From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 26 Aug 2010 10:27:56 +0000 (+0930)
Subject: tdb2: now we can store a key!
X-Git-Url: http://git.ozlabs.org/?p=ccan;a=commitdiff_plain;h=4916bc0a12ede1bf81c6895be9e7df39199f3290

tdb2: now we can store a key!
---

diff --git a/ccan/tdb2/free.c b/ccan/tdb2/free.c
index e486dcb7..134c1ff0 100644
--- a/ccan/tdb2/free.c
+++ b/ccan/tdb2/free.c
@@ -130,7 +130,7 @@ tdb_off_t zone_of(struct tdb_context *tdb, tdb_off_t off)
 	return off >> tdb->header.v.zone_bits;
 }
 
-/* Returns fl->max_bucket + 1, or list number to search. */
+/* Returns free_buckets + 1, or list number to search. */
 static tdb_off_t find_free_head(struct tdb_context *tdb, tdb_off_t bucket)
 {
 	tdb_off_t first, off;
@@ -138,7 +138,7 @@ static tdb_off_t find_free_head(struct tdb_context *tdb, tdb_off_t bucket)
 	/* Speculatively search for a non-zero bucket. */
 	first = tdb->last_zone * (tdb->header.v.free_buckets+1) + bucket;
 	off = tdb_find_nonzero_off(tdb, free_list_off(tdb, first),
-				   tdb->header.v.free_buckets - bucket);
+				   tdb->header.v.free_buckets + 1 - bucket);
 	return bucket + off;
 }
 
@@ -210,7 +210,7 @@ int add_free_record(struct tdb_context *tdb,
 	tdb->last_zone = zone_of(tdb, off);
 	list = tdb->last_zone * (tdb->header.v.free_buckets+1)
 		+ size_to_bucket(tdb, new.data_len);
-		
+
 	if (tdb_lock_free_list(tdb, list, TDB_LOCK_WAIT) != 0)
 		return -1;
 
@@ -319,7 +319,7 @@ static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 				tdb_len_t *actual)
 {
 	tdb_off_t list;
-	tdb_off_t off, prev, best_off;
+	tdb_off_t off, best_off;
 	struct tdb_free_record pad, best = { 0 }, *r;
 	double multiplier;
 
@@ -331,27 +331,21 @@ again:
 		return TDB_OFF_ERR;
 	}
 
-	prev = free_list_off(tdb, list);
-	off = tdb_read_off(tdb, prev);
-
-	if (unlikely(off == TDB_OFF_ERR))
-		goto unlock_err;
-
 	best.data_len = -1ULL;
 	best_off = 0;
 	multiplier = 1.0;
 
 	/* Walk the list to see if any are large enough, getting less fussy
 	 * as we go. */
-	while (off) {
-		prev = off;
-		off = tdb_read_off(tdb, prev);
-		if (unlikely(off == TDB_OFF_ERR))
-			goto unlock_err;
+	off = tdb_read_off(tdb, free_list_off(tdb, list));
+	if (unlikely(off == TDB_OFF_ERR))
+		goto unlock_err;
 
+	while (off) {
 		r = tdb_get(tdb, off, &pad, sizeof(*r));
 		if (!r)
 			goto unlock_err;
+
 		if (r->magic != TDB_FREE_MAGIC) {
 			tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 				 "lock_and_alloc: %llu non-free 0x%llx\n",
@@ -364,18 +358,9 @@ again:
 			best = *r;
 		}
 
-		if (best.data_len < size * multiplier && best_off) {
-			/* We're happy with this size: take it. */
-			if (remove_from_list(tdb, list, &best) != 0)
-				goto unlock_err;
-			tdb_unlock_free_list(tdb, list);
+		if (best.data_len < size * multiplier && best_off)
+			goto use_best;
 
-			if (to_used_record(tdb, best_off, size, best.data_len,
-					   actual)) {
-				return -1;
-			}
-			return best_off;
-		}
 		multiplier *= 1.01;
 
 		/* Since we're going slow anyway, try coalescing here. */
@@ -387,6 +372,22 @@ again:
 			/* This has unlocked list, restart. */
 			goto again;
 		}
+		off = r->next;
+	}
+
+	/* If we found anything at all, use it. */
+	if (best_off) {
+	use_best:
+		/* We're happy with this size: take it. */
+		if (remove_from_list(tdb, list, &best) != 0)
+			goto unlock_err;
+		tdb_unlock_free_list(tdb, list);
+
+		if (to_used_record(tdb, best_off, size, best.data_len,
+				   actual)) {
+			return -1;
+		}
+		return best_off;
 	}
 
 	tdb_unlock_free_list(tdb, list);
@@ -440,11 +441,11 @@ static tdb_off_t get_free(struct tdb_context *tdb, size_t size,
 		tdb_off_t b;
 
