libmdbx: fix for changing database size

1 files changed, 57 insertions, 16 deletions

diff --git a/libs/libmdbx/src/src/mdbx.c b/libs/libmdbx/src/src/mdbx.c
index 92e1b5c630..af03bdaa8d 100644
--- a/libs/libmdbx/src/src/mdbx.c
+++ b/libs/libmdbx/src/src/mdbx.c
@@ -1765,7 +1765,7 @@ static int mdbx_page_loose(MDBX_cursor *mc, MDBX_page *mp) {
       mdbx_kill_page(txn->mt_env, mp);
     mp->mp_flags = P_LOOSE | P_DIRTY;
     VALGRIND_MAKE_MEM_UNDEFINED(mp, PAGEHDRSZ);
-    VALGRIND_MAKE_MEM_DEFINED(&mp->mp_pgno, sizeof(pgno_t));
+    ASAN_UNPOISON_MEMORY_REGION(link, sizeof(*link));
     *link = txn->mt_loose_pages;
     txn->mt_loose_pages = mp;
     txn->mt_loose_count++;
@@ -2246,19 +2246,21 @@ static int mdbx_mapresize(MDBX_env *env, const pgno_t size_pgno,
       env->me_dxb_mmap.current == env->me_dxb_mmap.filesize)
     goto bailout;
 
-  if ((env->me_flags & MDBX_RDONLY) || limit_bytes != env->me_dxb_mmap.length ||
-      size_bytes < env->me_dxb_mmap.current) {
-    /* Windows allows only extending a read-write section, but not a
-     * corresponing mapped view. Therefore in other cases we must suspend
-     * the local threads for safe remap. */
-    array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
-    array_onstack.count = 0;
-    suspended = &array_onstack;
-    rc = mdbx_suspend_threads_before_remap(env, &suspended);
-    if (rc != MDBX_SUCCESS) {
-      mdbx_error("failed suspend-for-remap: errcode %d", rc);
-      goto bailout;
-    }
+  /* 1) Windows allows only extending a read-write section, but not a
+   *    corresponing mapped view. Therefore in other cases we must suspend
+   *    the local threads for safe remap.
+   * 2) At least on Windows 10 1803 the entire mapped section is unavailable
+   *    for short time during NtExtendSection() or VirtualAlloc() execution.
+   *
+   * THEREFORE LOCAL THREADS SUSPENDING IS ALWAYS REQUIRED!
+   */
+  array_onstack.limit = ARRAY_LENGTH(array_onstack.handles);
+  array_onstack.count = 0;
+  suspended = &array_onstack;
+  rc = mdbx_suspend_threads_before_remap(env, &suspended);
+  if (rc != MDBX_SUCCESS) {
+    mdbx_error("failed suspend-for-remap: errcode %d", rc);
+    goto bailout;
   }
 #else
   /* Acquire guard to avoid collision between read and write txns
@@ -3347,6 +3349,13 @@ static int mdbx_txn_renew0(MDBX_txn *txn, unsigned flags) {
       }
     }
     txn->mt_owner = mdbx_thread_self();
+#if defined(_WIN32) || defined(_WIN64)
+    if ((txn->mt_flags & MDBX_TXN_RDONLY) != 0 && size > env->me_dbgeo.lower &&
+        env->me_dbgeo.shrink) {
+      txn->mt_flags |= MDBX_SHRINK_ALLOWED;
+      mdbx_srwlock_AcquireShared(&env->me_remap_guard);
+    }
+#endif
     return MDBX_SUCCESS;
   }
 bailout:
@@ -3514,8 +3523,8 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
     if (txn != env->me_txn0)
       mdbx_free(txn);
   } else {
-    mdbx_assert(env,
-                (txn->mt_flags & ~(MDBX_TXN_RDONLY | MDBX_TXN_WRITEMAP)) == 0);
+    mdbx_assert(env, (txn->mt_flags & ~(MDBX_TXN_RDONLY | MDBX_TXN_WRITEMAP |
+                                        MDBX_SHRINK_ALLOWED)) == 0);
     txn->mt_signature = MDBX_MT_SIGNATURE;
     *ret = txn;
     mdbx_debug("begin txn %" PRIaTXN "%c %p on env %p, root page %" PRIaPGNO
@@ -3608,6 +3617,10 @@ static int mdbx_txn_end(MDBX_txn *txn, unsigned mode) {
              txn->mt_dbs[FREE_DBI].md_root);
 
   if (F_ISSET(txn->mt_flags, MDBX_TXN_RDONLY)) {
+#if defined(_WIN32) || defined(_WIN64)
+    if (txn->mt_flags & MDBX_SHRINK_ALLOWED)
+      mdbx_srwlock_ReleaseShared(&env->me_remap_guard);
+#endif
     if (txn->mt_ro_reader) {
       txn->mt_ro_reader->mr_txnid = ~(txnid_t)0;
       env->me_lck->mti_readers_refresh_flag = true;
@@ -5841,6 +5854,34 @@ LIBMDBX_API int mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower,
                 meta.mm_geo.shrink == bytes2pgno(env, env->me_dbgeo.shrink));
 
     if (memcmp(&meta.mm_geo, &head->mm_geo, sizeof(meta.mm_geo))) {
+
+#if defined(_WIN32) || defined(_WIN64)
+      /* Was DB shrinking disabled before and now it will be enabled? */
+      if (meta.mm_geo.lower < meta.mm_geo.upper && meta.mm_geo.shrink &&
+          !(head->mm_geo.lower < head->mm_geo.upper && head->mm_geo.shrink)) {
+        rc = mdbx_rdt_lock(env);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+
+        /* Check if there are any reading threads that do not use the SRWL */
+        const mdbx_pid_t CurrentTid = GetCurrentThreadId();
+        const MDBX_reader *const begin = env->me_lck->mti_readers;
+        const MDBX_reader *const end = begin + env->me_lck->mti_numreaders;
+        for (const MDBX_reader *reader = begin; reader < end; ++reader) {
+          if (reader->mr_pid == env->me_pid && reader->mr_tid &&
+              reader->mr_tid != CurrentTid) {
+            /* At least one thread may don't use SRWL */
+            rc = MDBX_EPERM;
+            break;
+          }
+        }
+
+        mdbx_rdt_unlock(env);
+        if (unlikely(rc != MDBX_SUCCESS))
+          goto bailout;
+      }
+#endif
+
       if (meta.mm_geo.now != head->mm_geo.now ||
           meta.mm_geo.upper != head->mm_geo.upper) {
         rc = mdbx_mapresize(env, meta.mm_geo.now, meta.mm_geo.upper);