X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fntdb%2Fcheck.c;fp=ccan%2Fntdb%2Fcheck.c;h=5b6e90558255c11e78bad08b67288e78d9606abb;hp=0000000000000000000000000000000000000000;hb=d69ef83fcc2434ddaced1831184fb761ae6f09d3;hpb=ed95d8600afe1564ffd1783ae9ea0ef6324904dc

diff --git a/ccan/ntdb/check.c b/ccan/ntdb/check.c
new file mode 100644
index 00000000..5b6e9055
--- /dev/null
+++ b/ccan/ntdb/check.c
@@ -0,0 +1,726 @@
+ /*
+   Trivial Database 2: free list/block handling
+   Copyright (C) Rusty Russell 2010
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "private.h"
+#include <ccan/likely/likely.h>
+#include <ccan/asearch/asearch.h>
+
+/* We keep an ordered array of offsets. */
+static bool append(struct ntdb_context *ntdb,
+		   ntdb_off_t **arr, size_t *num, ntdb_off_t off)
+{
+	ntdb_off_t *new;
+
+	if (*num == 0) {
+		new = ntdb->alloc_fn(ntdb, sizeof(ntdb_off_t), ntdb->alloc_data);
+	} else {
+		new = ntdb->expand_fn(*arr, (*num + 1) * sizeof(ntdb_off_t),
+				  ntdb->alloc_data);
+	}
+	if (!new)
+		return false;
+	new[(*num)++] = off;
+	*arr = new;
+	return true;
+}
+
+static enum NTDB_ERROR check_header(struct ntdb_context *ntdb,
+				    ntdb_off_t *recovery,
+				    uint64_t *features,
+				    size_t *num_capabilities)
+{
+	uint64_t hash_test;
+	struct ntdb_header hdr;
+	enum NTDB_ERROR ecode;
+	ntdb_off_t off, next;
+
+	ecode = ntdb_read_convert(ntdb, 0, &hdr, sizeof(hdr));
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+	/* magic food should not be converted, so convert back. */
+	ntdb_convert(ntdb, hdr.magic_food, sizeof(hdr.magic_food));
+
+	hash_test = NTDB_HASH_MAGIC;
+	hash_test = ntdb_hash(ntdb, &hash_test, sizeof(hash_test));
+	if (hdr.hash_test != hash_test) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "check: hash test %llu should be %llu",
+				  (long long)hdr.hash_test,
+				  (long long)hash_test);
+	}
+
+	if (strcmp(hdr.magic_food, NTDB_MAGIC_FOOD) != 0) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "check: bad magic '%.*s'",
+				  (unsigned)sizeof(hdr.magic_food),
+				  hdr.magic_food);
+	}
+
+	/* Features which are used must be a subset of features offered. */
+	if (hdr.features_used & ~hdr.features_offered) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "check: features used (0x%llx) which"
+				  " are not offered (0x%llx)",
+				  (long long)hdr.features_used,
+				  (long long)hdr.features_offered);
+	}
+
+	*features = hdr.features_offered;
+	*recovery = hdr.recovery;
+	if (*recovery) {
+		if (*recovery < sizeof(hdr)
+		    || *recovery > ntdb->file->map_size) {
+			return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+					  "ntdb_check:"
+					  " invalid recovery offset %zu",
+					  (size_t)*recovery);
+		}
+	}
+
+	for (off = hdr.capabilities; off && ecode == NTDB_SUCCESS; off = next) {
+		const struct ntdb_capability *cap;
+		enum NTDB_ERROR e;
+
+		cap = ntdb_access_read(ntdb, off, sizeof(*cap), true);
+		if (NTDB_PTR_IS_ERR(cap)) {
+			return NTDB_PTR_ERR(cap);
+		}
+
+		/* All capabilities are unknown. */
+		e = unknown_capability(ntdb, "ntdb_check", cap->type);
+		next = cap->next;
+		ntdb_access_release(ntdb, cap);
+		if (e)
+			return e;
+		(*num_capabilities)++;
+	}
+
+	/* Don't check reserved: they *can* be used later. */
+	return NTDB_SUCCESS;
+}
+
+static int off_cmp(const ntdb_off_t *a, const ntdb_off_t *b)
