tdb: cleanup: tdb_nest_lock/tdb_nest_unlock

Because fcntl locks don't nest, we track them in the tdb->lockrecs array
and only place/release them when the count goes to 1/0.  We only do this
for record locks, so we simply place the list number (or -1 for the free
list) in the structure.

To generalize this:

1) Put the offset rather than list number in struct tdb_lock_type.
2) Rename _tdb_lock() to tdb_nest_lock, make it non-static and move the
   allrecord check out to the callers (except the mark case which doesn't
   care).
3) Rename _tdb_unlock() to tdb_nest_unlock(), make it non-static and
   move the allrecord out to the callers (except mark again).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/lib/tdb/common/lock.c b/lib/tdb/common/lock.c
index 6b320f45fedf7a410bbed3ba5a14eff9f1fc3599..e3759a3f8dddd38465fa4da4fdaea992cecb264c 100644 (file)
--- a/lib/tdb/common/lock.c
+++ b/lib/tdb/common/lock.c
@@ -218,43 +218,38 @@ int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
        return -1;
 }
 
+/* list -1 is the alloc list, otherwise a hash chain. */
+static tdb_off_t lock_offset(int list)
+{
+       return FREELIST_TOP + 4*list;
+}
 
-/* lock a list in the database. list -1 is the alloc list */
-static int _tdb_lock(struct tdb_context *tdb, int list, int ltype,
-                    enum tdb_lock_flags flags)
+/* lock an offset in the database. */
+int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype,
+                 enum tdb_lock_flags flags)
 {
        struct tdb_lock_type *new_lck;
        int i;
 
-       /* 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;
-       }
-
-       if (tdb->allrecord_lock.count) {
-               tdb->ecode = TDB_ERR_LOCK;
-               return -1;
-       }
-
-       if (list < -1 || list >= (int)tdb->header.hash_size) {
+       if (offset >= lock_offset(tdb->header.hash_size)) {
                tdb->ecode = TDB_ERR_LOCK;
-               TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n", 
-                          list, ltype));
+               TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n",
+                        offset, ltype));
                return -1;
        }
        if (tdb->flags & TDB_NOLOCK)
                return 0;
 
        for (i=0; i<tdb->num_lockrecs; i++) {
-               if (tdb->lockrecs[i].list == list) {
+               if (tdb->lockrecs[i].off == offset) {
                        if (tdb->lockrecs[i].count == 0) {
                                /*
                                 * Can't happen, see tdb_unlock(). It should
                                 * be an assert.
                                 */
                                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: "
-                                        "lck->count == 0 for list %d", list));
+                                        "lck->count == 0 for offset %u",
+                                        offset));
                        }
                        /*
                         * Just increment the in-memory struct, posix locks
@@ -276,13 +271,13 @@ static int _tdb_lock(struct tdb_context *tdb, int list, int ltype,
 
        /* Since fcntl locks don't nest, we do a lock for the first one,
           and simply bump the count for future ones */
-       if (tdb->methods->brlock(tdb, ltype, FREELIST_TOP+4*list, 1, flags)) {
+       if (tdb->methods->brlock(tdb, ltype, offset, 1, flags)) {
                return -1;
        }
 
        tdb->num_locks++;
 
-       tdb->lockrecs[tdb->num_lockrecs].list = list;
+       tdb->lockrecs[tdb->num_lockrecs].off = offset;
        tdb->lockrecs[tdb->num_lockrecs].count = 1;
        tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
        tdb->num_lockrecs += 1;
@@ -295,7 +290,19 @@ int tdb_lock(struct tdb_context *tdb, int list, int ltype)
 {
        int ret;
 
-       ret = _tdb_lock(tdb, list, ltype, TDB_LOCK_WAIT);
+       /* 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;
+       }
+
+       if (tdb->allrecord_lock.count) {
+               tdb->ecode = TDB_ERR_LOCK;
+               ret = -1;
+       } else {
+               ret = tdb_nest_lock(tdb, lock_offset(list), ltype,
+                                   TDB_LOCK_WAIT);
+       }
        if (ret) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
                         "ltype=%d (%s)\n",  list, ltype, strerror(errno)));
@@ -306,18 +313,7 @@ int tdb_lock(struct tdb_context *tdb, int list, int ltype)
 /* lock a list in the database. list -1 is the alloc list. non-blocking lock */
 int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
 {
-       return _tdb_lock(tdb, list, ltype, TDB_LOCK_NOWAIT);
-}
-
-
-static int _tdb_unlock(struct tdb_context *tdb, int list, int ltype,
-                      bool mark_lock)
-{
-       int ret = -1;
-       int i;
-       struct tdb_lock_type *lck = NULL;
-
-       /* a global lock allows us to avoid per chain locks */
+       /* 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;
@@ -328,17 +324,28 @@ static int _tdb_unlock(struct tdb_context *tdb, int list, int ltype,
                return -1;
        }
 
