tdb2: transaction support

[ccan] / ccan / tdb2 / lock.c

diff --git a/ccan/tdb2/lock.c b/ccan/tdb2/lock.c
index 60ed46379aa7b6960d51e5778c907945614b7c0f..a4cfd26c8c05da87540e0294aa2d9380ca7c4b5b 100644 (file)
--- a/ccan/tdb2/lock.c
+++ b/ccan/tdb2/lock.c
@@ -190,7 +190,6 @@ static int tdb_brunlock(struct tdb_context *tdb,
        return ret;
 }
 
-#if 0
 /*
   upgrade a read lock to a write lock. This needs to be handled in a
   special way as some OSes (such as solaris) have too conservative
@@ -217,8 +216,7 @@ int tdb_allrecord_upgrade(struct tdb_context *tdb)
        while (count--) {
                struct timeval tv;
                if (tdb_brlock(tdb, F_WRLCK,
-                              TDB_HASH_LOCK_START
-                              + (1ULL << tdb->header.v.hash_bits), 0,
+                              TDB_HASH_LOCK_START, 0,
                               TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
                        tdb->allrecord_lock.ltype = F_WRLCK;
                        tdb->allrecord_lock.off = 0;
@@ -236,7 +234,6 @@ int tdb_allrecord_upgrade(struct tdb_context *tdb)
                 "tdb_allrecord_upgrade failed\n");
        return -1;
 }
-#endif
 
 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
                                           tdb_off_t offset)
@@ -251,6 +248,27 @@ static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
        return NULL;
 }
 
+int tdb_lock_and_recover(struct tdb_context *tdb)
+{
+       int ret;
+
+       if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
+                              false) == -1) {
+               return -1;
+       }
+
+       if (tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK) == -1) {
+               tdb_allrecord_unlock(tdb, F_WRLCK);
+               return -1;
+       }
+       ret = tdb_transaction_recover(tdb);
+
+       tdb_unlock_open(tdb);
+       tdb_allrecord_unlock(tdb, F_WRLCK);
+
+       return ret;
+}
+
 /* lock an offset in the database. */
 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
                         enum tdb_lock_flags flags)
@@ -310,6 +328,21 @@ static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
                return -1;
        }
 
+       /* First time we grab a lock, perhaps someone died in commit? */
+       if (!(flags & TDB_LOCK_NOCHECK)
+           && tdb->num_lockrecs == 0
+           && unlikely(tdb_needs_recovery(tdb))) {
+               tdb_brunlock(tdb, ltype, offset, 1);
+
+               if (tdb_lock_and_recover(tdb) == -1) {
+                       return -1;
+               }
+
+               if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
+                       return -1;
+               }
+       }
+
        tdb->lockrecs[tdb->num_lockrecs].off = offset;
        tdb->lockrecs[tdb->num_lockrecs].count = 1;
        tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
@@ -318,40 +351,6 @@ static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
        return 0;
 }
 
-static int tdb_lock_and_recover(struct tdb_context *tdb)
-{
-#if 0 /* FIXME */
-
-       int ret;
-
-       /* We need to match locking order in transaction commit. */
-       if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {
-               return -1;
-       }
-
-       if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {
-               tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
-               return -1;
-       }
-
-       ret = tdb_transaction_recover(tdb);
-
-       tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);
-       tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
-
-       return ret;
-#else
-       abort();
-       return -1;
-#endif
-}
-
-static bool tdb_needs_recovery(struct tdb_context *tdb)
-{
-       /* FIXME */
-       return false;
-}
-
 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 {
        int ret = -1;
@@ -390,14 +389,12 @@ static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
        return ret;
 }
 
-#if 0
 /*
   get the transaction lock
  */
-int tdb_transaction_lock(struct tdb_context *tdb, int ltype,
-                        enum tdb_lock_flags lockflags)
+int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 {
-       return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags);
+       return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 }
 
 /*
@@ -405,9 +402,8 @@ int tdb_transaction_lock(struct tdb_context *tdb, int ltype,
  */
 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 {
-       return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
+       return tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
 }
-#endif
 
 /* We only need to lock individual bytes, but Linux merges consecutive locks
  * so we lock in contiguous ranges. */
@@ -474,7 +470,7 @@ int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
                return -1;
        }
 
-       if (tdb_has_locks(tdb)) {
+       if (tdb_has_hash_locks(tdb)) {
                /* can't combine global and chain locks */
                tdb->ecode = TDB_ERR_LOCK;
                tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
@@ -522,7 +518,7 @@ again:
        tdb->allrecord_lock.off = upgradable;
 
        /* Now check for needing recovery. */
-       if (unlikely(tdb_needs_recovery(tdb))) {
+       if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
                tdb_allrecord_unlock(tdb, ltype);
                if (tdb_lock_and_recover(tdb) == -1) {
                        return -1;
@@ -533,9 +529,9 @@ again:
        return 0;
 }
 
-int tdb_lock_open(struct tdb_context *tdb)
+int tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 {
-       return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT);
+       return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 }
 
 void tdb_unlock_open(struct tdb_context *tdb)
@@ -543,9 +539,16 @@ void tdb_unlock_open(struct tdb_context *tdb)
        tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 }
 
+bool tdb_has_open_lock(struct tdb_context *tdb)
+{
+       return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
+}
+
 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 {
-       return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype, TDB_LOCK_WAIT);
+       /* Lock doesn't protect data, so don't check (we recurse if we do!) */
+       return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
+                            TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 }
 
 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
@@ -598,9 +601,17 @@ bool tdb_has_expansion_lock(struct tdb_context *tdb)
        return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 }
 
-bool tdb_has_locks(struct tdb_context *tdb)
+bool tdb_has_hash_locks(struct tdb_context *tdb)
 {
-       return tdb->allrecord_lock.count || tdb->num_lockrecs;
+       unsigned int i;
+
+       for (i=0; i<tdb->num_lockrecs; i++) {
+               if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
+                   && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
+                                              + TDB_HASH_LOCK_RANGE))
+                       return true;
+       }
+       return false;
 }
 
 #if 0