+{
+	/* Can overflow an int. */
+	return *a > *b ? 1
+		: *a < *b ? -1
+		: 0;
+}
+
+static enum NTDB_ERROR check_entry(struct ntdb_context *ntdb,
+				   ntdb_off_t off_and_hash,
+				   ntdb_len_t bucket,
+				   ntdb_off_t used[],
+				   size_t num_used,
+				   size_t *num_found,
+				   enum NTDB_ERROR (*check)(NTDB_DATA,
+							    NTDB_DATA,
+							    void *),
+				   void *data)
+{
+	enum NTDB_ERROR ecode;
+	const struct ntdb_used_record *r;
+	const unsigned char *kptr;
+	ntdb_len_t klen, dlen;
+	uint32_t hash;
+	ntdb_off_t off = off_and_hash & NTDB_OFF_MASK;
+	ntdb_off_t *p;
+
+	/* Empty bucket is fine. */
+	if (!off_and_hash) {
+		return NTDB_SUCCESS;
+	}
+
+	/* This can't point to a chain, we handled those at toplevel. */
+	if (off_and_hash & (1ULL << NTDB_OFF_CHAIN_BIT)) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				   "ntdb_check: Invalid chain bit in offset "
+				   " %llu", (long long)off_and_hash);
+	}
+
+	p = asearch(&off, used, num_used, off_cmp);
+	if (!p) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				   "ntdb_check: Invalid offset"
+				   " %llu in hash", (long long)off);
+	}
+	/* Mark it invalid. */
+	*p ^= 1;
+	(*num_found)++;
+
+	r = ntdb_access_read(ntdb, off, sizeof(*r), true);
+	if (NTDB_PTR_IS_ERR(r)) {
+		return NTDB_PTR_ERR(r);
+	}
+	klen = rec_key_length(r);
+	dlen = rec_data_length(r);
+	ntdb_access_release(ntdb, r);
+
+	kptr = ntdb_access_read(ntdb, off + sizeof(*r), klen + dlen, false);
+	if (NTDB_PTR_IS_ERR(kptr)) {
+		return NTDB_PTR_ERR(kptr);
+	}
+
+	hash = ntdb_hash(ntdb, kptr, klen);
+
+	/* Are we in the right chain? */
+	if (bits_from(hash, 0, ntdb->hash_bits) != bucket) {
+		ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+				    NTDB_LOG_ERROR,
+				    "ntdb_check: Bad bucket %u vs %llu",
+				    bits_from(hash, 0, ntdb->hash_bits),
+				    (long long)bucket);
+	/* Next 8 bits should be the same as top bits of bucket. */
+	} else if (bits_from(hash, ntdb->hash_bits, NTDB_OFF_UPPER_STEAL)
+		   != bits_from(off_and_hash, 64-NTDB_OFF_UPPER_STEAL,
+				NTDB_OFF_UPPER_STEAL)) {
+		ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+				    NTDB_LOG_ERROR,
+				    "ntdb_check: Bad hash bits %llu vs %llu",
+				    (long long)off_and_hash,
+				    (long long)hash);
+	} else if (check) {
+		NTDB_DATA k, d;
+
+		k = ntdb_mkdata(kptr, klen);
+		d = ntdb_mkdata(kptr + klen, dlen);
+		ecode = check(k, d, data);
+	} else {
+		ecode = NTDB_SUCCESS;
+	}
+	ntdb_access_release(ntdb, kptr);
+
+	return ecode;
+}
+
+static enum NTDB_ERROR check_hash_chain(struct ntdb_context *ntdb,
+					ntdb_off_t off,
+					ntdb_len_t bucket,
+					ntdb_off_t used[],
+					size_t num_used,
+					size_t *num_found,
+					enum NTDB_ERROR (*check)(NTDB_DATA,
+								 NTDB_DATA,
+								 void *),
+					void *data)
+{
+	struct ntdb_used_record rec;
+	enum NTDB_ERROR ecode;
+	const ntdb_off_t *entries;
+	ntdb_len_t i, num;
+
+	/* This is a used entry. */
+	(*num_found)++;
+
+	ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec));
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+
+	if (rec_magic(&rec) != NTDB_CHAIN_MAGIC) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash chain magic %llu",
+				  (long long)rec_magic(&rec));
+	}
+
+	if (rec_data_length(&rec) % sizeof(ntdb_off_t)) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash chain data length %llu",