+       return tdb_nest_lock(tdb, lock_offset(list), ltype, TDB_LOCK_NOWAIT);
+}
+
+
+int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype,
+                   bool mark_lock)
+{
+       int ret = -1;
+       int i;
+       struct tdb_lock_type *lck = NULL;
+
        if (tdb->flags & TDB_NOLOCK)
                return 0;
 
        /* Sanity checks */
-       if (list < -1 || list >= (int)tdb->header.hash_size) {
-               TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
+       if (offset >= lock_offset(tdb->header.hash_size)) {
+               TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->header.hash_size));
                return ret;
        }
 
        for (i=0; i<tdb->num_lockrecs; i++) {
-               if (tdb->lockrecs[i].list == list) {
+               if (tdb->lockrecs[i].off == offset) {
                        lck = &tdb->lockrecs[i];
                        break;
                }
@@ -364,8 +371,7 @@ static int _tdb_unlock(struct tdb_context *tdb, int list, int ltype,
        if (mark_lock) {
                ret = 0;
        } else {
-               ret = tdb->methods->brunlock(tdb, ltype,
-                                            FREELIST_TOP+4*list, 1);
+               ret = tdb->methods->brunlock(tdb, ltype, offset, 1);
        }
        tdb->num_locks--;
 
@@ -395,7 +401,18 @@ static int _tdb_unlock(struct tdb_context *tdb, int list, int ltype,
 
 int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
 {
-       return _tdb_unlock(tdb, list, ltype, false);
+       /* a global lock allows us to avoid per chain locks */
+       if (tdb->allrecord_lock.count &&
+           (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
+               return 0;
+       }
+
+       if (tdb->allrecord_lock.count) {
+               tdb->ecode = TDB_ERR_LOCK;
+               return -1;
+       }
+
+       return tdb_nest_unlock(tdb, lock_offset(list), ltype, false);
 }
 
 /*
@@ -599,8 +616,8 @@ int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
 /* mark a chain as locked without actually locking it. Warning! use with great caution! */
 int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
 {
-       int ret = _tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK,
-                           TDB_LOCK_MARK_ONLY);
+       int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
+                               F_WRLCK, TDB_LOCK_MARK_ONLY);
        tdb_trace_1rec(tdb, "tdb_chainlock_mark", key);
        return ret;
 }
@@ -609,7 +626,8 @@ int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
 int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
 {
        tdb_trace_1rec(tdb, "tdb_chainlock_unmark", key);
-       return _tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK, true);
+       return tdb_nest_unlock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
+                              F_WRLCK, true);
 }
 
 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)

diff --git a/lib/tdb/common/tdb_private.h b/lib/tdb/common/tdb_private.h
index 2e5679690f32146fbefe87e1299920944bb381ea..4e4816bd4aa7aadbbf7e1c412fd99d15ec267855 100644 (file)
--- a/lib/tdb/common/tdb_private.h
+++ b/lib/tdb/common/tdb_private.h
@@ -151,7 +151,7 @@ struct tdb_header {
 };
 
 struct tdb_lock_type {
-       int list;
+       uint32_t off;
        uint32_t count;
        uint32_t ltype;
 };
@@ -224,6 +224,10 @@ int tdb_munmap(struct tdb_context *tdb);
 void tdb_mmap(struct tdb_context *tdb);
 int tdb_lock(struct tdb_context *tdb, int list, int ltype);
 int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype);
+int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype,
+                 enum tdb_lock_flags flags);
+int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype,
+                   bool mark_lock);
 int tdb_unlock(struct tdb_context *tdb, int list, int ltype);
 int tdb_brlock(struct tdb_context *tdb,
               int rw_type, tdb_off_t offset, size_t len,

diff --git a/lib/tdb/common/transaction.c b/lib/tdb/common/transaction.c
index e72eff5b1f94d7da96d4ee20bc21e31b93038737..374c597d8debf064908ce56f722290edd351d735 100644 (file)
--- a/lib/tdb/common/transaction.c
+++ b/lib/tdb/common/transaction.c
@@ -631,7 +631,7 @@ static int _tdb_transaction_cancel(struct tdb_context *tdb, int ltype)
        if (tdb->num_locks != 0) {
                for (i=0;i<tdb->num_lockrecs;i++) {
                        tdb_brunlock(tdb, tdb->lockrecs[i].ltype,
-                                    FREELIST_TOP+4*tdb->lockrecs[i].list, 1);
+                                    tdb->lockrecs[i].off, 1);
                }
                tdb->num_locks = 0;
                tdb->num_lockrecs = 0;