file.c

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/*
 *  file.c
 *
 *  file system operations
 *
 *  Copyright (c) 2010-2013, PostgreSQL Global Development Group
 *  contrib/pg_upgrade/file.c
 */

#include "postgres_fe.h"

#include "pg_upgrade.h"

#include <fcntl.h>



#ifndef WIN32
static int  copy_file(const char *fromfile, const char *tofile, bool force);
#else
static int  win32_pghardlink(const char *src, const char *dst);
#endif


/*
 * copyAndUpdateFile()
 *
 *  Copies a relation file from src to dst.  If pageConverter is non-NULL, this function
 *  uses that pageConverter to do a page-by-page conversion.
 */
const char *
copyAndUpdateFile(pageCnvCtx *pageConverter,
                  const char *src, const char *dst, bool force)
{
    if (pageConverter == NULL)
    {
        if (pg_copy_file(src, dst, force) == -1)
            return getErrorText(errno);
        else
            return NULL;
    }
    else
    {
        /*
         * We have a pageConverter object - that implies that the
         * PageLayoutVersion differs between the two clusters so we have to
         * perform a page-by-page conversion.
         *
         * If the pageConverter can convert the entire file at once, invoke
         * that plugin function, otherwise, read each page in the relation
         * file and call the convertPage plugin function.
         */

#ifdef PAGE_CONVERSION
        if (pageConverter->convertFile)
            return pageConverter->convertFile(pageConverter->pluginData,
                                              dst, src);
        else
#endif
        {
            int         src_fd;
            int         dstfd;
            char        buf[BLCKSZ];
            ssize_t     bytesRead;
            const char *msg = NULL;

            if ((src_fd = open(src, O_RDONLY, 0)) < 0)
                return "could not open source file";

            if ((dstfd = open(dst, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR)) < 0)
            {
                close(src_fd);
                return "could not create destination file";
            }

            while ((bytesRead = read(src_fd, buf, BLCKSZ)) == BLCKSZ)
            {
#ifdef PAGE_CONVERSION
                if ((msg = pageConverter->convertPage(pageConverter->pluginData, buf, buf)) != NULL)
                    break;
#endif
                if (write(dstfd, buf, BLCKSZ) != BLCKSZ)
                {
                    msg = "could not write new page to destination";
                    break;
                }
            }

            close(src_fd);
            close(dstfd);

            if (msg)
                return msg;
            else if (bytesRead != 0)
                return "found partial page in source file";
            else
                return NULL;
        }
    }
}


/*
 * linkAndUpdateFile()
 *
 * Creates a hard link between the given relation files. We use
 * this function to perform a true in-place update. If the on-disk
 * format of the new cluster is bit-for-bit compatible with the on-disk
 * format of the old cluster, we can simply link each relation
 * instead of copying the data from the old cluster to the new cluster.
 */
const char *
linkAndUpdateFile(pageCnvCtx *pageConverter,
                  const char *src, const char *dst)
{
    if (pageConverter != NULL)
        return "Cannot in-place update this cluster, page-by-page conversion is required";

    if (pg_link_file(src, dst) == -1)
        return getErrorText(errno);
    else
        return NULL;
}


#ifndef WIN32
static int
copy_file(const char *srcfile, const char *dstfile, bool force)
{

#define COPY_BUF_SIZE (50 * BLCKSZ)

    int         src_fd;
    int         dest_fd;
    char       *buffer;
    int         ret = 0;
    int         save_errno = 0;

    if ((srcfile == NULL) || (dstfile == NULL))
        return -1;

    if ((src_fd = open(srcfile, O_RDONLY, 0)) < 0)
        return -1;

    if ((dest_fd = open(dstfile, O_RDWR | O_CREAT | (force ? 0 : O_EXCL), S_IRUSR | S_IWUSR)) < 0)
    {
        if (src_fd != 0)
            close(src_fd);

        return -1;
    }

    buffer = (char *) pg_malloc(COPY_BUF_SIZE);

    /* perform data copying i.e read src source, write to destination */
    while (true)
    {
        ssize_t     nbytes = read(src_fd, buffer, COPY_BUF_SIZE);

        if (nbytes < 0)
        {
            save_errno = errno;
            ret = -1;
            break;
        }

        if (nbytes == 0)
            break;

        errno = 0;

        if (write(dest_fd, buffer, nbytes) != nbytes)
        {
            save_errno = errno;
            ret = -1;
            break;
        }
    }

    pg_free(buffer);

    if (src_fd != 0)
        close(src_fd);

    if (dest_fd != 0)
        close(dest_fd);

    if (save_errno != 0)
        errno = save_errno;

    return ret;
}
#endif


void
check_hard_link(void)
{
    char        existing_file[MAXPGPATH];
    char        new_link_file[MAXPGPATH];

    snprintf(existing_file, sizeof(existing_file), "%s/PG_VERSION", old_cluster.pgdata);
    snprintf(new_link_file, sizeof(new_link_file), "%s/PG_VERSION.linktest", new_cluster.pgdata);
    unlink(new_link_file);      /* might fail */

    if (pg_link_file(existing_file, new_link_file) == -1)
    {
        pg_log(PG_FATAL,
               "Could not create hard link between old and new data directories: %s\n"
               "In link mode the old and new data directories must be on the same file system volume.\n",
               getErrorText(errno));
    }
    unlink(new_link_file);
}

#ifdef WIN32
static int
win32_pghardlink(const char *src, const char *dst)
{
    /*
     * CreateHardLinkA returns zero for failure
     * http://msdn.microsoft.com/en-us/library/aa363860(VS.85).aspx
     */
    if (CreateHardLinkA(dst, src, NULL) == 0)
        return -1;
    else
        return 0;
}
#endif


/* fopen() file with no group/other permissions */
FILE *
fopen_priv(const char *path, const char *mode)
{
    mode_t      old_umask = umask(S_IRWXG | S_IRWXO);
    FILE       *fp;

    fp = fopen(path, mode);
    umask(old_umask);

    return fp;
}