+				  (long long)rec_data_length(&rec));
+	}
+
+	if (rec_key_length(&rec) != 0) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash chain key length %llu",
+				  (long long)rec_key_length(&rec));
+	}
+
+	off += sizeof(rec);
+	num = rec_data_length(&rec) / sizeof(ntdb_off_t);
+	entries = ntdb_access_read(ntdb, off, rec_data_length(&rec), true);
+	if (NTDB_PTR_IS_ERR(entries)) {
+		return NTDB_PTR_ERR(entries);
+	}
+
+	/* Check each non-deleted entry in chain. */
+	for (i = 0; i < num; i++) {
+		ecode = check_entry(ntdb, entries[i], bucket,
+				    used, num_used, num_found, check, data);
+		if (ecode) {
+			break;
+		}
+	}
+
+	ntdb_access_release(ntdb, entries);
+	return ecode;
+}
+
+static enum NTDB_ERROR check_hash(struct ntdb_context *ntdb,
+				  ntdb_off_t used[],
+				  size_t num_used,
+				  size_t num_other_used,
+				  enum NTDB_ERROR (*check)(NTDB_DATA,
+							   NTDB_DATA,
+							   void *),
+				  void *data)
+{
+	enum NTDB_ERROR ecode;
+	struct ntdb_used_record rec;
+	const ntdb_off_t *entries;
+	ntdb_len_t i;
+	/* Free tables and capabilities also show up as used, as do we. */
+	size_t num_found = num_other_used + 1;
+
+	ecode = ntdb_read_convert(ntdb, NTDB_HASH_OFFSET, &rec, sizeof(rec));
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+
+	if (rec_magic(&rec) != NTDB_HTABLE_MAGIC) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash table magic %llu",
+				  (long long)rec_magic(&rec));
+	}
+
+	if (rec_data_length(&rec) != (sizeof(ntdb_off_t) << ntdb->hash_bits)) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash table data length %llu",
+				  (long long)rec_data_length(&rec));
+	}
+
+	if (rec_key_length(&rec) != 0) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Bad hash table key length %llu",
+				  (long long)rec_key_length(&rec));
+	}
+
+	entries = ntdb_access_read(ntdb, NTDB_HASH_OFFSET + sizeof(rec),
+				   rec_data_length(&rec), true);
+	if (NTDB_PTR_IS_ERR(entries)) {
+		return NTDB_PTR_ERR(entries);
+	}
+
+	for (i = 0; i < (1 << ntdb->hash_bits); i++) {
+		ntdb_off_t off = entries[i] & NTDB_OFF_MASK;
+		if (entries[i] & (1ULL << NTDB_OFF_CHAIN_BIT)) {
+			ecode = check_hash_chain(ntdb, off, i,
+						 used, num_used, &num_found,
+						 check, data);
+		} else {
+			ecode = check_entry(ntdb, entries[i], i,
+					    used, num_used, &num_found,
+					    check, data);
+		}
+		if (ecode) {
+			break;
+		}
+	}
+	ntdb_access_release(ntdb, entries);
+
+	if (ecode == NTDB_SUCCESS && num_found != num_used) {
+		ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				    "ntdb_check: Not all entries are in hash");
+	}
+	return ecode;
+}
+
+static enum NTDB_ERROR check_free(struct ntdb_context *ntdb,
+				 ntdb_off_t off,
+				 const struct ntdb_free_record *frec,
+				 ntdb_off_t prev, unsigned int ftable,
+				 unsigned int bucket)
+{
+	enum NTDB_ERROR ecode;
+
+	if (frec_magic(frec) != NTDB_FREE_MAGIC) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: offset %llu bad magic 0x%llx",
+				  (long long)off,
+				  (long long)frec->magic_and_prev);
+	}
+	if (frec_ftable(frec) != ftable) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: offset %llu bad freetable %u",
+				  (long long)off, frec_ftable(frec));
+
+	}
+
+	ecode = ntdb_oob(ntdb, off,