 		/* Start at exact size bucket, and search up... */
-		for (b = bucket; b <= tdb->header.v.num_zones; b++) {
+		for (b = bucket; b <= tdb->header.v.free_buckets; b++) {
 			b = find_free_head(tdb, b);
 
 			/* Non-empty list?  Try getting block. */
-			if (b <= tdb->header.v.num_zones) {
+			if (b <= tdb->header.v.free_buckets) {
 				/* Try getting one from list. */
 				off = lock_and_alloc(tdb, b, size, actual);
 				if (off == TDB_OFF_ERR)
@@ -698,7 +699,6 @@ int tdb_expand(struct tdb_context *tdb, tdb_len_t klen, tdb_len_t dlen,
 		}
 	}
 
-
 	/* Free up the old free buckets. */
 	old_free_off -= sizeof(fhdr);
 	if (tdb_read_convert(tdb, old_free_off, &fhdr, sizeof(fhdr)) == -1)
@@ -714,6 +714,8 @@ int tdb_expand(struct tdb_context *tdb, tdb_len_t klen, tdb_len_t dlen,
 	/* Start allocating from where the new space is. */
 	tdb->last_zone = zone_of(tdb, tdb->map_size - add);
 	tdb_access_release(tdb, oldf);
+	if (write_header(tdb) == -1)
+		goto fail;
 success:
 	tdb_allrecord_unlock(tdb, F_WRLCK);
 	return 0;
diff --git a/ccan/tdb2/lock.c b/ccan/tdb2/lock.c
index 96815f26..3230b25e 100644
--- a/ccan/tdb2/lock.c
+++ b/ccan/tdb2/lock.c
@@ -502,7 +502,7 @@ again:
 	tdb->allrecord_lock.off = upgradable;
 
 	/* Now we re-check header, holding lock. */
-	if (unlikely(update_header(tdb))) {
+	if (unlikely(header_changed(tdb))) {
 		tdb_allrecord_unlock(tdb, ltype);
 		goto again;
 	}
@@ -625,13 +625,18 @@ int tdb_unlockall_read(struct tdb_context *tdb)
 }
 #endif
 
-int tdb_lock_list(struct tdb_context *tdb, tdb_off_t list,
-		  int ltype, enum tdb_lock_flags waitflag)
+/* Returns the list we actually locked. */
+tdb_off_t tdb_lock_list(struct tdb_context *tdb, uint64_t hash,
+			int ltype, enum tdb_lock_flags waitflag)
 {
+	tdb_off_t list = hash & ((1ULL << tdb->header.v.hash_bits) - 1);
+	/* Header can change ONLY if we had no locks before. */
+	bool can_change = tdb->num_lockrecs == 0;
+
 	/* a allrecord lock allows us to avoid per chain locks */
 	if (tdb->allrecord_lock.count &&
 	    (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
-		return 0;
+		return list;
 	}
 
 	if (tdb->allrecord_lock.count) {
@@ -640,11 +645,22 @@ int tdb_lock_list(struct tdb_context *tdb, tdb_off_t list,
 			 "tdb_lock_list: have %s allrecordlock\n",
 			 tdb->allrecord_lock.ltype == F_RDLCK
 			 ? "read" : "write");
-		return -1;
+		return TDB_OFF_ERR;
 	}
 
-	/* FIXME: Should we do header_uptodate and return retry here? */
-	return tdb_nest_lock(tdb, TDB_HASH_LOCK_START + list, ltype, waitflag);
+again:
+	if (tdb_nest_lock(tdb, TDB_HASH_LOCK_START + list, ltype, waitflag))
+		return TDB_OFF_ERR;
+
+	if (can_change && unlikely(header_changed(tdb))) {
+		tdb_off_t new = hash & ((1ULL << tdb->header.v.hash_bits) - 1);
+		if (new != list) {
+			tdb_nest_unlock(tdb, TDB_HASH_LOCK_START+list, ltype);
+			list = new;
+			goto again;
+		}
+	}
+	return list;
 }
 
 int tdb_unlock_list(struct tdb_context *tdb, tdb_off_t list, int ltype)
@@ -702,23 +718,14 @@ void tdb_unlock_free_list(struct tdb_context *tdb, tdb_off_t flist)
 }
 
