linux/fs/bcachefs/str_hash.c

// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "btree_cache.h"
#include "btree_update.h"
#include "dirent.h"
#include "fsck.h"
#include "str_hash.h"
#include "subvolume.h"

static int bch2_dirent_has_target(struct btree_trans *trans, struct bkey_s_c_dirent d)
{
	if (d.v->d_type == DT_SUBVOL) {
		struct bch_subvolume subvol;
		int ret = bch2_subvolume_get(trans, le32_to_cpu(d.v->d_child_subvol),
					     false, &subvol);
		if (ret && !bch2_err_matches(ret, ENOENT))
			return ret;
		return !ret;
	} else {
		struct btree_iter iter;
		struct bkey_s_c k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
				SPOS(0, le64_to_cpu(d.v->d_inum), d.k->p.snapshot), 0);
		int ret = bkey_err(k);
		if (ret)
			return ret;

		ret = bkey_is_inode(k.k);
		bch2_trans_iter_exit(trans, &iter);
		return ret;
	}
}

static int bch2_fsck_rename_dirent(struct btree_trans *trans,
				   struct snapshots_seen *s,
				   const struct bch_hash_desc desc,
				   struct bch_hash_info *hash_info,
				   struct bkey_s_c_dirent old,
				   bool *updated_before_k_pos)
{
	struct bch_fs *c = trans->c;
	struct qstr old_name = bch2_dirent_get_name(old);
	struct bkey_i_dirent *new = bch2_trans_kmalloc(trans, BKEY_U64s_MAX * sizeof(u64));
	int ret = PTR_ERR_OR_ZERO(new);
	if (ret)
		return ret;

	bkey_dirent_init(&new->k_i);
	dirent_copy_target(new, old);
	new->k.p = old.k->p;

	char *renamed_buf = bch2_trans_kmalloc(trans, old_name.len + 20);
	ret = PTR_ERR_OR_ZERO(renamed_buf);
	if (ret)
		return ret;

	for (unsigned i = 0; i < 1000; i++) {
		new->k.u64s = BKEY_U64s_MAX;

		struct qstr renamed_name = (struct qstr) QSTR_INIT(renamed_buf,
					sprintf(renamed_buf, "%.*s.fsck_renamed-%u",
						old_name.len, old_name.name, i));

		ret = bch2_dirent_init_name(c, new, hash_info, &renamed_name, NULL);
		if (ret)
			return ret;

		ret = bch2_hash_set_in_snapshot(trans, bch2_dirent_hash_desc, hash_info,
						(subvol_inum) { 0, old.k->p.inode },
						old.k->p.snapshot, &new->k_i,
						BTREE_UPDATE_internal_snapshot_node|
						STR_HASH_must_create);
		if (ret && !bch2_err_matches(ret, EEXIST))
			break;
		if (!ret) {
			if (bpos_lt(new->k.p, old.k->p))
				*updated_before_k_pos = true;
			break;
		}
	}

	ret = ret ?: bch2_fsck_update_backpointers(trans, s, desc, hash_info, &new->k_i);
	bch_err_fn(c, ret);
	return ret;
}

static noinline int hash_pick_winner(struct btree_trans *trans,
				     const struct bch_hash_desc desc,
				     struct bch_hash_info *hash_info,
				     struct bkey_s_c k1,
				     struct bkey_s_c k2)
{
	if (bkey_val_bytes(k1.k) == bkey_val_bytes(k2.k) &&
	    !memcmp(k1.v, k2.v, bkey_val_bytes(k1.k)))
		return 0;

	switch (desc.btree_id) {
	case BTREE_ID_dirents: {
		int ret = bch2_dirent_has_target(trans, bkey_s_c_to_dirent(k1));
		if (ret < 0)
			return ret;
		if (!ret)
			return 0;

		ret = bch2_dirent_has_target(trans, bkey_s_c_to_dirent(k2));
		if (ret < 0)
			return ret;
		if (!ret)
			return 1;
		return 2;
	}
	default:
		return 0;
	}
}

/*
 * str_hash lookups across snapshots break in wild ways if hash_info in
 * different snapshot versions doesn't match - so if we find one mismatch, check
 * them all
 */
int bch2_repair_inode_hash_info(struct btree_trans *trans,
				struct bch_inode_unpacked *snapshot_root)
{
	struct bch_fs *c = trans->c;
	struct btree_iter iter;
	struct bkey_s_c k;
	struct printbuf buf = PRINTBUF;
	bool need_commit = false;
	int ret = 0;

	for_each_btree_key_norestart(trans, iter, BTREE_ID_inodes,
				     POS(0, snapshot_root->bi_inum),
				     BTREE_ITER_all_snapshots, k, ret) {
		if (bpos_ge(k.k->p, SPOS(0, snapshot_root->bi_inum, snapshot_root->bi_snapshot)))
			break;
		if (!bkey_is_inode(k.k))
			continue;

		struct bch_inode_unpacked inode;
		ret = bch2_inode_unpack(k, &inode);
		if (ret)
			break;

		if (inode.bi_hash_seed		== snapshot_root->bi_hash_seed &&
		    INODE_STR_HASH(&inode)	== INODE_STR_HASH(snapshot_root)) {
#ifdef CONFIG_BCACHEFS_DEBUG
			struct bch_hash_info hash1 = bch2_hash_info_init(c, snapshot_root);
			struct bch_hash_info hash2 = bch2_hash_info_init(c, &inode);