+			 frec_len(frec) + sizeof(struct ntdb_used_record),
+			 false);
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+	if (size_to_bucket(frec_len(frec)) != bucket) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: offset %llu in wrong bucket"
+				  " (%u vs %u)",
+				  (long long)off,
+				  bucket, size_to_bucket(frec_len(frec)));
+	}
+	if (prev && prev != frec_prev(frec)) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: offset %llu bad prev"
+				  " (%llu vs %llu)",
+				  (long long)off,
+				  (long long)prev, (long long)frec_len(frec));
+	}
+	return NTDB_SUCCESS;
+}
+
+static enum NTDB_ERROR check_free_table(struct ntdb_context *ntdb,
+				       ntdb_off_t ftable_off,
+				       unsigned ftable_num,
+				       ntdb_off_t fr[],
+				       size_t num_free,
+				       size_t *num_found)
+{
+	struct ntdb_freetable ft;
+	ntdb_off_t h;
+	unsigned int i;
+	enum NTDB_ERROR ecode;
+
+	ecode = ntdb_read_convert(ntdb, ftable_off, &ft, sizeof(ft));
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+
+	if (rec_magic(&ft.hdr) != NTDB_FTABLE_MAGIC
+	    || rec_key_length(&ft.hdr) != 0
+	    || rec_data_length(&ft.hdr) != sizeof(ft) - sizeof(ft.hdr)) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: Invalid header on free table");
+	}
+
+	for (i = 0; i < NTDB_FREE_BUCKETS; i++) {
+		ntdb_off_t off, prev = 0, *p, first = 0;
+		struct ntdb_free_record f;
+
+		h = bucket_off(ftable_off, i);
+		for (off = ntdb_read_off(ntdb, h); off; off = f.next) {
+			if (NTDB_OFF_IS_ERR(off)) {
+				return NTDB_OFF_TO_ERR(off);
+			}
+			if (!first) {
+				off &= NTDB_OFF_MASK;
+				first = off;
+			}
+			ecode = ntdb_read_convert(ntdb, off, &f, sizeof(f));
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+			ecode = check_free(ntdb, off, &f, prev, ftable_num, i);
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+
+			/* FIXME: Check hash bits */
+			p = asearch(&off, fr, num_free, off_cmp);
+			if (!p) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: Invalid offset"
+						  " %llu in free table",
+						  (long long)off);
+			}
+			/* Mark it invalid. */
+			*p ^= 1;
+			(*num_found)++;
+			prev = off;
+		}
+
+		if (first) {
+			/* Now we can check first back pointer. */
+			ecode = ntdb_read_convert(ntdb, first, &f, sizeof(f));
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+			ecode = check_free(ntdb, first, &f, prev, ftable_num, i);
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+		}
+	}
+	return NTDB_SUCCESS;
+}
+
+/* Slow, but should be very rare. */
+ntdb_off_t dead_space(struct ntdb_context *ntdb, ntdb_off_t off)
+{
+	size_t len;
+	enum NTDB_ERROR ecode;
+
+	for (len = 0; off + len < ntdb->file->map_size; len++) {
+		char c;
+		ecode = ntdb->io->tread(ntdb, off, &c, 1);
+		if (ecode != NTDB_SUCCESS) {
+			return NTDB_ERR_TO_OFF(ecode);
+		}
+		if (c != 0 && c != 0x43)
+			break;
+	}
+	return len;
+}
+
+static enum NTDB_ERROR check_linear(struct ntdb_context *ntdb,
+				   ntdb_off_t **used, size_t *num_used,
+				   ntdb_off_t **fr, size_t *num_free,
+				   uint64_t features, ntdb_off_t recovery)
+{
+	ntdb_off_t off;
+	ntdb_len_t len;
+	enum NTDB_ERROR ecode;
+	bool found_recovery = false;
+
+	for (off = sizeof(struct ntdb_header);
+	     off < ntdb->file->map_size;
+	     off += len) {
+		union {
+			struct ntdb_used_record u;
+			struct ntdb_free_record f;
