/** put the basic write operation into the buffer (bb) to be journaled */ static void prepBasicWrite_inlock(AlignedBuilder&bb, const WriteIntent *i, RelativePath& lastDbPath) { size_t ofs = 1; MongoMMF *mmf = findMMF_inlock(i->start(), /*out*/ofs); if( unlikely(!mmf->willNeedRemap()) ) { // tag this mmf as needed a remap of its private view later. // usually it will already be dirty/already set, so we do the if above first // to avoid possibility of cpu cache line contention mmf->willNeedRemap() = true; } // since we have already looked up the mmf, we go ahead and remember the write view location // so we don't have to find the MongoMMF again later in WRITETODATAFILES() // // this was for WRITETODATAFILES_Impl2 so commented out now // /* dassert( i->w_ptr == 0 ); i->w_ptr = ((char*)mmf->view_write()) + ofs; */ JEntry e; e.len = min(i->length(), (unsigned)(mmf->length() - ofs)); //dont write past end of file assert( ofs <= 0x80000000 ); e.ofs = (unsigned) ofs; e.setFileNo( mmf->fileSuffixNo() ); if( mmf->relativePath() == local ) { e.setLocalDbContextBit(); } else if( mmf->relativePath() != lastDbPath ) { lastDbPath = mmf->relativePath(); JDbContext c; bb.appendStruct(c); bb.appendStr(lastDbPath.toString()); } bb.appendStruct(e); #if defined(_EXPERIMENTAL) i->ofsInJournalBuffer = bb.len(); #endif bb.appendBuf(i->start(), e.len); if (unlikely(e.len != (unsigned)i->length())) { log() << "journal info splitting prepBasicWrite at boundary" << endl; // This only happens if we write to the last byte in a file and // the fist byte in another file that is mapped adjacently. I // think most OSs leave at least a one page gap between // mappings, but better to be safe. WriteIntent next ((char*)i->start() + e.len, i->length() - e.len); prepBasicWrite_inlock(bb, &next, lastDbPath); } }