file.c

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/*
 *  file.c
 *
 *  file system operations
 *
 *  Copyright (c) 2010-2018, PostgreSQL Global Development Group
 *  src/bin/pg_upgrade/file.c
 */

#include "postgres_fe.h"

#include "access/visibilitymap.h"
#include "common/file_perm.h"
#include "pg_upgrade.h"
#include "storage/bufpage.h"
#include "storage/checksum.h"
#include "storage/checksum_impl.h"

#include <sys/stat.h>
#include <fcntl.h>


#ifdef WIN32
static int  win32_pghardlink(const char *src, const char *dst);
#endif


/*
 * copyFile()
 *
 * Copies a relation file from src to dst.
 * schemaName/relName are relation's SQL name (used for error messages only).
 */
void
copyFile(const char *src, const char *dst,
         const char *schemaName, const char *relName)
{
#ifndef WIN32
    int         src_fd;
    int         dest_fd;
    char       *buffer;

    if ((src_fd = open(src, O_RDONLY | PG_BINARY, 0)) < 0)
        pg_fatal("error while copying relation \"%s.%s\": could not open file \"%s\": %s\n",
                 schemaName, relName, src, strerror(errno));

    if ((dest_fd = open(dst, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                        pg_file_create_mode)) < 0)
        pg_fatal("error while copying relation \"%s.%s\": could not create file \"%s\": %s\n",
                 schemaName, relName, dst, strerror(errno));

    /* copy in fairly large chunks for best efficiency */
#define COPY_BUF_SIZE (50 * BLCKSZ)

    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)
            pg_fatal("error while copying relation \"%s.%s\": could not read file \"%s\": %s\n",
                     schemaName, relName, src, strerror(errno));

        if (nbytes == 0)
            break;

        errno = 0;
        if (write(dest_fd, buffer, nbytes) != nbytes)
        {
            /* if write didn't set errno, assume problem is no disk space */
            if (errno == 0)
                errno = ENOSPC;
            pg_fatal("error while copying relation \"%s.%s\": could not write file \"%s\": %s\n",
                     schemaName, relName, dst, strerror(errno));
        }
    }

    pg_free(buffer);
    close(src_fd);
    close(dest_fd);

#else                           /* WIN32 */

    if (CopyFile(src, dst, true) == 0)
    {
        _dosmaperr(GetLastError());
        pg_fatal("error while copying relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
                 schemaName, relName, src, dst, strerror(errno));
    }

#endif                          /* WIN32 */
}


/*
 * linkFile()
 *
 * Hard-links a relation file from src to dst.
 * schemaName/relName are relation's SQL name (used for error messages only).
 */
void
linkFile(const char *src, const char *dst,
         const char *schemaName, const char *relName)
{
    if (pg_link_file(src, dst) < 0)
        pg_fatal("error while creating link for relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
                 schemaName, relName, src, dst, strerror(errno));
}


/*
 * rewriteVisibilityMap()
 *
 * Transform a visibility map file, copying from src to dst.
 * schemaName/relName are relation's SQL name (used for error messages only).
 *
 * In versions of PostgreSQL prior to catversion 201603011, PostgreSQL's
 * visibility map included one bit per heap page; it now includes two.
 * When upgrading a cluster from before that time to a current PostgreSQL
 * version, we could refuse to copy visibility maps from the old cluster
 * to the new cluster; the next VACUUM would recreate them, but at the
 * price of scanning the entire table.  So, instead, we rewrite the old
 * visibility maps in the new format.  That way, the all-visible bits
 * remain set for the pages for which they were set previously.  The
 * all-frozen bits are never set by this conversion; we leave that to VACUUM.
 */
void
rewriteVisibilityMap(const char *fromfile, const char *tofile,
                     const char *schemaName, const char *relName)
{
    int         src_fd;
    int         dst_fd;
    char       *buffer;
    char       *new_vmbuf;
    ssize_t     totalBytesRead = 0;
    ssize_t     src_filesize;
    int         rewriteVmBytesPerPage;
    BlockNumber new_blkno = 0;
    struct stat statbuf;

    /* Compute number of old-format bytes per new page */
    rewriteVmBytesPerPage = (BLCKSZ - SizeOfPageHeaderData) / 2;

    if ((src_fd = open(fromfile, O_RDONLY | PG_BINARY, 0)) < 0)
        pg_fatal("error while copying relation \"%s.%s\": could not open file \"%s\": %s\n",
                 schemaName, relName, fromfile, strerror(errno));

    if (fstat(src_fd, &statbuf) != 0)
        pg_fatal("error while copying relation \"%s.%s\": could not stat file \"%s\": %s\n",
                 schemaName, relName, fromfile, strerror(errno));

    if ((dst_fd = open(tofile, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                       pg_file_create_mode)) < 0)
        pg_fatal("error while copying relation \"%s.%s\": could not create file \"%s\": %s\n",
                 schemaName, relName, tofile, strerror(errno));