 #if 0
-static int chainlock_loop(struct tdb_context *tdb, const TDB_DATA *key,
-			  int ltype, enum tdb_lock_flags waitflag,
-			  const char *func)
+static int chainlock(struct tdb_context *tdb, const TDB_DATA *key,
+		     int ltype, enum tdb_lock_flags waitflag,
+		     const char *func)
 {
 	int ret;
 	uint64_t h = tdb_hash(tdb, key->dptr, key->dsize);
 
-again:
-	ret = tdb_lock_list(tdb,
-			    h & ((1ULL << tdb->header.v.hash_bits) - 1),
-			    ltype, waitflag);
-	if (likely(ret == 0) && unlikely(update_header(tdb))) {
-		tdb_unlock_list(tdb, h & ((1ULL << tdb->header.v.hash_bits)-1),
-				ltype);
-		goto again;
-	}
-
+	ret = tdb_lock_list(tdb, h, ltype, waitflag) == TDB_OFF_ERR ? -1 : 0;
 	tdb_trace_1rec(tdb, func, *key);
 	return ret;
 }
@@ -727,8 +734,7 @@ again:
    contention - it cannot guarantee how many records will be locked */
 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
 {
-	return chainlock_loop(tdb, &key, F_WRLCK, TDB_LOCK_WAIT,
-			      "tdb_chainlock");
+	return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_WAIT, "tdb_chainlock");
 }
 
 /* lock/unlock one hash chain, non-blocking. This is meant to be used
@@ -736,8 +742,8 @@ int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
    locked */
 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
 {
-	return chainlock_loop(tdb, &key, F_WRLCK, TDB_LOCK_NOWAIT,
-			      "tdb_chainlock_nonblock");
+	return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_NOWAIT,
+			 "tdb_chainlock_nonblock");
 }
 
 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
@@ -750,8 +756,8 @@ int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
 
 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
 {
-	return chainlock_loop(tdb, &key, F_RDLCK, TDB_LOCK_WAIT,
-			      "tdb_chainlock_read");
+	return chainlock(tdb, &key, F_RDLCK, TDB_LOCK_WAIT,
+			 "tdb_chainlock_read");
 }
 
 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
diff --git a/ccan/tdb2/private.h b/ccan/tdb2/private.h
index c743067a..86cfd777 100644
--- a/ccan/tdb2/private.h
+++ b/ccan/tdb2/private.h
@@ -136,7 +136,7 @@ static inline uint64_t rec_extra_padding(const struct tdb_used_record *r)
 
 static inline uint64_t rec_hash(const struct tdb_used_record *r)
 {
-	return ((r->magic_and_meta >> 32) & ((1ULL << 11) - 1)) << (64 - 11);
+	return ((r->magic_and_meta >> 32) & ((1ULL << 11) - 1));
 }
 
 static inline uint16_t rec_magic(const struct tdb_used_record *r)
@@ -254,8 +254,11 @@ struct tdb_methods {
   internal prototypes
 */
 /* tdb.c: */
-/* Returns true if header changed. */
-bool update_header(struct tdb_context *tdb);
+/* Returns true if header changed (and updates it). */
+bool header_changed(struct tdb_context *tdb);
+
+/* Commit header to disk. */
+int write_header(struct tdb_context *tdb);
 
 /* Hash random memory. */
 uint64_t tdb_hash(struct tdb_context *tdb, const void *ptr, size_t len);
@@ -349,8 +352,8 @@ uint64_t hash_record(struct tdb_context *tdb, tdb_off_t off);
 void tdb_lock_init(struct tdb_context *tdb);
 
 /* Lock/unlock a particular hash list. */
-int tdb_lock_list(struct tdb_context *tdb, tdb_off_t list,
-		  int ltype, enum tdb_lock_flags waitflag);
+tdb_off_t tdb_lock_list(struct tdb_context *tdb, uint64_t hash,
+			int ltype, enum tdb_lock_flags waitflag);
 int tdb_unlock_list(struct tdb_context *tdb, tdb_off_t list, int ltype);
 
 /* Lock/unlock a particular free list. */
diff --git a/ccan/tdb2/tdb.c b/ccan/tdb2/tdb.c
index 5d69eedc..2a89e36a 100644
--- a/ccan/tdb2/tdb.c
+++ b/ccan/tdb2/tdb.c
@@ -21,9 +21,9 @@ null_log_fn(struct tdb_context *tdb,
 /* We do a lot of work assuming our copy of the header volatile area
  * is uptodate, and usually it is.  However, once we grab a lock, we have to
  * re-check it. */
-bool update_header(struct tdb_context *tdb)
+bool header_changed(struct tdb_context *tdb)
 {
-	struct tdb_header_volatile pad, *v;
+	uint64_t gen;
 
 	if (!(tdb->flags & TDB_NOLOCK) && tdb->header_uptodate) {
 		tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
@@ -33,17 +33,23 @@ bool update_header(struct tdb_context *tdb)
 	/* We could get a partial update if we're not holding any locks. */
 	assert((tdb->flags & TDB_NOLOCK) || tdb_has_locks(tdb));
 
