mdbx: fix operation for unusual small/large system page size.

More for https://github.com/erthink/libmdbx/issues/157

Change-Id: I4f2ed54b50653d0375538b82c48590d1037cd93b

ChangeLog.md

@@ -46,6 +46,7 @@ New features:
     - a spilled pages, including overflow/large pages, now can be reused and refunded/compactified in nested transactions;
     - more effective refunding/compactification especially for the loosed page cache.
  - Added `MDBX_ENABLE_REFUND` and `MDBX_PNL_ASCENDING` internal/advanced build options.
+ - Added `mdbx_default_pagesize()` function.
 
 Fixes:
 
@@ -58,6 +59,7 @@ Fixes:
  - Fixed page leak in extra rare case the list of retired pages changed during update GC on transaction commit.
  - Fixed assertions to avoid false-positive UB detection by CLANG/LLVM (https://github.com/erthink/libmdbx/issues/153).
  - Fixed `MDBX_TXN_FULL` and regressive `MDBX_KEYEXIST` during large transaction commit with `MDBX_LIFORECLAIM` (https://github.com/erthink/libmdbx/issues/123).
+ - Fixed operation on systems with unusual small/large page size, including PowerPC (https://github.com/erthink/libmdbx/issues/157).
 
 
 ## v0.9.2 at 2020-11-27

mdbx.h

@@ -2852,6 +2852,12 @@ LIBMDBX_INLINE_API(int, mdbx_env_get_maxdbs,
   return rc;
 }
 
+/** \brief Returns the default size of database page for the current system.
+ * \ingroup c_statinfo
+ * \details Default size of database page depends on the size of the system
+ * page and usually exactly match it. */
+MDBX_NOTHROW_PURE_FUNCTION LIBMDBX_API size_t mdbx_default_pagesize(void);
+
 /** \brief Get the maximum size of keys can write.
  * \ingroup c_statinfo
  *

mdbx.h++

@@ -1838,7 +1838,9 @@ public:
   bool is_empty() const;
 
   /// \brief Returns default page size for current system/platform.
-  static size_t default_pagesize() noexcept;
+  static size_t default_pagesize() noexcept {
+    return ::mdbx_default_pagesize();
+  }
 
   struct limits {
     limits() = delete;

src/core.c

@@ -346,10 +346,18 @@ __cold int mdbx_env_get_maxkeysize_ex(const MDBX_env *env,
   return (int)mdbx_limits_keysize_max((intptr_t)env->me_psize, flags);
 }
 
+size_t mdbx_default_pagesize(void) {
+  size_t pagesize = mdbx_syspagesize();
+  mdbx_ensure(nullptr, is_powerof2(pagesize));
+  pagesize = (pagesize >= MIN_PAGESIZE) ? pagesize : MIN_PAGESIZE;
+  pagesize = (pagesize <= MAX_PAGESIZE) ? pagesize : MAX_PAGESIZE;
+  return pagesize;
+}
+
 __cold intptr_t mdbx_limits_keysize_max(intptr_t pagesize,
                                         MDBX_db_flags_t flags) {
   if (pagesize < 1)
-    pagesize = (intptr_t)mdbx_syspagesize();
+    pagesize = (intptr_t)mdbx_default_pagesize();
   if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
                pagesize > (intptr_t)MAX_PAGESIZE ||
                !is_powerof2((size_t)pagesize)))
@@ -383,7 +391,7 @@ __cold int mdbx_env_get_maxvalsize_ex(const MDBX_env *env,
 __cold intptr_t mdbx_limits_valsize_max(intptr_t pagesize,
                                         MDBX_db_flags_t flags) {
   if (pagesize < 1)
-    pagesize = (intptr_t)mdbx_syspagesize();
+    pagesize = (intptr_t)mdbx_default_pagesize();
   if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
                pagesize > (intptr_t)MAX_PAGESIZE ||
                !is_powerof2((size_t)pagesize)))
@@ -10004,7 +10012,8 @@ __cold int mdbx_env_create(MDBX_env **penv) {
     goto bailout;
   }
   env->me_os_psize = (unsigned)os_psize;
-  mdbx_setup_pagesize(env, env->me_os_psize);
+  mdbx_setup_pagesize(env, (env->me_os_psize < MAX_PAGESIZE) ? env->me_os_psize
+                                                             : MAX_PAGESIZE);
 
   rc = mdbx_fastmutex_init(&env->me_dbi_lock);
   if (unlikely(rc != MDBX_SUCCESS))
@@ -10969,12 +10978,14 @@ static __cold int mdbx_setup_lck(MDBX_env *env, char *lck_pathname,
 
