
+			return ret;
+		}
+
+		/* no need to resolve roots if FS_TREE is default */
+		if (default_id == BTRFS_FS_TREE_OBJECTID) {
+			printf("ID 5 (FS_TREE)\n");
+			return ret;
+		}
+	}
+
 	ret = __list_subvol_search(fd, &root_lookup);
 	if (ret) {
 		fprintf(stderr, "ERROR: can't perform the search - %s\n",
@@ -696,6 +770,11 @@ int list_subvols(int fd, int print_parent)
 		char *path;
 
 		entry = rb_entry(n, struct root_info, rb_node);
+		if (get_default && entry->root_id != default_id) {
+			n = rb_prev(n);
+			continue;
+		}
+
 		resolve_root(&root_lookup, entry, &parent_id, &level, &path);
 		if (print_parent) {
 			printf("ID %llu parent %llu top level %llu path %s\n",
diff --git a/ctree.h b/ctree.h
index 5309059..141ec59 100644
--- a/ctree.h
+++ b/ctree.h
@@ -1416,6 +1416,8 @@ BTRFS_SETGET_FUNCS(dir_type, struct btrfs_dir_item, type, 8);
 BTRFS_SETGET_FUNCS(dir_name_len, struct btrfs_dir_item, name_len, 16);
 BTRFS_SETGET_FUNCS(dir_transid, struct btrfs_dir_item, transid, 64);
 
+BTRFS_SETGET_STACK_FUNCS(stack_dir_name_len, struct btrfs_dir_item, name_len, 16);
+
 static inline void btrfs_dir_item_key(struct extent_buffer *eb,
 				      struct btrfs_dir_item *item,
 				      struct btrfs_disk_key *key)
-- 
1.7.9.1