+			struct ntdb_recovery_record r;
+		} rec;
+		/* r is larger: only get that if we need to. */
+		ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec.f));
+		if (ecode != NTDB_SUCCESS) {
+			return ecode;
+		}
+
+		/* If we crash after ftruncate, we can get zeroes or fill. */
+		if (rec.r.magic == NTDB_RECOVERY_INVALID_MAGIC
+		    || rec.r.magic ==  0x4343434343434343ULL) {
+			ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec.r));
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+			if (recovery == off) {
+				found_recovery = true;
+				len = sizeof(rec.r) + rec.r.max_len;
+			} else {
+				len = dead_space(ntdb, off);
+				if (NTDB_OFF_IS_ERR(len)) {
+					return NTDB_OFF_TO_ERR(len);
+				}
+				if (len < sizeof(rec.r)) {
+					return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+							  NTDB_LOG_ERROR,
+							  "ntdb_check: invalid"
+							  " dead space at %zu",
+							  (size_t)off);
+				}
+
+				ntdb_logerr(ntdb, NTDB_SUCCESS, NTDB_LOG_WARNING,
+					   "Dead space at %zu-%zu (of %zu)",
+					   (size_t)off, (size_t)(off + len),
+					   (size_t)ntdb->file->map_size);
+			}
+		} else if (rec.r.magic == NTDB_RECOVERY_MAGIC) {
+			ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec.r));
+			if (ecode != NTDB_SUCCESS) {
+				return ecode;
+			}
+			if (recovery != off) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: unexpected"
+						  " recovery record at offset"
+						  " %zu",
+						  (size_t)off);
+			}
+			if (rec.r.len > rec.r.max_len) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: invalid recovery"
+						  " length %zu",
+						  (size_t)rec.r.len);
+			}
+			if (rec.r.eof > ntdb->file->map_size) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: invalid old EOF"
+						  " %zu", (size_t)rec.r.eof);
+			}
+			found_recovery = true;
+			len = sizeof(rec.r) + rec.r.max_len;
+		} else if (frec_magic(&rec.f) == NTDB_FREE_MAGIC) {
+			len = sizeof(rec.u) + frec_len(&rec.f);
+			if (off + len > ntdb->file->map_size) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: free overlength"
+						  " %llu at offset %llu",
+						  (long long)len,
+						  (long long)off);
+			}
+			/* This record should be in free lists. */
+			if (frec_ftable(&rec.f) != NTDB_FTABLE_NONE
+			    && !append(ntdb, fr, num_free, off)) {
+				return ntdb_logerr(ntdb, NTDB_ERR_OOM,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: tracking %zu'th"
+						  " free record.", *num_free);
+			}
+		} else if (rec_magic(&rec.u) == NTDB_USED_MAGIC
+			   || rec_magic(&rec.u) == NTDB_CHAIN_MAGIC
+			   || rec_magic(&rec.u) == NTDB_HTABLE_MAGIC
+			   || rec_magic(&rec.u) == NTDB_FTABLE_MAGIC
+			   || rec_magic(&rec.u) == NTDB_CAP_MAGIC) {
+			uint64_t klen, dlen, extra;
+
+			/* This record is used! */
+			if (!append(ntdb, used, num_used, off)) {
+				return ntdb_logerr(ntdb, NTDB_ERR_OOM,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: tracking %zu'th"
+						  " used record.", *num_used);
+			}
+
+			klen = rec_key_length(&rec.u);
+			dlen = rec_data_length(&rec.u);
+			extra = rec_extra_padding(&rec.u);
+
+			len = sizeof(rec.u) + klen + dlen + extra;
+			if (off + len > ntdb->file->map_size) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: used overlength"
+						  " %llu at offset %llu",
+						  (long long)len,
+						  (long long)off);