    /* Save old file size */
    src_filesize = statbuf.st_size;

    /*
     * Malloc the work buffers, rather than making them local arrays, to
     * ensure adequate alignment.
     */
    buffer = (char *) pg_malloc(BLCKSZ);
    new_vmbuf = (char *) pg_malloc(BLCKSZ);

    /*
     * Turn each visibility map page into 2 pages one by one. Each new page
     * has the same page header as the old one.  If the last section of the
     * last page is empty, we skip it, mostly to avoid turning one-page
     * visibility maps for small relations into two pages needlessly.
     */
    while (totalBytesRead < src_filesize)
    {
        ssize_t     bytesRead;
        char       *old_cur;
        char       *old_break;
        char       *old_blkend;
        PageHeaderData pageheader;
        bool        old_lastblk;

        if ((bytesRead = read(src_fd, buffer, BLCKSZ)) != BLCKSZ)
        {
            if (bytesRead < 0)
                pg_fatal("error while copying relation \"%s.%s\": could not read file \"%s\": %s\n",
                         schemaName, relName, fromfile, strerror(errno));
            else
                pg_fatal("error while copying relation \"%s.%s\": partial page found in file \"%s\"\n",
                         schemaName, relName, fromfile);
        }

        totalBytesRead += BLCKSZ;
        old_lastblk = (totalBytesRead == src_filesize);

        /* Save the page header data */
        memcpy(&pageheader, buffer, SizeOfPageHeaderData);

        /*
         * These old_* variables point to old visibility map page. old_cur
         * points to current position on old page. old_blkend points to end of
         * old block.  old_break is the end+1 position on the old page for the
         * data that will be transferred to the current new page.
         */
        old_cur = buffer + SizeOfPageHeaderData;
        old_blkend = buffer + bytesRead;
        old_break = old_cur + rewriteVmBytesPerPage;

        while (old_break <= old_blkend)
        {
            char       *new_cur;
            bool        empty = true;
            bool        old_lastpart;

            /* First, copy old page header to new page */
            memcpy(new_vmbuf, &pageheader, SizeOfPageHeaderData);

            /* Rewriting the last part of the last old page? */
            old_lastpart = old_lastblk && (old_break == old_blkend);

            new_cur = new_vmbuf + SizeOfPageHeaderData;

            /* Process old page bytes one by one, and turn it into new page. */
            while (old_cur < old_break)
            {
                uint8       byte = *(uint8 *) old_cur;
                uint16      new_vmbits = 0;
                int         i;

                /* Generate new format bits while keeping old information */
                for (i = 0; i < BITS_PER_BYTE; i++)
                {
                    if (byte & (1 << i))
                    {
                        empty = false;
                        new_vmbits |=
                            VISIBILITYMAP_ALL_VISIBLE << (BITS_PER_HEAPBLOCK * i);
                    }
                }

                /* Copy new visibility map bytes to new-format page */
                new_cur[0] = (char) (new_vmbits & 0xFF);
                new_cur[1] = (char) (new_vmbits >> 8);

                old_cur++;
                new_cur += BITS_PER_HEAPBLOCK;
            }

            /* If the last part of the last page is empty, skip writing it */
            if (old_lastpart && empty)
                break;

            /* Set new checksum for visibility map page, if enabled */
            if (new_cluster.controldata.data_checksum_version != 0)
                ((PageHeader) new_vmbuf)->pd_checksum =
                    pg_checksum_page(new_vmbuf, new_blkno);

            errno = 0;
            if (write(dst_fd, new_vmbuf, BLCKSZ) != BLCKSZ)
            {
                /* if write didn't set errno, assume problem is no disk space */
                if (errno == 0)
                    errno = ENOSPC;
                pg_fatal("error while copying relation \"%s.%s\": could not write file \"%s\": %s\n",
                         schemaName, relName, tofile, strerror(errno));
            }

            /* Advance for next new page */
            old_break += rewriteVmBytesPerPage;
            new_blkno++;
        }
    }

    /* Clean up */
    pg_free(buffer);
    pg_free(new_vmbuf);
    close(dst_fd);
    close(src_fd);
}

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) < 0)
        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.\n",
                 strerror(errno));

    unlink(new_link_file);
}

#ifdef WIN32
/* implementation of pg_link_file() on Windows */
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)
    {
        _dosmaperr(GetLastError());
        return -1;
    }
    else
        return 0;
}
#endif