[PATCH v3 00/10] undelete subvolume offline version

[PATCH v3 00/10] undelete subvolume offline version

[Lu Fengqi]

This patchset will add undelete-subvol subcommand for btrfs rescue.

Patchset can be fetched from github:
https://github.com/littleroad/btrfs-progs.git undelete

v2->v3: fixed some issues pointed out by Qu.
v1->v2: add -s option to allow user specify the subvolume which will be
recovered.

The first patch are not modified.
For the rest, please see the changelog in the patches.

Lu Fengqi (10):
  btrfs-progs: copy btrfs_del_orphan_item from kernel
  btrfs-progs: extract btrfs_link_subvol from btrfs_mksubvol
  btrfs-progs: use btrfs_find_free_dir_index to find free inode index
  btrfs-progs: undelete-subvol: introduce is_subvol_intact
  btrfs-progs: undelete-subvol: introduce recover_dead_root
  btrfs-progs: undelete-subvol: introduce link_subvol_to_lostfound
  btrfs-progs: undelete-subvol: introduce btrfs_undelete_subvols
  btrfs-progs: undelete-subvol: add undelete-subvol subcommand
  btrfs-progs: tests: add testcase for undelete-subvol
  btrfs-progs: undelete-subvol: update completion and documentation

 Documentation/btrfs-rescue.asciidoc           |  12 +
 Makefile                                      |   3 +-
 btrfs-completion                              |   2 +-
 cmds-rescue.c                                 |  69 ++++++
 convert/main.c                                |  59 ++++-
 ctree.h                                       |   8 +-
 inode.c                                       | 119 +++++----
 .../031-undelete-subvol/intact_subvolume.img  | Bin 0 -> 4096 bytes
 .../subvolume_in_drop_progress.raw.xz         | Bin 0 -> 23452 bytes
 tests/misc-tests/031-undelete-subvol/test.sh  |  38 +++
 undelete-subvol.c                             | 227 ++++++++++++++++++
 undelete-subvol.h                             |  11 +
 12 files changed, 501 insertions(+), 47 deletions(-)
 create mode 100644 tests/misc-tests/031-undelete-subvol/intact_subvolume.img
 create mode 100644 tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz
 create mode 100755 tests/misc-tests/031-undelete-subvol/test.sh
 create mode 100644 undelete-subvol.c
 create mode 100644 undelete-subvol.h

-- 
2.17.0

[PATCH v3 01/10] btrfs-progs: copy btrfs_del_orphan_item from kernel

[Lu Fengqi]

Add btrfs_del_orphan_item for the later subvolume undelete.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
 ctree.h |  2 ++
 inode.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/ctree.h b/ctree.h
index 1fef37c93485..46a1dbfd2f27 100644
--- a/ctree.h
+++ b/ctree.h
@@ -2796,6 +2796,8 @@ int btrfs_unlink(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 int btrfs_add_orphan_item(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, struct btrfs_path *path,
 			  u64 ino);
+int btrfs_del_orphan_item(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root, u64 offset);
 int btrfs_mkdir(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		char *name, int namelen, u64 parent_ino, u64 *ino, int mode);
 struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root, const char *base,
diff --git a/inode.c b/inode.c
index 2398bca4a109..8d0812c7cf50 100644
--- a/inode.c
+++ b/inode.c
@@ -262,6 +262,36 @@ int btrfs_add_orphan_item(struct btrfs_trans_handle *trans,
 	return btrfs_insert_empty_item(trans, root, path, &key, 0);
 }
 
+int btrfs_del_orphan_item(struct btrfs_trans_handle *trans,
+			  struct btrfs_root *root, u64 offset)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	int ret = 0;
+
+	key.objectid = BTRFS_ORPHAN_OBJECTID;
+	key.type = BTRFS_ORPHAN_ITEM_KEY;
+	key.offset = offset;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = btrfs_del_item(trans, root, path);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
 /*
  * Unlink an inode, which will remove its backref and corresponding dir_index/
  * dir_item if any of them exists.
-- 
2.17.0

[PATCH v3 02/10] btrfs-progs: extract btrfs_link_subvol from btrfs_mksubvol

[Lu Fengqi]

The original btrfs_mksubvol is too specific to specify the directory that
the subvolume will link to. Furthermore, in this transaction, we don't only
need to create root_ref/dir-item, but also update the flags of root_item.
Extract a generic btrfs_link_subvol that allow the caller pass a trans
argument for later subvolume undelete. And rename the original
btrfs_mksubvol to link_subvol_for_convert since it is a less generic
btrfs_link_subvol.

