text: // @file mongommf.cpp
  
  /**
  *    Copyright (C) 2010 10gen Inc.
  *
  *    This program is free software: you can redistribute it and/or  modify
  *    it under the terms of the GNU Affero General Public License, version 3,
  *    as published by the Free Software Foundation.
  *
  *    This program is distributed in the hope that it will be useful,
  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *    GNU Affero General Public License for more details.
  *
  *    You should have received a copy of the GNU Affero General Public License
  *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  /* this module adds some of our layers atop memory mapped files - specifically our handling of private views & such
     if you don't care about journaling/durability (temp sort files & such) use MemoryMappedFile class, not this.
  */
  
  #include "pch.h"
  #include "cmdline.h"
  #include "mongommf.h"
  #include "dur.h"
  #include "dur_journalformat.h"
  #include "../util/mongoutils/str.h"
  #include "mongomutex.h"
  #include "d_globals.h"
  #include "memconcept.h"
  #include "d_concurrency.h"
  
  using namespace mongoutils;
  
  namespace mongo {
  
      void MongoMMF::remapThePrivateView() {
          verify( cmdLine.dur );
  
          // todo 1.9 : it turns out we require that we always remap to the same address.
          // so the remove / add isn't necessary and can be removed?
          void *old = _view_private;
          //privateViews.remove(_view_private);        
          _view_private = remapPrivateView(_view_private);
          //privateViews.add(_view_private, this);
          fassert( 16112, _view_private == old );
      }
  
      /** register view. threadsafe */
      void PointerToMMF::add(void *view, MongoMMF *f) {
          verify(view);
          verify(f);
          mutex::scoped_lock lk(_m);
          _views.insert( pair<void*,MongoMMF*>(view,f) );
      }
  
      /** de-register view. threadsafe */
      void PointerToMMF::remove(void *view) {
          if( view ) {
              mutex::scoped_lock lk(_m);
              _views.erase(view);
          }
      }
  
      PointerToMMF::PointerToMMF() : _m("PointerToMMF") {
  #if defined(SIZE_MAX)
          size_t max = SIZE_MAX;
  #else
          size_t max = ~((size_t)0);
  #endif
          verify( max > (size_t) this ); // just checking that no one redef'd SIZE_MAX and that it is sane
  
          // this way we don't need any boundary checking in _find()
          _views.insert( pair<void*,MongoMMF*>((void*)0,(MongoMMF*)0) );
          _views.insert( pair<void*,MongoMMF*>((void*)max,(MongoMMF*)0) );
      }
  
      /** underscore version of find is for when you are already locked
          @param ofs out return our offset in the view
          @return the MongoMMF to which this pointer belongs
      */
      MongoMMF* PointerToMMF::find_inlock(void *p, /*out*/ size_t& ofs) {
          //
          // .................memory..........................
          //    v1       p                      v2
          //    [--------------------]          [-------]
          //
          // e.g., _find(p) == v1
          //
          const pair<void*,MongoMMF*> x = *(--_views.upper_bound(p));
          MongoMMF *mmf = x.second;
          if( mmf ) {
              size_t o = ((char *)p) - ((char*)x.first);
              if( o < mmf->length() ) {
                  ofs = o;
                  return mmf;
              }
          }
          return 0;
      }
  
      /** find associated MMF object for a given pointer.
          threadsafe
          @param ofs out returns offset into the view of the pointer, if found.
          @return the MongoMMF to which this pointer belongs. null if not found.
      */
      MongoMMF* PointerToMMF::find(void *p, /*out*/ size_t& ofs) {
          mutex::scoped_lock lk(_m);
          return find_inlock(p, ofs);
      }
  
      PointerToMMF privateViews;
  
      /* void* MongoMMF::switchToPrivateView(void *readonly_ptr) {
          verify( cmdLine.dur );
          verify( testIntent );
  
          void *p = readonly_ptr;
  
          {
              size_t ofs=0;
              MongoMMF *mmf = ourReadViews.find(p, ofs);
              if( mmf ) {
                  void *res = ((char *)mmf->_view_private) + ofs;
                  return res;
              }
          }
  