			BUG_ON(hash1.type != hash2.type ||
			       memcmp(&hash1.siphash_key,
				      &hash2.siphash_key,
				      sizeof(hash1.siphash_key)));
#endif
			continue;
		}

		printbuf_reset(&buf);
		prt_printf(&buf, "inode %llu hash info in snapshots %u %u don't match\n",
			   snapshot_root->bi_inum,
			   inode.bi_snapshot,
			   snapshot_root->bi_snapshot);

		bch2_prt_str_hash_type(&buf, INODE_STR_HASH(&inode));
		prt_printf(&buf, " %llx\n", inode.bi_hash_seed);

		bch2_prt_str_hash_type(&buf, INODE_STR_HASH(snapshot_root));
		prt_printf(&buf, " %llx", snapshot_root->bi_hash_seed);

		if (fsck_err(trans, inode_snapshot_mismatch, "%s", buf.buf)) {
			inode.bi_hash_seed = snapshot_root->bi_hash_seed;
			SET_INODE_STR_HASH(&inode, INODE_STR_HASH(snapshot_root));

			ret = __bch2_fsck_write_inode(trans, &inode);
			if (ret)
				break;
			need_commit = true;
		}
	}

	if (ret)
		goto err;

	if (!need_commit) {
		struct printbuf buf = PRINTBUF;
		bch2_log_msg_start(c, &buf);

		prt_printf(&buf, "inode %llu hash info mismatch with root, but mismatch not found\n",
			   snapshot_root->bi_inum);

		prt_printf(&buf, "root snapshot %u ", snapshot_root->bi_snapshot);
		bch2_prt_str_hash_type(&buf, INODE_STR_HASH(snapshot_root));
		prt_printf(&buf, " %llx\n", snapshot_root->bi_hash_seed);
#if 0
		prt_printf(&buf, "vs   snapshot %u ", hash_info->inum_snapshot);
		bch2_prt_str_hash_type(&buf, hash_info->type);
		prt_printf(&buf, " %llx %llx", hash_info->siphash_key.k0, hash_info->siphash_key.k1);
#endif
		bch2_print_str(c, KERN_ERR, buf.buf);
		printbuf_exit(&buf);
		ret = bch_err_throw(c, fsck_repair_unimplemented);
		goto err;
	}

	ret = bch2_trans_commit(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc) ?:
		-BCH_ERR_transaction_restart_nested;
err:
fsck_err:
	printbuf_exit(&buf);
	bch2_trans_iter_exit(trans, &iter);
	return ret;
}

/*
 * All versions of the same inode in different snapshots must have the same hash
 * seed/type: verify that the hash info we're using matches the root
 */
static noinline int check_inode_hash_info_matches_root(struct btree_trans *trans, u64 inum,
						       struct bch_hash_info *hash_info)
{
	struct bch_inode_unpacked snapshot_root;
	int ret = bch2_inode_find_snapshot_root(trans, inum, &snapshot_root);
	if (ret)
		return ret;

	struct bch_hash_info hash_root = bch2_hash_info_init(trans->c, &snapshot_root);
	if (hash_info->type != hash_root.type ||
	    memcmp(&hash_info->siphash_key,
		   &hash_root.siphash_key,
		   sizeof(hash_root.siphash_key)))
		ret = bch2_repair_inode_hash_info(trans, &snapshot_root);

	return ret;
}

/* Put a str_hash key in its proper location, checking for duplicates */
int bch2_str_hash_repair_key(struct btree_trans *trans,
			     struct snapshots_seen *s,
			     const struct bch_hash_desc *desc,
			     struct bch_hash_info *hash_info,
			     struct btree_iter *k_iter, struct bkey_s_c k,
			     struct btree_iter *dup_iter, struct bkey_s_c dup_k,
			     bool *updated_before_k_pos)
{
	struct bch_fs *c = trans->c;
	struct printbuf buf = PRINTBUF;
	bool free_snapshots_seen = false;
	int ret = 0;

	if (!s) {
		s = bch2_trans_kmalloc(trans, sizeof(*s));
		ret = PTR_ERR_OR_ZERO(s);
		if (ret)
			goto out;

		s->pos = k_iter->pos;
		darray_init(&s->ids);

		ret = bch2_get_snapshot_overwrites(trans, desc->btree_id, k_iter->pos, &s->ids);
		if (ret)
			goto out;

		free_snapshots_seen = true;
	}

	if (!dup_k.k) {
		struct bkey_i *new = bch2_bkey_make_mut_noupdate(trans, k);
		ret = PTR_ERR_OR_ZERO(new);
		if (ret)
			goto out;