No functional changes.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3:
rename the btrfs_mksubvol to link_subvol_for_convert;
remove the redundant parameter convert from link_subvol_for_convert;
rename convert to resolve_conflict in btrfs_link_subvol;
set root refs to 1 in btrfs_link_subvol.

 convert/main.c | 59 ++++++++++++++++++++++++++++++++++++++++++--
 ctree.h        |  5 ++--
 inode.c        | 66 ++++++++++++++++++++++++++++++++------------------
 3 files changed, 103 insertions(+), 27 deletions(-)

diff --git a/convert/main.c b/convert/main.c
index 80f3bed84c84..b092e25bccbb 100644
--- a/convert/main.c
+++ b/convert/main.c
@@ -1002,6 +1002,61 @@ err:
 	return ret;
 }
 
+/*
+ * Link the subvolume specified by @root_objectid to the root_dir of @root.
+ *
+ * @root		the root of the file tree which the subvolume will
+ *			be linked to.
+ * @subvol_name		the name of the subvolume which will be named.
+ * @root_objectid	specify the subvolume which will be linked.
+ *
+ * Return the root of the subvolume if success, otherwise return NULL.
+ */
+static struct btrfs_root *link_subvol_for_convert(struct btrfs_root *root,
+						  const char *subvol_name,
+						  u64 root_objectid)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *subvol_root = NULL;
+	struct btrfs_key key;
+	u64 dirid = btrfs_root_dirid(&root->root_item);
+	int ret;
+
+	/*
+	 * 2 for dir's dir_index and dir_item for the subvolume
+	 * 2 for the subvolume's root_ref and root_backref
+	 */
+	trans = btrfs_start_transaction(root, 4);
+	if (IS_ERR(trans)) {
+		error("unable to start transaction");
+		goto fail;
+	}
+
+	ret = btrfs_link_subvol(trans, root, subvol_name, root_objectid, dirid,
+				true);
+	if (ret) {
+		error("unable to link subvolume %s", subvol_name);
+		goto fail;
+	}
+
+	ret = btrfs_commit_transaction(trans, root);
+	if (ret) {
+		error("transaction commit failed: %d", ret);
+		goto fail;
+	}
+
+	key.objectid = root_objectid;
+	key.offset = (u64)-1;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+
+	subvol_root = btrfs_read_fs_root(root->fs_info, &key);
+	if (!subvol_root)
+		error("unable to link subvolume %s", subvol_name);
+
+fail:
+	return subvol_root;
+}
+
 /*
  * Migrate super block to its default position and zero 0 ~ 16k
  */
@@ -1194,8 +1249,8 @@ static int do_convert(const char *devname, u32 convert_flags, u32 nodesize,
 		task_deinit(ctx.info);
 	}
 
-	image_root = btrfs_mksubvol(root, subvol_name,
-				    CONV_IMAGE_SUBVOL_OBJECTID, true);
+	image_root = link_subvol_for_convert(root, subvol_name,
+					     CONV_IMAGE_SUBVOL_OBJECTID);
 	if (!image_root) {
 		error("unable to link subvolume %s", subvol_name);
 		goto fail;
diff --git a/ctree.h b/ctree.h
index 46a1dbfd2f27..2ac1eb532986 100644
--- a/ctree.h
+++ b/ctree.h
@@ -2800,8 +2800,9 @@ int btrfs_del_orphan_item(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, u64 offset);
 int btrfs_mkdir(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		char *name, int namelen, u64 parent_ino, u64 *ino, int mode);
-struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root, const char *base,
-				  u64 root_objectid, bool convert);
+int btrfs_link_subvol(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		      const char *base, u64 root_objectid, u64 dirid,
+		      bool resolve_conflict);
 
 /* file.c */
 int btrfs_get_extent(struct btrfs_trans_handle *trans,
diff --git a/inode.c b/inode.c
index 8d0812c7cf50..f9b72533f3a9 100644
--- a/inode.c
+++ b/inode.c
@@ -606,20 +606,31 @@ out:
 	return ret;
 }
 
-struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root,
-				  const char *base, u64 root_objectid,
-				  bool convert)
+/*
+ * Link the subvolume specified by @root_objectid to the directory specified by
+ * @dirid on the file tree specified by @root.
+ *
+ * @root		the root of the file tree where the directory on.
+ * @base		the name of the subvolume which will be linked.
+ * @root_objectid	specify the subvolume which will be linked.
+ * @dirid		specify the directory which the subvolume will be
+ *			linked to.
+ * @resolve_conflict	the flag to determine whether to try to resolve
+ *			the name conflict.
+ */
+int btrfs_link_subvol(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		      const char *base, u64 root_objectid, u64 dirid,
+		      bool resolve_conflict)
 {
-	struct btrfs_trans_handle *trans;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_root *tree_root = fs_info->tree_root;
-	struct btrfs_root *new_root = NULL;
 	struct btrfs_path path;
 	struct btrfs_inode_item *inode_item;
+	struct btrfs_root_item root_item;
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
-	u64 dirid = btrfs_root_dirid(&root->root_item);
 	u64 index = 2;
+	u64 offset;
 	char buf[BTRFS_NAME_LEN + 1]; /* for snprintf null */
 	int len;
 	int i;
@@ -627,8 +638,9 @@ struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root,
 
 	len = strlen(base);
 	if (len == 0 || len > BTRFS_NAME_LEN)
-		return NULL;
+		return -EINVAL;
 
+	/* find the free dir_index */
 	btrfs_init_path(&path);
 	key.objectid = dirid;
 	key.type = BTRFS_DIR_INDEX_KEY;
@@ -649,12 +661,7 @@ struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root,
 	}
 	btrfs_release_path(&path);
 