-	v = tdb_get(tdb, offsetof(struct tdb_header, v), &pad, sizeof(*v));
-	if (!v) {
-		/* On failure, imply we updated header so they retry. */
-		return true;
-	}
 	tdb->header_uptodate = true;
-	if (likely(memcmp(&tdb->header.v, v, sizeof(*v)) == 0)) {
-		return false;
+	gen = tdb_read_off(tdb, offsetof(struct tdb_header, v.generation));
+	if (unlikely(gen != tdb->header.v.generation)) {
+		tdb_read_convert(tdb, offsetof(struct tdb_header, v),
+				 &tdb->header.v, sizeof(tdb->header.v));
+		return true;
 	}
-	tdb->header.v = *v;
-	return true;
+	return false;
+}
+
+int write_header(struct tdb_context *tdb)
+{
+	assert(tdb_read_off(tdb, offsetof(struct tdb_header, v.generation))
+	       == tdb->header.v.generation);
+	tdb->header.v.generation++;
+	return tdb_write_convert(tdb, offsetof(struct tdb_header, v),
+				 &tdb->header.v, sizeof(tdb->header.v));
 }
 
 static uint64_t jenkins_hash(const void *key, size_t length, uint64_t seed,
@@ -382,10 +388,12 @@ static int tdb_key_compare(TDB_DATA key, TDB_DATA data, void *private_data)
 static void unlock_lists(struct tdb_context *tdb,
 			 uint64_t start, uint64_t end, int ltype)
 {
-	do {
+	for (;;) {
 		tdb_unlock_list(tdb, start, ltype);
+		if (start == end)
+			return;
 		start = (start + 1) & ((1ULL << tdb->header.v.hash_bits) - 1);
-	} while (start != end);
+	}
 }
 
 /* FIXME: Return header copy? */
@@ -402,26 +410,19 @@ static tdb_off_t find_bucket_and_lock(struct tdb_context *tdb,
 	uint64_t hextra;
 	tdb_off_t off;
 
-	/* hash_bits might be out of date... */
-again:
-	*start = *end = hash & ((1ULL << tdb->header.v.hash_bits) - 1);
-	hextra = hash >> tdb->header.v.hash_bits;
-
 	/* FIXME: can we avoid locks for some fast paths? */
-	if (tdb_lock_list(tdb, *end, ltype, TDB_LOCK_WAIT) == -1)
+	*start = tdb_lock_list(tdb, hash, ltype, TDB_LOCK_WAIT);
+	if (*start == TDB_OFF_ERR)
 		return TDB_OFF_ERR;
 
-	/* We only need to check this for first lock. */
-	if (unlikely(update_header(tdb))) {
-		tdb_unlock_list(tdb, *end, ltype);
-		goto again;
-	}
+	*end = *start;
+	hextra = hash >> tdb->header.v.hash_bits;
 
 	while ((off = tdb_read_off(tdb, tdb->header.v.hash_off
 				   + *end * sizeof(tdb_off_t)))
 	       != TDB_OFF_ERR) {
 		struct tdb_used_record pad, *r;
-		uint64_t keylen, next;
+		uint64_t keylen;
 
 		/* Didn't find it? */
 		if (!off)
@@ -470,16 +471,10 @@ again:
 	lock_next:
 		/* Lock next bucket. */
 		/* FIXME: We can deadlock if this wraps! */
-		next = (*end + 1) & ((1ULL << tdb->header.v.hash_bits) - 1);
-		if (next == *start) {
-			tdb->ecode = TDB_ERR_CORRUPT;
-			tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
-				 "find_bucket_and_lock: full hash table!\n");
+		off = tdb_lock_list(tdb, ++hash, ltype, TDB_LOCK_WAIT);
+		if (off == TDB_OFF_ERR)
 			goto unlock_err;
-		}
-		if (tdb_lock_list(tdb, next, ltype, TDB_LOCK_WAIT) == -1)
-			goto unlock_err;
-		*end = next;
+		*end = off;
 	}
 
 unlock_err:
@@ -514,11 +509,9 @@ static void enlarge_hash(struct tdb_context *tdb)
 	if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false) == -1)
 		return;
 