		dup_k = bch2_hash_set_or_get_in_snapshot(trans, dup_iter, *desc, hash_info,
				       (subvol_inum) { 0, new->k.p.inode },
				       new->k.p.snapshot, new,
				       STR_HASH_must_create|
				       BTREE_ITER_with_updates|
				       BTREE_UPDATE_internal_snapshot_node);
		ret = bkey_err(dup_k);
		if (ret)
			goto out;
		if (dup_k.k)
			goto duplicate_entries;

		if (bpos_lt(new->k.p, k.k->p))
			*updated_before_k_pos = true;

		ret =   bch2_insert_snapshot_whiteouts(trans, desc->btree_id,
						       k_iter->pos, new->k.p) ?:
			bch2_hash_delete_at(trans, *desc, hash_info, k_iter,
					    BTREE_ITER_with_updates|
					    BTREE_UPDATE_internal_snapshot_node) ?:
			bch2_fsck_update_backpointers(trans, s, *desc, hash_info, new) ?:
			bch2_trans_commit(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc) ?:
			-BCH_ERR_transaction_restart_commit;
	} else {
duplicate_entries:
		ret = hash_pick_winner(trans, *desc, hash_info, k, dup_k);
		if (ret < 0)
			goto out;

		if (!fsck_err(trans, hash_table_key_duplicate,
			      "duplicate hash table keys%s:\n%s",
			      ret != 2 ? "" : ", both point to valid inodes",
			      (printbuf_reset(&buf),
			       bch2_bkey_val_to_text(&buf, c, k),
			       prt_newline(&buf),
			       bch2_bkey_val_to_text(&buf, c, dup_k),
			       buf.buf)))
			goto out;

		switch (ret) {
		case 0:
			ret = bch2_hash_delete_at(trans, *desc, hash_info, k_iter, 0);
			break;
		case 1:
			ret = bch2_hash_delete_at(trans, *desc, hash_info, dup_iter, 0);
			break;
		case 2:
			ret = bch2_fsck_rename_dirent(trans, s, *desc, hash_info,
						      bkey_s_c_to_dirent(k),
						      updated_before_k_pos) ?:
				bch2_hash_delete_at(trans, *desc, hash_info, k_iter,
						    BTREE_ITER_with_updates);
			goto out;
		}

		ret = bch2_trans_commit(trans, NULL, NULL, 0) ?:
			-BCH_ERR_transaction_restart_commit;
	}
out:
fsck_err:
	bch2_trans_iter_exit(trans, dup_iter);
	printbuf_exit(&buf);
	if (free_snapshots_seen)
		darray_exit(&s->ids);
	return ret;
}

int __bch2_str_hash_check_key(struct btree_trans *trans,
			      struct snapshots_seen *s,
			      const struct bch_hash_desc *desc,
			      struct bch_hash_info *hash_info,
			      struct btree_iter *k_iter, struct bkey_s_c hash_k,
			      bool *updated_before_k_pos)
{
	struct bch_fs *c = trans->c;
	struct btree_iter iter = {};
	struct printbuf buf = PRINTBUF;
	struct bkey_s_c k;
	int ret = 0;

	u64 hash = desc->hash_bkey(hash_info, hash_k);
	if (hash_k.k->p.offset < hash)
		goto bad_hash;

	for_each_btree_key_norestart(trans, iter, desc->btree_id,
				     SPOS(hash_k.k->p.inode, hash, hash_k.k->p.snapshot),
				     BTREE_ITER_slots|
				     BTREE_ITER_with_updates, k, ret) {
		if (bkey_eq(k.k->p, hash_k.k->p))
			break;

		if (k.k->type == desc->key_type &&
		    !desc->cmp_bkey(k, hash_k)) {
			ret =	check_inode_hash_info_matches_root(trans, hash_k.k->p.inode,
								   hash_info) ?:
				bch2_str_hash_repair_key(trans, s, desc, hash_info,
							 k_iter, hash_k,
							 &iter, k, updated_before_k_pos);
			break;
		}

		if (bkey_deleted(k.k))
			goto bad_hash;
	}
	bch2_trans_iter_exit(trans, &iter);
out:
fsck_err:
	printbuf_exit(&buf);
	return ret;
bad_hash:
	bch2_trans_iter_exit(trans, &iter);
	/*
	 * Before doing any repair, check hash_info itself:
	 */
	ret = check_inode_hash_info_matches_root(trans, hash_k.k->p.inode, hash_info);
	if (ret)
		goto out;

	if (fsck_err(trans, hash_table_key_wrong_offset,
		     "hash table key at wrong offset: should be at %llu\n%s",
		     hash,
		     (bch2_bkey_val_to_text(&buf, c, hash_k), buf.buf)))
		ret = bch2_str_hash_repair_key(trans, s, desc, hash_info,
					       k_iter, hash_k,
					       &iter, bkey_s_c_null,
					       updated_before_k_pos);
	goto out;
}