-	trans = btrfs_start_transaction(root, 1);
-	if (IS_ERR(trans)) {
-		error("unable to start transaction");
-		goto fail;
-	}
-
+	/* add the dir_item/dir_index */
 	key.objectid = dirid;
 	key.offset = 0;
 	key.type =  BTRFS_INODE_ITEM_KEY;
@@ -674,7 +681,8 @@ struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root,
 	key.type = BTRFS_ROOT_ITEM_KEY;
 
 	memcpy(buf, base, len);
-	if (convert) {
+	if (resolve_conflict) {
+		/* try to resolve name conflict by adding the number suffix */
 		for (i = 0; i < 1024; i++) {
 			ret = btrfs_insert_dir_item(trans, root, buf, len,
 					dirid, &key, BTRFS_FT_DIR, index);
@@ -719,18 +727,30 @@ struct btrfs_root *btrfs_mksubvol(struct btrfs_root *root,
 		goto fail;
 	}
 
-	ret = btrfs_commit_transaction(trans, root);
+
+	/* set root refs of the subvolume to 1 */
+	key.objectid = root_objectid;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(trans, tree_root, &key, &path, 0, 0);
 	if (ret) {
-		error("transaction commit failed: %d", ret);
+		error("couldn't find ROOT_ITEM for %llu failed: %d",
+				root_objectid, ret);
 		goto fail;
 	}
 
-	new_root = btrfs_read_fs_root(fs_info, &key);
-	if (IS_ERR(new_root)) {
-		error("unable to fs read root: %lu", PTR_ERR(new_root));
-		new_root = NULL;
-	}
+	leaf = path.nodes[0];
+
+	offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
+	read_extent_buffer(leaf, &root_item, offset, sizeof(root_item));
+
+	btrfs_set_root_refs(&root_item, 1);
+
+	write_extent_buffer(leaf, &root_item, offset, sizeof(root_item));
+	btrfs_mark_buffer_dirty(leaf);
+
 fail:
-	btrfs_init_path(&path);
-	return new_root;
+	btrfs_release_path(&path);
+	return ret;
 }
-- 
2.17.0

[PATCH v3 03/10] btrfs-progs: use btrfs_find_free_dir_index to find free inode index

[Lu Fengqi]

Since we have an existing function to find free inode index, we can
reuse it here.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
---
V3: add Reviewed-by from Qu Wenruo.

 inode.c | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/inode.c b/inode.c
index f9b72533f3a9..03b8be63eb0a 100644
--- a/inode.c
+++ b/inode.c
@@ -629,7 +629,7 @@ int btrfs_link_subvol(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	struct btrfs_root_item root_item;
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
-	u64 index = 2;
+	u64 index;
 	u64 offset;
 	char buf[BTRFS_NAME_LEN + 1]; /* for snprintf null */
 	int len;
@@ -640,28 +640,15 @@ int btrfs_link_subvol(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	if (len == 0 || len > BTRFS_NAME_LEN)
 		return -EINVAL;
 
-	/* find the free dir_index */
-	btrfs_init_path(&path);
-	key.objectid = dirid;
-	key.type = BTRFS_DIR_INDEX_KEY;
-	key.offset = (u64)-1;
-
-	ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
-	if (ret <= 0) {
-		error("search for DIR_INDEX dirid %llu failed: %d",
-				(unsigned long long)dirid, ret);
+	/* add the dir_item/dir_index */
+	ret = btrfs_find_free_dir_index(root, dirid, &index);
+	if (ret < 0) {
+		error("unable to find free dir index dirid %llu failed: %d",
+		      (unsigned long long)dirid, ret);
 		goto fail;
 	}
 
-	if (path.slots[0] > 0) {
-		path.slots[0]--;
-		btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
-		if (key.objectid == dirid && key.type == BTRFS_DIR_INDEX_KEY)
-			index = key.offset + 1;
-	}
-	btrfs_release_path(&path);
-
-	/* add the dir_item/dir_index */
+	btrfs_init_path(&path);
 	key.objectid = dirid;
 	key.offset = 0;
 	key.type =  BTRFS_INODE_ITEM_KEY;
-- 
2.17.0

[PATCH v3 04/10] btrfs-progs: undelete-subvol: introduce is_subvol_intact

[Lu Fengqi]

The function is used to determine whether the subvolume is intact.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3:
add SPDX-License-Identifier;
pass btrfs_fs_info instead of btrfs_root;
use btrfs_read_fs_root instead of manually search;
remove empty header file.