-	if (unlikely(update_header(tdb))) {
-		/* Someone else enlarged for us?  Nothing to do. */
-		if ((1ULL << tdb->header.v.hash_bits) != num)
-			goto unlock;
-	}
+	/* Someone else enlarged for us?  Nothing to do. */
+	if ((1ULL << tdb->header.v.hash_bits) != num)
+		goto unlock;
 
 	newoff = alloc(tdb, 0, num * 2, 0, false);
 	if (unlikely(newoff == TDB_OFF_ERR))
@@ -728,7 +721,8 @@ again:
 	num++;
 
 	for (i = chain + 1; i < chain + 1 + num; i++) {
-		if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_WAIT) == -1) {
+		if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_WAIT)
+		    == TDB_OFF_ERR) {
 			if (i != chain + 1)
 				unlock_lists(tdb, chain + 1, i-1, F_WRLCK);
 			return -1;
@@ -741,7 +735,8 @@ again:
 						 1ULL << tdb->header.v.hash_bits);
 		(*extra_locks)++;
 		for (i = 0; i < *extra_locks; i++) {
-			if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_NOWAIT)) {
+			if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_NOWAIT)
+			    == TDB_OFF_ERR) {
 				/* Failed.  Caller must lock in order. */
 				if (i)
 					unlock_lists(tdb, 0, i-1, F_WRLCK);
@@ -827,7 +822,8 @@ int tdb_delete(struct tdb_context *tdb, struct tdb_data key)
 
 		/* We need extra locks at the start. */
 		for (i = 0; i < extra_locks; i++) {
-			if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_WAIT)) {
+			if (tdb_lock_list(tdb, i, F_WRLCK, TDB_LOCK_WAIT)
+			    == TDB_OFF_ERR) {
 				if (i)
 					unlock_lists(tdb, 0, i-1, F_WRLCK);
 				return -1;
diff --git a/ccan/tdb2/test/run-encode.c b/ccan/tdb2/test/run-encode.c
index aa2ec51a..b8c24366 100644
--- a/ccan/tdb2/test/run-encode.c
+++ b/ccan/tdb2/test/run-encode.c
@@ -34,7 +34,7 @@ int main(int argc, char *argv[])
 		ok1(rec_key_length(&rec) == klen);
 		ok1(rec_data_length(&rec) == dlen);
 		ok1(rec_extra_padding(&rec) == xlen);
-		ok1(rec_hash(&rec) == h);
+		ok1(rec_hash(&rec) << (64 - 11) == h);
 		ok1(rec_magic(&rec) == TDB_MAGIC);
 	}
 	ok1(tap_log_messages == 0);
diff --git a/ccan/tdb2/test/run-simple-store.c b/ccan/tdb2/test/run-simple-store.c
new file mode 100644
index 00000000..44ac9071
--- /dev/null
+++ b/ccan/tdb2/test/run-simple-store.c
@@ -0,0 +1,41 @@
+#include <ccan/tdb2/tdb.c>
+#include <ccan/tdb2/free.c>
+#include <ccan/tdb2/lock.c>
+#include <ccan/tdb2/io.c>
+#include <ccan/tdb2/check.c>
+#include <ccan/tap/tap.h>
+#include "logging.h"
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct tdb_context *tdb;
+	int flags[] = { TDB_INTERNAL, TDB_DEFAULT,
+			TDB_INTERNAL|TDB_CONVERT, TDB_CONVERT };
+	struct tdb_data key = { (unsigned char *)"key", 3 };
+	struct tdb_data data = { (unsigned char *)"data", 4 };
+
+	plan_tests(sizeof(flags) / sizeof(flags[0]) * 9 + 1);
+	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
+		tdb = tdb_open("/tmp/run-new_database.tdb", flags[i],
+			       O_RDWR|O_CREAT|O_TRUNC, 0600, NULL);
+		tdb->log = tap_log_fn;
+		ok1(tdb);
+		if (tdb) {
+			/* Modify should fail. */
+			ok1(tdb_store(tdb, key, data, TDB_MODIFY) == -1);
+			ok1(tdb_error(tdb) == TDB_ERR_NOEXIST);
+			ok1(tdb_check(tdb, NULL, NULL) == 0);
+			/* Insert should succeed. */
+			ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+			ok1(tdb_check(tdb, NULL, NULL) == 0);
+			/* Second insert should fail. */
+			ok1(tdb_store(tdb, key, data, TDB_INSERT) == -1);
+			ok1(tdb_error(tdb) == TDB_ERR_EXISTS);
+			ok1(tdb_check(tdb, NULL, NULL) == 0);
+			tdb_close(tdb);
+		}
+	}
+	ok1(tap_log_messages == 0);
+	return exit_status();
+}