   const size_t maxreaders =
       ((size_t)size - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader);
-  if (size > 65536 || maxreaders < 2 || maxreaders > MDBX_READERS_LIMIT) {
-    mdbx_error("lck-size too big (up to %" PRIuPTR " readers)", maxreaders);
+  if (maxreaders < 4) {
+    mdbx_error("lck-size too small (up to %" PRIuPTR " readers)", maxreaders);
     err = MDBX_PROBLEM;
     goto bailout;
   }
-  env->me_maxreaders = (unsigned)maxreaders;
+  env->me_maxreaders = (maxreaders <= MDBX_READERS_LIMIT)
+                           ? (unsigned)maxreaders
+                           : (unsigned)MDBX_READERS_LIMIT;
 
   err = mdbx_mmap((env->me_flags & MDBX_EXCLUSIVE) | MDBX_WRITEMAP,
                   &env->me_lck_mmap, (size_t)size, (size_t)size,
@@ -11388,7 +11399,8 @@ __cold int mdbx_env_delete(const char *pathname, MDBX_env_delete_mode_t mode) {
   memset(&dummy_env, 0, sizeof(dummy_env));
   dummy_env.me_flags =
       (mode == MDBX_ENV_ENSURE_UNUSED) ? MDBX_EXCLUSIVE : MDBX_ENV_DEFAULTS;
-  dummy_env.me_psize = dummy_env.me_os_psize = (unsigned)mdbx_syspagesize();
+  dummy_env.me_os_psize = (unsigned)mdbx_syspagesize();
+  dummy_env.me_psize = (unsigned)mdbx_default_pagesize();
   dummy_env.me_pathname = (char *)pathname;
 
   MDBX_handle_env_pathname env_pathname;
@@ -20119,7 +20131,7 @@ __cold MDBX_NOTHROW_CONST_FUNCTION intptr_t mdbx_limits_pgsize_max(void) {
 
 __cold intptr_t mdbx_limits_dbsize_min(intptr_t pagesize) {
   if (pagesize < 1)
-    pagesize = (intptr_t)mdbx_syspagesize();
+    pagesize = (intptr_t)mdbx_default_pagesize();
   else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
                     pagesize > (intptr_t)MAX_PAGESIZE ||
                     !is_powerof2((size_t)pagesize)))
@@ -20130,7 +20142,7 @@ __cold intptr_t mdbx_limits_dbsize_min(intptr_t pagesize) {
 
 __cold intptr_t mdbx_limits_dbsize_max(intptr_t pagesize) {
   if (pagesize < 1)
-    pagesize = (intptr_t)mdbx_syspagesize();
+    pagesize = (intptr_t)mdbx_default_pagesize();
   else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
                     pagesize > (intptr_t)MAX_PAGESIZE ||
                     !is_powerof2((size_t)pagesize)))
@@ -20144,7 +20156,7 @@ __cold intptr_t mdbx_limits_dbsize_max(intptr_t pagesize) {
 
 __cold intptr_t mdbx_limits_txnsize_max(intptr_t pagesize) {
   if (pagesize < 1)
-    pagesize = (intptr_t)mdbx_syspagesize();
+    pagesize = (intptr_t)mdbx_default_pagesize();
   else if (unlikely(pagesize < (intptr_t)MIN_PAGESIZE ||
                     pagesize > (intptr_t)MAX_PAGESIZE ||
                     !is_powerof2((size_t)pagesize)))

src/internals.h

@@ -628,7 +628,7 @@ typedef struct MDBX_lockinfo {
 #if MDBX_WORDBITS >= 64
 #define MAX_MAPSIZE MAX_MAPSIZE64
 #define MDBX_READERS_LIMIT                                                     \
-  ((65536 - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
+  ((MAX_PAGESIZE - sizeof(MDBX_lockinfo)) / sizeof(MDBX_reader))
 #define MDBX_PGL_LIMIT MAX_PAGENO
 #else
 #define MDBX_READERS_LIMIT 1024

src/mdbx.c++

@@ -985,8 +985,6 @@ template class LIBMDBX_API_TYPE buffer<polymorphic_allocator>;
 
 //------------------------------------------------------------------------------
 
-size_t env::default_pagesize() noexcept { return ::mdbx_syspagesize(); }
-
 static inline MDBX_env_flags_t mode2flags(env::mode mode) {
   switch (mode) {
   default: