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

[Nikolay Borisov <nborisov@suse.com>]

On 17.09.2018 10:28, Su Yue wrote:
> 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:

Please don't implement loops with labels, instead use the appropriate
loop construct. Otherwise just factor out the repetitive code in a
function and call that in a loop. Labels should ideally be used only for
error cases to terminate the current function.

> +	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;
>  		}
>