 Makefile          |  3 ++-
 undelete-subvol.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 undelete-subvol.c

diff --git a/Makefile b/Makefile
index cbd855336b2f..6a425e3a65dd 100644
--- a/Makefile
+++ b/Makefile
@@ -116,7 +116,8 @@ objects = ctree.o disk-io.o kernel-lib/radix-tree.o extent-tree.o print-tree.o \
 	  qgroup.o free-space-cache.o kernel-lib/list_sort.o props.o \
 	  kernel-shared/ulist.o qgroup-verify.o backref.o string-table.o task-utils.o \
 	  inode.o file.o find-root.o free-space-tree.o help.o send-dump.o \
-	  fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o
+	  fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o \
+	  undelete-subvol.o
 cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
 	       cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
 	       cmds-quota.o cmds-qgroup.o cmds-replace.o check/main.o \
diff --git a/undelete-subvol.c b/undelete-subvol.c
new file mode 100644
index 000000000000..26e156092011
--- /dev/null
+++ b/undelete-subvol.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Fujitsu.  All rights reserved.
+ */
+
+#include "ctree.h"
+#include "disk-io.h"
+
+/*
+ * Determines whether the subvolume is intact, according to the drop_progress
+ * of the root item specified by @subvol_id.
+ *
+ * Return true if the subvolume is intact, otherwise return false.
+ */
+static bool is_subvol_intact(struct btrfs_fs_info *fs_info, u64 subvol_id)
+{
+	struct btrfs_key key;
+	struct btrfs_root *root;
+
+	key.objectid = subvol_id;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = -1;
+
+	root = btrfs_read_fs_root(fs_info, &key);
+	if (IS_ERR(root))
+		return false;
+
+	/* the subvolume is intact if the objectid of drop_progress == 0 */
+	return !btrfs_disk_key_objectid(&root->root_item.drop_progress);
+}
-- 
2.17.0

[PATCH v3 05/10] btrfs-progs: undelete-subvol: introduce recover_dead_root

[Lu Fengqi]

The function will find the root_item specified by the subvol_id
and clear the BTRFS_ROOT_SUBVOL_DEAD flag.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3:
remove btrfs_root argument;
don't modify root_refs.

 ctree.h           |  1 +
 undelete-subvol.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/ctree.h b/ctree.h
index 2ac1eb532986..6e2046145f7c 100644
--- a/ctree.h
+++ b/ctree.h
@@ -186,6 +186,7 @@ static int btrfs_csum_sizes[] = { 4 };
 #define BTRFS_FT_MAX		9
 
 #define BTRFS_ROOT_SUBVOL_RDONLY	(1ULL << 0)
+#define BTRFS_ROOT_SUBVOL_DEAD		(1ULL << 48)
 
 /*
  * the key defines the order in the tree, and so it also defines (optimal)
diff --git a/undelete-subvol.c b/undelete-subvol.c
index 26e156092011..6d3ef19977d6 100644
--- a/undelete-subvol.c
+++ b/undelete-subvol.c
@@ -5,6 +5,8 @@
 
 #include "ctree.h"
 #include "disk-io.h"
+#include "transaction.h"
+#include "messages.h"
 
 /*
  * Determines whether the subvolume is intact, according to the drop_progress
@@ -28,3 +30,52 @@ static bool is_subvol_intact(struct btrfs_fs_info *fs_info, u64 subvol_id)
 	/* the subvolume is intact if the objectid of drop_progress == 0 */
 	return !btrfs_disk_key_objectid(&root->root_item.drop_progress);
 }
+
+/*
+ * Clear BTRFS_ROOT_SUBVOL_DEAD flag.
+ *
+ * @subvol_id	specify the root_item which will be modified.
+ *
+ * Return 0 if no error occurred.
+ */
+static int recover_dead_root(struct btrfs_trans_handle *trans, u64 subvol_id)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_key key;
+	struct btrfs_path path;
+	struct extent_buffer *leaf;
+	struct btrfs_root_item root_item;
+	u64 root_flags;
+	u64 offset;
+	int ret;
+
+	key.objectid = subvol_id;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = 0;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(trans, root, &key, &path, 0, 0);
+	if (ret) {
+		error("couldn't find ROOT_ITEM for %llu failed: %d",
+				subvol_id, ret);
+		goto out;
+	}
+
+	leaf = path.nodes[0];
+
+	offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
+	read_extent_buffer(leaf, &root_item, offset, sizeof(root_item));
+
+	/* Clear BTRFS_ROOT_SUBVOL_DEAD */
+	root_flags = btrfs_root_flags(&root_item);
+	btrfs_set_root_flags(&root_item,
+			     root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
+
+	write_extent_buffer(leaf, &root_item, offset, sizeof(root_item));
+	btrfs_mark_buffer_dirty(leaf);
+
+out:
+	btrfs_release_path(&path);
+	return ret;
+}
-- 
2.17.0

[PATCH v3 06/10] btrfs-progs: undelete-subvol: introduce link_subvol_to_lostfound

[Lu Fengqi]

The function will create lost+found directory, link the deleted
subvolume specified by the subvol_id to the directory, update the
information of root_item and cleanup the associated orphan item.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
---
V3:
pass btrfs_fs_info instead of btrfs_root;
add Reviewed-by from Qu Wenruo.