+			}
+
+			if (len < sizeof(rec.f)) {
+				return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+						  NTDB_LOG_ERROR,
+						  "ntdb_check: too short record"
+						  " %llu at %llu",
+						  (long long)len,
+						  (long long)off);
+			}
+
+			/* Check that records have correct 0 at end (but may
+			 * not in future). */
+			if (extra && !features
+			    && rec_magic(&rec.u) != NTDB_CAP_MAGIC) {
+				const char *p;
+				char c;
+				p = ntdb_access_read(ntdb, off + sizeof(rec.u)
+						    + klen + dlen, 1, false);
+				if (NTDB_PTR_IS_ERR(p))
+					return NTDB_PTR_ERR(p);
+				c = *p;
+				ntdb_access_release(ntdb, p);
+
+				if (c != '\0') {
+					return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+							  NTDB_LOG_ERROR,
+							  "ntdb_check:"
+							  " non-zero extra"
+							  " at %llu",
+							  (long long)off);
+				}
+			}
+		} else {
+			return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT,
+					  NTDB_LOG_ERROR,
+					  "ntdb_check: Bad magic 0x%llx"
+					  " at offset %zu",
+					  (long long)rec_magic(&rec.u),
+					  (size_t)off);
+		}
+	}
+
+	/* We must have found recovery area if there was one. */
+	if (recovery != 0 && !found_recovery) {
+		return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				  "ntdb_check: expected a recovery area at %zu",
+				  (size_t)recovery);
+	}
+
+	return NTDB_SUCCESS;
+}
+
+_PUBLIC_ enum NTDB_ERROR ntdb_check_(struct ntdb_context *ntdb,
+			  enum NTDB_ERROR (*check)(NTDB_DATA, NTDB_DATA, void *),
+			  void *data)
+{
+	ntdb_off_t *fr = NULL, *used = NULL;
+	ntdb_off_t ft = 0, recovery = 0;
+	size_t num_free = 0, num_used = 0, num_found = 0, num_ftables = 0,
+		num_capabilities = 0;
+	uint64_t features = 0;
+	enum NTDB_ERROR ecode;
+
+	if (ntdb->flags & NTDB_CANT_CHECK) {
+		return ntdb_logerr(ntdb, NTDB_SUCCESS, NTDB_LOG_WARNING,
+				  "ntdb_check: database has unknown capability,"
+				  " cannot check.");
+	}
+
+	ecode = ntdb_allrecord_lock(ntdb, F_RDLCK, NTDB_LOCK_WAIT, false);
+	if (ecode != NTDB_SUCCESS) {
+		return ecode;
+	}
+
+	ecode = ntdb_lock_expand(ntdb, F_RDLCK);
+	if (ecode != NTDB_SUCCESS) {
+		ntdb_allrecord_unlock(ntdb, F_RDLCK);
+		return ecode;
+	}
+
+	ecode = check_header(ntdb, &recovery, &features, &num_capabilities);
+	if (ecode != NTDB_SUCCESS)
+		goto out;
+
+	/* First we do a linear scan, checking all records. */
+	ecode = check_linear(ntdb, &used, &num_used, &fr, &num_free, features,
+			     recovery);
+	if (ecode != NTDB_SUCCESS)
+		goto out;
+
+	for (ft = first_ftable(ntdb); ft; ft = next_ftable(ntdb, ft)) {
+		if (NTDB_OFF_IS_ERR(ft)) {
+			ecode = NTDB_OFF_TO_ERR(ft);
+			goto out;
+		}
+		ecode = check_free_table(ntdb, ft, num_ftables, fr, num_free,
+					 &num_found);
+		if (ecode != NTDB_SUCCESS)
+			goto out;
+		num_ftables++;
+	}
+
+	/* FIXME: Check key uniqueness? */
+	ecode = check_hash(ntdb, used, num_used, num_ftables + num_capabilities,
+			   check, data);
+	if (ecode != NTDB_SUCCESS)
+		goto out;
+
+	if (num_found != num_free) {
+		ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
+				   "ntdb_check: Not all entries are in"
+				   " free table");
+	}
+
+out:
+	ntdb_allrecord_unlock(ntdb, F_RDLCK);
+	ntdb_unlock_expand(ntdb, F_RDLCK);
+	ntdb->free_fn(fr, ntdb->alloc_data);
+	ntdb->free_fn(used, ntdb->alloc_data);
+	return ecode;
+}