mmap_posix.cpp

// mmap_posix.cpp

/**
 *    Copyright (C) 2008 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/>.
 */

#include "stdafx.h"
#include "mmap.h"

#include <errno.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

namespace mongo {

    MemoryMappedFile::MemoryMappedFile() {
        fd = 0;
        maphandle = 0;
        view = 0;
        len = 0;
        created();
    }

    void MemoryMappedFile::close() {
        if ( view )
            munmap(view, len);
        view = 0;

        if ( fd )
            ::close(fd);
        fd = 0;
    }

#ifndef O_NOATIME
#define O_NOATIME 0
#endif

    void* MemoryMappedFile::map(const char *filename, int length) {
        updateLength( filename, length );
        len = length;

        fd = open(filename, O_CREAT | O_RDWR | O_NOATIME, S_IRUSR | S_IWUSR);
        if ( fd <= 0 ) {
            out() << "couldn't open " << filename << ' ' << errno << endl;
            return 0;
        }

        /* make sure the file is the full desired length */
        off_t filelen = lseek(fd, 0, SEEK_END);
        if ( filelen < length ) {
            //        log() << "map: file length=" << (unsigned) filelen << " want:"
            //        << length
            //        << endl;
            if ( filelen != 0 ) {
                problem() << "failure mapping new file " << filename << " length:" << length << endl;
                return 0;
            }
            // Check for end of disk.
            lseek(fd, length - 1, SEEK_SET);
            write(fd, "", 1);
            lseek(fd, 0, SEEK_SET);
            Nullstream &l = log();
            l << "new datafile " << filename << " filling with zeroes...";
            l.flush();
            Timer t;
            int z = 8192;
            char buf[z];
            memset(buf, 0, z);
            int left = length;
            while ( 1 ) {
                if ( left <= z ) {
                    write(fd, buf, left);
                    break;
                }
                write(fd, buf, z);
                left -= z;
            }
            l << "done " << ((double)t.millis())/1000.0 << " secs" << endl;
        }

        view = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
        if ( view == MAP_FAILED ) {
            out() << "  mmap() failed for " << filename << " len:" << length << " errno:" << errno << endl;
            return 0;
        }
        return view;
    }

    void MemoryMappedFile::flush(bool sync) {
        if ( msync(view, len, sync ? MS_SYNC : MS_ASYNC) )
            problem() << "msync error " << errno << endl;
    }
    

} // namespace mongo