[PATCH v3 6/7] btrfs-progs: lowmem: optimization and repair for check_inode_extref()

[Su Yue <suy.fnst@cn.fujitsu.com>]

inode_extref is much similar with inode_ref, most codes are reused in
check_inode_extref().
Exceptions:
There is no need to check root directory, so remove it.
Make check_inode_extref() verify hash value with key offset now.

And lowmem check can detect errors about inode_extref and try to
repair errors.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
---
 check/mode-lowmem.c | 125 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 99 insertions(+), 26 deletions(-)

diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index 612e5e28e45b..53e4fdccd740 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -1182,37 +1182,86 @@ out:
  *
  * Return 0 if no error occurred.
  */
-static int check_inode_extref(struct btrfs_root *root,
-			      struct btrfs_key *ref_key,
-			      struct extent_buffer *node, int slot, u64 *refs,
-			      int mode)
+static int check_inode_extref(struct btrfs_root *root, struct btrfs_key *ref_key,
+			      struct btrfs_path *path, char *name_ret,
+			      u32 *namelen_ret, u64 *refs_ret, int mode)
 {
 	struct btrfs_key key;
 	struct btrfs_key location;
 	struct btrfs_inode_extref *extref;
+	struct extent_buffer *node;
 	char namebuf[BTRFS_NAME_LEN] = {0};
 	u32 total;
-	u32 cur = 0;
+	u32 cur;
 	u32 len;
 	u32 name_len;
 	u64 index;
 	u64 parent;
+	int err;
+	int tmp_err;
 	int ret;
-	int err = 0;
+	int slot;
+	u64 refs;
+	bool search_again = false;
 
 	location.objectid = ref_key->objectid;
 	location.type = BTRFS_INODE_ITEM_KEY;
 	location.offset = 0;
+begin:
+	cur = 0;
+	err = 0;
+	refs = *refs_ret;
+	*namelen_ret = 0;
+
+	/* since after repair, path and the dir item may be changed */
+	if (search_again) {
+		search_again = false;
+		btrfs_release_path(path);
+		ret = btrfs_search_slot(NULL, root, ref_key, path, 0, 0);
+		/*
+		 * The item was deleted, let the path point to the last checked
+		 * item.
+		 */
+		if (ret > 0) {
+			if (path->slots[0] == 0) {
+				ret = btrfs_prev_leaf(root, path);
+				/*
+				 * we are checking the inode item, there must
+				 * be some items before, the case shall never
+				 * happen.
+				 */
+				if (ret > 0)
+					ret = -EIO;
+				if (ret)
+					error(
+		"failed to get item before INODE_REF[%llu, %llu] root %llu: %s",
+					      ref_key->objectid, ref_key->offset,
+					      root->objectid, strerror(-ret));
+			} else {
+				path->slots[0]--;
+				ret = 0;
+			}
+			goto out;
+		} else if (ret < 0) {
+			err |= FATAL_ERROR;
+			goto out;
+		}
+	}
+
+	node = path->nodes[0];
+	slot = path->slots[0];
 
 	extref = btrfs_item_ptr(node, slot, struct btrfs_inode_extref);
 	total = btrfs_item_size_nr(node, slot);
 
-next:
-	/* update inode ref count */
-	(*refs)++;
-	name_len = btrfs_inode_extref_name_len(node, extref);
-	index = btrfs_inode_extref_index(node, extref);
+loop:
+	/* Update inode ref count */
+	refs++;
+	tmp_err = 0;
 	parent = btrfs_inode_extref_parent(node, extref);
+	index = btrfs_inode_extref_index(node, extref);
+	name_len = btrfs_inode_extref_name_len(node, extref);
+
 	if (name_len <= BTRFS_NAME_LEN) {
 		len = name_len;
 	} else {
@@ -1220,37 +1269,61 @@ next:
 		warning("root %llu INODE_EXTREF[%llu %llu] name too long",
 			root->objectid, ref_key->objectid, ref_key->offset);
 	}
+
 	read_extent_buffer(node, namebuf, (unsigned long)(extref + 1), len);
 
-	/* Check root dir ref name */
-	if (index == 0 && strncmp(namebuf, "..", name_len)) {
-		error("root %llu INODE_EXTREF[%llu %llu] ROOT_DIR name shouldn't be %s",
+	/* verify hash value */
+	if (ref_key->offset != btrfs_extref_hash(parent, namebuf, len)) {
+		err |= FATAL_ERROR;
+		error("root %llu INODE_EXTREF[%llu %llu] name %s namelen %u mode %d mismatch with its hash, wanted %llu have %llu",
 		      root->objectid, ref_key->objectid, ref_key->offset,
-		      namebuf);
-		err |= ROOT_DIR_ERROR;
+		      namebuf, len, mode, ref_key->offset,
+		      btrfs_extref_hash(parent, namebuf, len));
+		goto out;
+	}
+
+	/* copy the first name found to name_ret */
+	if (refs == 1 && name_ret) {
+		memcpy(name_ret, namebuf, len);
+		*namelen_ret = len;
 	}
 
-	/* find related dir_index */
+	/* Find related DIR_INDEX */
 	key.objectid = parent;
 	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = index;
-	ret = find_dir_item(root, &key, &location, namebuf, len, mode);
-	err |= ret;
+	tmp_err |= find_dir_item(root, &key, &location, namebuf, len,
+			    imode_to_type(mode));
 
-	/* find related dir_item */
+	/* Find related dir_item */
 	key.objectid = parent;
 	key.type = BTRFS_DIR_ITEM_KEY;
 	key.offset = btrfs_name_hash(namebuf, len);
-	ret = find_dir_item(root, &key, &location, namebuf, len, mode);
-	err |= ret;
+	tmp_err |= find_dir_item(root, &key, &location, namebuf, len,
+			    imode_to_type(mode));
+
+	if (tmp_err && repair) {
+		ret = repair_ternary_lowmem(root, parent, ref_key->objectid,
+			    index, namebuf, name_len, imode_to_type(mode),
+			    tmp_err);
+		if (!ret) {
+			search_again = true;
+			goto begin;
+		}
+	}
 
+	print_inode_ref_err(root, ref_key, index, namebuf, name_len,
+			    imode_to_type(mode), tmp_err);
+
+	err |= tmp_err;
 	len = sizeof(*extref) + name_len;
 	extref = (struct btrfs_inode_extref *)((char *)extref + len);
 	cur += len;
 
 	if (cur < total)
-		goto next;
-
+		goto loop;
+out:
+	*refs_ret = refs;
 	return err;
 }
 
@@ -2426,8 +2499,8 @@ static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path)
 				warning("root %llu EXTREF[%llu %llu] isn't supported",
 					root->objectid, key.objectid,
 					key.offset);
-			ret = check_inode_extref(root, &key, node, slot, &refs,
-						 mode);
+			ret = check_inode_extref(root, &key, path, namebuf,
+						 &name_len, &refs, mode);
 			err |= ret;
 			break;
 		}
-- 
2.17.1