From a0a4af7701613d9c1b88672ab8a8fae00088fc98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Wed, 28 Feb 2024 15:49:05 +0300
Subject: [PATCH] =?UTF-8?q?mdbx:=20=D0=B8=D1=81=D0=BF=D1=80=D0=B0=D0=B2?=
 =?UTF-8?q?=D0=BB=D0=B5=D0=BD=D0=B8=D0=B5=20`me=5Fdxb=5Fmmap.current=20>?=
 =?UTF-8?q?=20me=5Fdxb=5Fmmap.limit`=20=D0=B8=20=D1=81=D1=80=D0=B0=D0=B1?=
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Устранение упущения приводящего к нелогичной ситуации `me_dxb_mmap.curren > me_dxb_mmap.limit` при "дребезге" размера БД.
В текущем понимании, последствий кроме срабатывания assert-проверки нет, а вероятность проявления близка к нулю.
---
 src/core.c | 11 ++++++++++-
 src/osal.c |  3 ++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/core.c b/src/core.c
index d52eb95e..a6230dac 100644
--- a/src/core.c
+++ b/src/core.c
@@ -6195,6 +6195,7 @@ __cold static int dxb_resize(MDBX_env *const env, const pgno_t used_pgno,
 #endif /* MDBX_ENABLE_MADVISE */
 
   rc = osal_mresize(mresize_flags, &env->me_dxb_mmap, size_bytes, limit_bytes);
+  eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
 
 #if MDBX_ENABLE_MADVISE
   if (rc == MDBX_SUCCESS) {
@@ -6220,6 +6221,7 @@ __cold static int dxb_resize(MDBX_env *const env, const pgno_t used_pgno,
 
 bailout:
   if (rc == MDBX_SUCCESS) {
+    eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
     eASSERT(env, limit_bytes == env->me_dxb_mmap.limit);
     eASSERT(env, size_bytes <= env->me_dxb_mmap.filesize);
     if (mode == explicit_resize)
@@ -6250,6 +6252,7 @@ bailout:
               "present %" PRIuPTR " -> %" PRIuPTR ", "
               "limit %" PRIuPTR " -> %" PRIuPTR ", errcode %d",
               prev_size, size_bytes, prev_limit, limit_bytes, rc);
+      eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
     }
     if (!env->me_dxb_mmap.base) {
       env->me_flags |= MDBX_FATAL_ERROR;
@@ -9061,6 +9064,7 @@ static int txn_renew(MDBX_txn *txn, const unsigned flags) {
     const size_t used_bytes = pgno2bytes(env, txn->mt_next_pgno);
     const size_t required_bytes =
         (txn->mt_flags & MDBX_TXN_RDONLY) ? used_bytes : size_bytes;
+    eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
     if (unlikely(required_bytes > env->me_dxb_mmap.current)) {
       /* Размер БД (для пишущих транзакций) или используемых данных (для
        * читающих транзакций) больше предыдущего/текущего размера внутри
@@ -9078,6 +9082,7 @@ static int txn_renew(MDBX_txn *txn, const unsigned flags) {
                       txn->mt_geo.upper, implicit_grow);
       if (unlikely(rc != MDBX_SUCCESS))
         goto bailout;
+      eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
     } else if (unlikely(size_bytes < env->me_dxb_mmap.current)) {
       /* Размер БД меньше предыдущего/текущего размера внутри процесса, можно
        * уменьшить, но всё сложнее:
@@ -9103,11 +9108,15 @@ static int txn_renew(MDBX_txn *txn, const unsigned flags) {
       rc = osal_fastmutex_acquire(&env->me_remap_guard);
 #endif
       if (likely(rc == MDBX_SUCCESS)) {
+        eASSERT(env, env->me_dxb_mmap.limit >= env->me_dxb_mmap.current);
         rc = osal_filesize(env->me_dxb_mmap.fd, &env->me_dxb_mmap.filesize);
         if (likely(rc == MDBX_SUCCESS)) {
           eASSERT(env, env->me_dxb_mmap.filesize >= required_bytes);
           if (env->me_dxb_mmap.current > env->me_dxb_mmap.filesize)
-            env->me_dxb_mmap.current = (size_t)env->me_dxb_mmap.filesize;
+            env->me_dxb_mmap.current =
+                (env->me_dxb_mmap.limit < env->me_dxb_mmap.filesize)
+                    ? env->me_dxb_mmap.limit
+                    : (size_t)env->me_dxb_mmap.filesize;
         }
 #if defined(_WIN32) || defined(_WIN64)
         osal_srwlock_ReleaseShared(&env->me_remap_guard);
diff --git a/src/osal.c b/src/osal.c
index b07565b4..9844dd4f 100644
--- a/src/osal.c
+++ b/src/osal.c
@@ -2571,7 +2571,7 @@ retry_mapview:;
           ptr_disp(map->base, size),
           ((map->current < map->limit) ? map->current : map->limit) - size);
     }
-    map->current = size;
+    map->current = (size < map->limit) ? size : map->limit;
   }
 
   if (limit == map->limit)
@@ -2732,6 +2732,7 @@ retry_mapview:;
     map->base = ptr;
   }
   map->limit = limit;
+  map->current = size;
 
 #if MDBX_ENABLE_MADVISE
 #ifdef MADV_DONTFORK