 undelete-subvol.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/undelete-subvol.c b/undelete-subvol.c
index 6d3ef19977d6..9851998ec3df 100644
--- a/undelete-subvol.c
+++ b/undelete-subvol.c
@@ -79,3 +79,79 @@ out:
 	btrfs_release_path(&path);
 	return ret;
 }
+
+/*
+ * Recover a subvolume specified by subvol_id, and link it to the lost+found
+ * directory.
+ *
+ * @subvol_id: specify the subvolume which will be linked, and also be the part
+ * of the subvolume name.
+ *
+ * Return 0 if no error occurred.
+ */
+static int link_subvol_to_lostfound(struct btrfs_fs_info *fs_info,
+				    u64 subvol_id)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_root *fs_root = fs_info->fs_root;
+	char buf[BTRFS_NAME_LEN + 1] = {0}; /* 1 for snprintf null */
+	char *dir_name = "lost+found";
+	u64 lost_found_ino = 0;
+	u32 mode = 0700;
+	int ret;
+
+	/*
+	 * For link subvolume to lost+found,
+	 * 2 for parent(256)'s dir_index and dir_item
+	 * 2 for lost+found dir's inode_item and inode_ref
+	 * 2 for lost+found dir's dir_index and dir_item for the subvolume
+	 * 2 for the subvolume's root_ref and root_backref
+	 */
+	trans = btrfs_start_transaction(fs_root, 8);
+	if (IS_ERR(trans)) {
+		error("unable to start transaction");
+		ret = PTR_ERR(trans);
+		goto out;
+	}
+
+	/* Create lost+found directory */
+	ret = btrfs_mkdir(trans, fs_root, dir_name, strlen(dir_name),
+			  BTRFS_FIRST_FREE_OBJECTID, &lost_found_ino,
+			  mode);
+	if (ret < 0) {
+		error("failed to create '%s' dir: %d", dir_name, ret);
+		goto out;
+	}
+
+	/* Link the subvolume to lost+found directory */
+	snprintf(buf, BTRFS_NAME_LEN + 1, "sub%llu", subvol_id);
+	ret = btrfs_link_subvol(trans, fs_root, buf, subvol_id, lost_found_ino,
+				false);
+	if (ret) {
+		error("failed to link the subvol %llu: %d", subvol_id, ret);
+		goto out;
+	}
+
+	/* Clear root flags BTRFS_ROOT_SUBVOL_DEAD */
+	ret = recover_dead_root(trans, subvol_id);
+	if (ret)
+		goto out;
+
+	/* Delete the orphan item after undeletion is completed. */
+	ret = btrfs_del_orphan_item(trans, root, subvol_id);
+	if (ret) {
+		error("failed to delete the orphan_item for %llu: %d",
+				subvol_id, ret);
+		goto out;
+	}
+
+	ret = btrfs_commit_transaction(trans, fs_root);
+	if (ret) {
+		error("transaction commit failed: %d", ret);
+		goto out;
+	}
+
+out:
+	return ret;
+}
-- 
2.17.0

[PATCH v3 07/10] btrfs-progs: undelete-subvol: introduce btrfs_undelete_subvols

[Lu Fengqi]

The function default will traverse the all orphan items on the tree root,
and recover the all intact subvolumes. If subvol_id is specified, then only
the corresponding subvolume will be recovered.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3:
pass btrfs_fs_info instead of btrfs_root;
rename btrfs_undelete_intact_subvols to btrfs_undelete_subvols;
use btrfs_previous_item to iterate.
V2: add subvol_id argument to specify subvol_id instead of recovering
all subvolumes.

 undelete-subvol.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++
 undelete-subvol.h | 11 ++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 undelete-subvol.h

diff --git a/undelete-subvol.c b/undelete-subvol.c
index 9851998ec3df..6b9803d4c590 100644
--- a/undelete-subvol.c
+++ b/undelete-subvol.c
@@ -7,6 +7,7 @@
 #include "disk-io.h"
 #include "transaction.h"
 #include "messages.h"
+#include "undelete-subvol.h"
 
 /*
  * Determines whether the subvolume is intact, according to the drop_progress
@@ -155,3 +156,72 @@ static int link_subvol_to_lostfound(struct btrfs_fs_info *fs_info,
 out:
 	return ret;
 }
+
+/*
+ * Traverse all orphan items on the root tree, restore them to the lost+found
+ * directory if the corresponding subvolumes are still intact left on the disk.
+ *
+ * @subvol_id	if not set to 0, skip other subvolumes and only recover the
+ *		subvolume specified by @subvol_id.
+ *
+ * Return 0 if no error occurred even if no subvolume was recovered.
+ */
+int btrfs_undelete_subvols(struct btrfs_fs_info *fs_info, u64 subvol_id)
+{
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_key key;
+	struct btrfs_path path;
+	u64 found_count = 0;
+	u64 recovered_count = 0;
+	int ret = 0;
+
+	key.objectid = BTRFS_ORPHAN_OBJECTID;
+	key.type = BTRFS_ORPHAN_ITEM_KEY;
+	key.offset = subvol_id ? subvol_id + 1 : (u64)-1;
+
+	btrfs_init_path(&path);
+	while (subvol_id != key.offset) {
+		ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+		if (ret < 0) {
+			error("search ORPHAN_ITEM for %llu failed.\n",
+			      key.offset);
+			btrfs_release_path(&path);
+			break;
+		}
+
+		ret = btrfs_previous_item(root, &path, BTRFS_ORPHAN_OBJECTID,
+					  BTRFS_ORPHAN_ITEM_KEY);
+		if (ret) {
+			btrfs_release_path(&path);
+			break;
+		}
+
+		btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+		btrfs_release_path(&path);
+
+		/* If subvol_id is non-zero, skip other deleted subvolume. */
+		if (subvol_id && subvol_id != key.offset) {
+			ret = -ENOENT;
+			break;
+		}
+
+		if (!is_subvol_intact(fs_info, key.offset))
+			continue;
+
+		/* Here we can confirm there is an intact subvolume. */
+		found_count++;
+		ret = link_subvol_to_lostfound(fs_info, key.offset);
+		if (ret == 0) {
+			recovered_count++;
+			printf(
+		"Recovered subvolume %llu to lost+found successfully.\n",
+				key.offset);
+		}
+
+	}
+
+	printf("Found %llu deleted subvols left intact\n", found_count);
+	printf("Recovered %llu deleted subvols\n", found_count);
+
+	return ret;
+}
diff --git a/undelete-subvol.h b/undelete-subvol.h
new file mode 100644
index 000000000000..a98d8ab90cea
--- /dev/null
+++ b/undelete-subvol.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018 Fujitsu.  All rights reserved.
+ */
+
+#ifndef __BTRFS_UNDELETE_SUBVOLUME_H__
+#define __BTRFS_UNDELETE_SUBVOLUME_H__
+
+int btrfs_undelete_subvols(struct btrfs_fs_info *fs_info, u64 subvol_id);
+
+#endif
-- 
2.17.0

[PATCH v3 08/10] btrfs-progs: undelete-subvol: add undelete-subvol subcommand

[Lu Fengqi]

Add the undelete-subvol subcommand for btrfs rescue. This subcommand is
used to recover deleted subvolume left intact on the device.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3: remove OPEN_CTREE_PARTIAL flag.
V2: add -s option to specify subvol_id.

 cmds-rescue.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/cmds-rescue.c b/cmds-rescue.c
index c40088ad374e..536d6b37ac50 100644
--- a/cmds-rescue.c
+++ b/cmds-rescue.c
@@ -25,6 +25,7 @@
 #include "disk-io.h"
 #include "commands.h"
 #include "utils.h"
+#include "undelete-subvol.h"
 #include "help.h"
 
 static const char * const rescue_cmd_group_usage[] = {
@@ -248,6 +249,72 @@ out:
 	return !!ret;
 }
 
+static const char * const cmd_rescue_undelete_subvol_usage[] = {
+	"btrfs rescue undelete-subvol [-s <subvolid>] <device>",
+	"Undelete deleted subvolume",
+	"All deleted subvolume that still left intact on the device will be",
+	"recovered. If -s <subvolid> option is given, then just recover the",
+	"subvolume which specified by <subvolid>.",
+	"",
+	"-s <subvolid>	specify the subvolume which will be recovered.",
+	NULL
+};
+
+static int cmd_rescue_undelete_subvol(int argc, char **argv)
+{
+	struct btrfs_fs_info *fs_info;
+	char *devname;
+	u64 subvol_id = 0;
+	int ret;
+
+	while (1) {
+		int c = getopt(argc, argv, "s:");
+
+		if (c < 0)
+			break;
+		switch (c) {
+		case 's':
+			subvol_id = arg_strtou64(optarg);
+			if (!is_fstree(subvol_id)) {
+				error("%llu is not a valid subvolume id",
+						subvol_id);
+				ret = -EINVAL;
+				goto out;
+			}
+			break;
+		default:
+			usage(cmd_rescue_undelete_subvol_usage);
+		}
+	}
+
+	if (check_argc_exact(argc - optind, 1))
+		usage(cmd_rescue_undelete_subvol_usage);
+
+	devname = argv[optind];
+	ret = check_mounted(devname);
+	if (ret < 0) {
+		error("could not check mount status: %s", strerror(-ret));
+		goto out;
+	} else if (ret) {
+		error("%s is currently mounted", devname);
+		ret = -EBUSY;
+		goto out;
+	}
+
+	fs_info = open_ctree_fs_info(devname, 0, 0, 0, OPEN_CTREE_WRITES);
+	if (!fs_info) {
+		error("could not open btrfs");
+		ret = -EIO;
+		goto out;
+	}
+
+	ret = btrfs_undelete_subvols(fs_info, subvol_id);
+
+	close_ctree(fs_info->tree_root);
+out:
+	return ret;
+}
+
 static const char rescue_cmd_group_info[] =
 "toolbox for specific rescue operations";
 
@@ -260,6 +327,8 @@ const struct cmd_group rescue_cmd_group = {
 		{ "zero-log", cmd_rescue_zero_log, cmd_rescue_zero_log_usage, NULL, 0},
 		{ "fix-device-size", cmd_rescue_fix_device_size,
 			cmd_rescue_fix_device_size_usage, NULL, 0},
+		{ "undelete-subvol", cmd_rescue_undelete_subvol,
+			cmd_rescue_undelete_subvol_usage, NULL, 0},
 		NULL_CMD_STRUCT
 	}
 };
-- 
2.17.0

[PATCH v3 09/10] btrfs-progs: tests: add testcase for undelete-subvol

[Lu Fengqi]

The testcase checks the functionality of "btrfs rescue undelete-subvol",
including recovering an intact subvolume, and handling correctly
incomplete subvolume.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3:
rename testcase to 031-undelete-subvol;
rename images and add image description to test.sh.
V2: add shell quoting to test script.