          {
              size_t ofs=0;
              MongoMMF *mmf = privateViews.find(p, ofs);
              if( mmf ) {
                  log() << "dur: perf warning p=" << p << " is already in the writable view of " << mmf->filename() << endl;
                  return p;
              }
          }
  
          // did you call writing() with a pointer that isn't into a datafile?
          log() << "dur error switchToPrivateView " << p << endl;
          return p;
      }*/
  
      /* switch to _view_write.  normally, this is a bad idea since your changes will not
         show up in _view_private if there have been changes there; thus the leading underscore
         as a tad of a "warning".  but useful when done with some care, such as during
         initialization.
      */
      void* MongoMMF::_switchToWritableView(void *p) {
          size_t ofs;
          MongoMMF *f = privateViews.find(p, ofs);
          verify( f );
          return (((char *)f->_view_write)+ofs);
      }
  
      extern string dbpath;
  
      // here so that it is precomputed...
      void MongoMMF::setPath(string f) {
          string suffix;
          string prefix;
          bool ok = str::rSplitOn(f, '.', prefix, suffix);
          uassert(13520, str::stream() << "MongoMMF only supports filenames in a certain format " << f, ok);
          if( suffix == "ns" )
              _fileSuffixNo = dur::JEntry::DotNsSuffix;
          else
              _fileSuffixNo = (int) str::toUnsigned(suffix);
  
          _p = RelativePath::fromFullPath(prefix);
      }
  
      bool MongoMMF::open(string fname, bool sequentialHint) {
          LOG(3) << "mmf open " << fname << endl;
          setPath(fname);
          _view_write = mapWithOptions(fname.c_str(), sequentialHint ? SEQUENTIAL : 0);
          return finishOpening();
      }
  
      bool MongoMMF::create(string fname, unsigned long long& len, bool sequentialHint) {
          LOG(3) << "mmf create " << fname << endl;
          setPath(fname);
          _view_write = map(fname.c_str(), len, sequentialHint ? SEQUENTIAL : 0);
          return finishOpening();
      }
  
      bool MongoMMF::finishOpening() {
          LOG(3) << "mmf finishOpening " << (void*) _view_write << ' ' << filename() << " len:" << length() << endl;
          if( _view_write ) {
              if( cmdLine.dur ) {
                  _view_private = createPrivateMap();
                  if( _view_private == 0 ) {
                      msgasserted(13636, str::stream() << "file " << filename() << " open/create failed in createPrivateMap (look in log for more information)");
                  }
                  privateViews.add(_view_private, this); // note that testIntent builds use this, even though it points to view_write then...
              }
              else {
                  _view_private = _view_write;
              }
              return true;
          }
          return false;
      }
  
      MongoMMF::MongoMMF() : _willNeedRemap(false) {
          _view_write = _view_private = 0;
      }
  
      MongoMMF::~MongoMMF() {
          try { 
              close();
          }
          catch(...) { error() << "exception in ~MongoMMF" << endl; }
      }
  
      namespace dur {
          void closingFileNotification();
      }
  
      /*virtual*/ void MongoMMF::close() {
          LOG(3) << "mmf close " << filename() << endl;
  
          if( view_write() /*actually was opened*/ ) {
              if( cmdLine.dur ) {
                  dur::closingFileNotification();
              }
  	    /* todo: is it ok to close files if we are not globally locked exclusively?
                       probably, but need to review. also note the lock assert below is
  		     rather vague and not checking if the right database is locked 
  	    */
              if( !Lock::somethingWriteLocked() ) { 
                  verify( inShutdown() );
                  DEV { 
                      log() << "is it really ok to close a mongommf outside a write lock? file:" << filename() << endl;
                  }
              }
          }
  
          LockMongoFilesExclusive lk;
          privateViews.remove(_view_private);
          memconcept::invalidate(_view_private);
          _view_write = _view_private = 0;
          MemoryMappedFile::close();
      }
  
  }
  