Commit 69bca40d authored by Alexander Block's avatar Alexander Block Committed by Chris Mason
Browse files

Btrfs: don't assume to be on the correct extent in add_all_parents 



add_all_parents did assume that path is already at a correct extent data
item, which may not be true in case of data extents that were partly
rewritten and splitted.

We need to check if we're on a matching extent for every item and only
for the ones after the first. The loop is changed to do this now.

This patch also fixes a bug introduced with commit 3b127fd8 "Btrfs:
remove obsolete btrfs_next_leaf call from __resolve_indirect_ref".
The removal of next_leaf did sometimes result in slot==nritems when
the above described case happens, and thus resulting in invalid values
(e.g. wanted_obejctid) in add_all_parents (leading to missed backrefs
or even crashes).

Signed-off-by: default avatarAlexander Block <ablock84@googlemail.com>
Signed-off-by: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 1c8f52a5

fs/btrfs/backref.c

+52 −42
Original line number Diff line number Diff line
@@ -179,61 +179,74 @@ static int __add_prelim_ref(struct list_head *head, u64 root_id, 


static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,

				struct ulist *parents, int level,

				struct btrfs_key *key, u64 time_seq,

				struct btrfs_key *key_for_search, u64 time_seq,

				u64 wanted_disk_byte,

				const u64 *extent_item_pos)

{

	int ret;

	int slot = path->slots[level];

	struct extent_buffer *eb = path->nodes[level];

	int ret = 0;

	int slot;

	struct extent_buffer *eb;

	struct btrfs_key key;

	struct btrfs_file_extent_item *fi;

	struct extent_inode_elem *eie = NULL;

	u64 disk_byte;

	u64 wanted_objectid = key->objectid;



add_parent:

	if (level == 0 && extent_item_pos) {

		fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);

		ret = check_extent_in_eb(key, eb, fi, *extent_item_pos, &eie);

		if (ret < 0)

			return ret;

	}

	ret = ulist_add(parents, eb->start, (unsigned long)eie, GFP_NOFS);

	if (level != 0) {

		eb = path->nodes[level];

		ret = ulist_add(parents, eb->start, 0, GFP_NOFS);

		if (ret < 0)

			return ret;



	if (level != 0)

		return 0;

	}



	/*

	 * if the current leaf is full with EXTENT_DATA items, we must

	 * check the next one if that holds a reference as well.

	 * ref->count cannot be used to skip this check.

	 * repeat this until we don't find any additional EXTENT_DATA items.

	 * We normally enter this function with the path already pointing to

	 * the first item to check. But sometimes, we may enter it with

	 * slot==nritems. In that case, go to the next leaf before we continue.

	 */

	while (1) {

		eie = NULL;

	if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))

		ret = btrfs_next_old_leaf(root, path, time_seq);

		if (ret < 0)

			return ret;

		if (ret)

			return 0;



	while (!ret) {

		eb = path->nodes[0];

		for (slot = 0; slot < btrfs_header_nritems(eb); ++slot) {

			btrfs_item_key_to_cpu(eb, key, slot);

			if (key->objectid != wanted_objectid ||

			    key->type != BTRFS_EXTENT_DATA_KEY)

				return 0;

			fi = btrfs_item_ptr(eb, slot,

						struct btrfs_file_extent_item);

		slot = path->slots[0];



		btrfs_item_key_to_cpu(eb, &key, slot);



		if (key.objectid != key_for_search->objectid ||

		    key.type != BTRFS_EXTENT_DATA_KEY)

			break;



		fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);

		disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);

			if (disk_byte == wanted_disk_byte)

				goto add_parent;



		if (disk_byte == wanted_disk_byte) {

			eie = NULL;

			if (extent_item_pos) {

				ret = check_extent_in_eb(&key, eb, fi,

						*extent_item_pos,

						&eie);

				if (ret < 0)

					break;

			}

			if (!ret) {

				ret = ulist_add(parents, eb->start,

						(unsigned long)eie, GFP_NOFS);

				if (ret < 0)

					break;

				if (!extent_item_pos) {

					ret = btrfs_next_old_leaf(root, path,

							time_seq);

					continue;

				}

			}

		}

		ret = btrfs_next_old_item(root, path, time_seq);

	}



	return 0;

	if (ret > 0)

		ret = 0;

	return ret;

}



/*
@@ -250,7 +263,6 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info, 
	struct btrfs_path *path;

	struct btrfs_root *root;

	struct btrfs_key root_key;

	struct btrfs_key key = {0};

	struct extent_buffer *eb;

	int ret = 0;

	int root_level;
@@ -295,11 +307,9 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info, 
		goto out;

	}



	if (level == 0)

		btrfs_item_key_to_cpu(eb, &key, path->slots[0]);



	ret = add_all_parents(root, path, parents, level, &key, time_seq,

				ref->wanted_disk_byte, extent_item_pos);

	ret = add_all_parents(root, path, parents, level, &ref->key_for_search,

				time_seq, ref->wanted_disk_byte,

				extent_item_pos);

out:

	btrfs_free_path(path);

	return ret;

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