 .../031-undelete-subvol/intact_subvolume.img  | Bin 0 -> 4096 bytes
 .../subvolume_in_drop_progress.raw.xz         | Bin 0 -> 23452 bytes
 tests/misc-tests/031-undelete-subvol/test.sh  |  38 ++++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 tests/misc-tests/031-undelete-subvol/intact_subvolume.img
 create mode 100644 tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz
 create mode 100755 tests/misc-tests/031-undelete-subvol/test.sh

diff --git a/tests/misc-tests/031-undelete-subvol/intact_subvolume.img b/tests/misc-tests/031-undelete-subvol/intact_subvolume.img
new file mode 100644
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diff --git a/tests/misc-tests/031-undelete-subvol/test.sh b/tests/misc-tests/031-undelete-subvol/test.sh
new file mode 100755
index 000000000000..c84eb310baef
--- /dev/null
+++ b/tests/misc-tests/031-undelete-subvol/test.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+# Test undelete-subvol can recover the intact subvolume, and can skip the
+# incomplete subvolume.
+#
+# For intact_subvolume.img it has 1 orphan root and it can be recovered.
+# For subvolume_in_drop_progress.raw.xz it has 2 orphan roots while only
+# one can be recovered.
+
+source "$TOP/tests/common"
+
+check_prereq btrfs
+check_prereq btrfs-image
+
+setup_root_helper
+
+check_image()
+{
+	TEST_DEV="$1"
+
+	run_check_stdout "$TOP/btrfs" rescue undelete-subvol "$TEST_DEV" \
+		| grep -q "Recovered 1 deleted subvols" \
+		|| _fail "failed to undelete subvol $image" >&2
+
+	run_check "$TOP/btrfs" check "$TEST_DEV"
+
+	# check whether the recovered image can be mounted normally
+	run_check_mount_test_dev
+
+	run_check_stdout $SUDO_HELPER "$TOP/btrfs" subvolume list "$TEST_MNT" \
+		| grep -q "lost+found" \
+		|| _fail "failed to find the recovered subvol $image" >&2
+
+	run_check_umount_test_dev "$TEST_MNT"
+
+	rm "$TEST_DEV"
+}
+
+check_all_images
-- 
2.17.0

[PATCH v3.1 09/10] btrfs-progs: tests: add testcase for undelete-subvol

[Lu Fengqi]

The testcase checks the functionality of "btrfs rescue undelete-subvol",
including recovering an intact subvolume, and handling correctly
incomplete subvolume.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V3.1: remove unnecessary check_prereq btrfs-image
V3:
rename testcase to 031-undelete-subvol;
rename images and add image description to test.sh.
V2: add shell quoting to test script.

 .../031-undelete-subvol/intact_subvolume.img  | Bin 0 -> 4096 bytes
 .../subvolume_in_drop_progress.raw.xz         | Bin 0 -> 23452 bytes
 tests/misc-tests/031-undelete-subvol/test.sh  |  37 ++++++++++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 tests/misc-tests/031-undelete-subvol/intact_subvolume.img
 create mode 100644 tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz
 create mode 100755 tests/misc-tests/031-undelete-subvol/test.sh

diff --git a/tests/misc-tests/031-undelete-subvol/intact_subvolume.img b/tests/misc-tests/031-undelete-subvol/intact_subvolume.img
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diff --git a/tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz b/tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz
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diff --git a/tests/misc-tests/031-undelete-subvol/test.sh b/tests/misc-tests/031-undelete-subvol/test.sh
new file mode 100755
index 000000000000..f5eb0f46da7d
--- /dev/null
+++ b/tests/misc-tests/031-undelete-subvol/test.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+# Test undelete-subvol can recover the intact subvolume, and can skip the
+# incomplete subvolume.
+#
+# For intact_subvolume.img it has 1 orphan root and it can be recovered.
+# For subvolume_in_drop_progress.raw.xz it has 2 orphan roots while only
+# one can be recovered.
+
+source "$TOP/tests/common"
+
+check_prereq btrfs
+
+setup_root_helper
+
+check_image()
+{
+	TEST_DEV="$1"
+
+	run_check_stdout "$TOP/btrfs" rescue undelete-subvol "$TEST_DEV" \
+		| grep -q "Recovered 1 deleted subvols" \
+		|| _fail "failed to undelete subvol $image" >&2
+
+	run_check "$TOP/btrfs" check "$TEST_DEV"
+
+	# check whether the recovered image can be mounted normally
+	run_check_mount_test_dev
+
+	run_check_stdout $SUDO_HELPER "$TOP/btrfs" subvolume list "$TEST_MNT" \
+		| grep -q "lost+found" \
+		|| _fail "failed to find the recovered subvol $image" >&2
+
+	run_check_umount_test_dev "$TEST_MNT"
+
+	rm "$TEST_DEV"
+}
+
+check_all_images
-- 
2.17.0

[PATCH v3 10/10] btrfs-progs: undelete-subvol: update completion and documentation

[Lu Fengqi]

Add undelete-subvol to btrfs-completion, and update btrfs-rescue
documentation to introduce undelete-subvol.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
---
V2: just add -s option documentation.

 Documentation/btrfs-rescue.asciidoc | 12 ++++++++++++
 btrfs-completion                    |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/btrfs-rescue.asciidoc b/Documentation/btrfs-rescue.asciidoc
index f94a0ff2b45e..573a865b1158 100644
--- a/Documentation/btrfs-rescue.asciidoc
+++ b/Documentation/btrfs-rescue.asciidoc
@@ -60,6 +60,18 @@ assume an answer of 'yes' to all questions.
 -v::::
 verbose mode.
 
+*undelete-subvol* <device>::
+Undelete deleted subvolumes that still left intact on the device.
++
+This command will create the lost+found directory, and recover all the
+subvolumes to this directory with the name "sub<id>". If -s <subvolid> option
+is given, then just recover the subvolume which specified by <subvolid>.
++
+`Options`
++
+-s::::
+specify the subvolume which will be recovered.
+
 *zero-log* <device>::
 clear the filesystem log tree
 +
diff --git a/btrfs-completion b/btrfs-completion
index ae683f4ecf61..859595155a4b 100644
--- a/btrfs-completion
+++ b/btrfs-completion
@@ -35,7 +35,7 @@ _btrfs()
 	commands_balance='start pause cancel resume status'
 	commands_device='scan add delete remove ready stats usage'
 	commands_scrub='start cancel resume status'
-	commands_rescue='chunk-recover super-recover zero-log'
+	commands_rescue='chunk-recover super-recover undelete-subvol zero-log'
 	commands_inspect_internal='inode-resolve logical-resolve subvolid-resolve rootid min-dev-size dump-tree dump-super tree-stats'
 	commands_property='get set list'
 	commands_quota='enable disable rescan'
-- 
2.17.0

Re: [PATCH v3 00/10] undelete subvolume offline version

[Lu Fengqi]

On Mon, May 07, 2018 at 11:10:23AM +0800, Lu Fengqi wrote:
>This patchset will add undelete-subvol subcommand for btrfs rescue.
>

Hi David

Although there are some disagreements about undeleting subvolumes online
implementation, the offline version is considered more acceptable. Would
you like to spend some time talking about your opinions?

-- 
Thanks,
Lu

>Patchset can be fetched from github:
>https://github.com/littleroad/btrfs-progs.git undelete
>
>v2->v3: fixed some issues pointed out by Qu.
>v1->v2: add -s option to allow user specify the subvolume which will be
>recovered.
>
>The first patch are not modified.
>For the rest, please see the changelog in the patches.
>
>Lu Fengqi (10):
>  btrfs-progs: copy btrfs_del_orphan_item from kernel
>  btrfs-progs: extract btrfs_link_subvol from btrfs_mksubvol
>  btrfs-progs: use btrfs_find_free_dir_index to find free inode index
>  btrfs-progs: undelete-subvol: introduce is_subvol_intact
>  btrfs-progs: undelete-subvol: introduce recover_dead_root
>  btrfs-progs: undelete-subvol: introduce link_subvol_to_lostfound
>  btrfs-progs: undelete-subvol: introduce btrfs_undelete_subvols
>  btrfs-progs: undelete-subvol: add undelete-subvol subcommand
>  btrfs-progs: tests: add testcase for undelete-subvol
>  btrfs-progs: undelete-subvol: update completion and documentation
>
> Documentation/btrfs-rescue.asciidoc           |  12 +
> Makefile                                      |   3 +-
> btrfs-completion                              |   2 +-
> cmds-rescue.c                                 |  69 ++++++
> convert/main.c                                |  59 ++++-
> ctree.h                                       |   8 +-
> inode.c                                       | 119 +++++----
> .../031-undelete-subvol/intact_subvolume.img  | Bin 0 -> 4096 bytes
> .../subvolume_in_drop_progress.raw.xz         | Bin 0 -> 23452 bytes
> tests/misc-tests/031-undelete-subvol/test.sh  |  38 +++
> undelete-subvol.c                             | 227 ++++++++++++++++++
> undelete-subvol.h                             |  11 +
> 12 files changed, 501 insertions(+), 47 deletions(-)
> create mode 100644 tests/misc-tests/031-undelete-subvol/intact_subvolume.img
> create mode 100644 tests/misc-tests/031-undelete-subvol/subvolume_in_drop_progress.raw.xz
> create mode 100755 tests/misc-tests/031-undelete-subvol/test.sh
> create mode 100644 undelete-subvol.c
> create mode 100644 undelete-subvol.h
>
>-- 
>2.17.0
>
>
>
>--
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