controldata_utils.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * controldata_utils.c
 *      Common code for control data file output.
 *
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/common/controldata_utils.c
 *
 *-------------------------------------------------------------------------
 */

#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif

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

#include "access/xlog_internal.h"
#include "catalog/pg_control.h"
#include "common/controldata_utils.h"
#include "common/file_perm.h"
#ifdef FRONTEND
#include "common/logging.h"
#endif
#include "port/pg_crc32c.h"

#ifndef FRONTEND
#include "pgstat.h"
#include "storage/fd.h"
#endif

/*
 * get_controlfile()
 *
 * Get controlfile values.  The result is returned as a palloc'd copy of the
 * control file data.
 *
 * crc_ok_p can be used by the caller to see whether the CRC of the control
 * file data is correct.
 */
ControlFileData *
get_controlfile(const char *DataDir, bool *crc_ok_p)
{
    ControlFileData *ControlFile;
    int         fd;
    char        ControlFilePath[MAXPGPATH];
    pg_crc32c   crc;
    int         r;

    AssertArg(crc_ok_p);

    ControlFile = palloc(sizeof(ControlFileData));
    snprintf(ControlFilePath, MAXPGPATH, "%s/global/pg_control", DataDir);

#ifndef FRONTEND
    if ((fd = OpenTransientFile(ControlFilePath, O_RDONLY | PG_BINARY)) == -1)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\" for reading: %m",
                        ControlFilePath)));
#else
    if ((fd = open(ControlFilePath, O_RDONLY | PG_BINARY, 0)) == -1)
    {
        pg_log_fatal("could not open file \"%s\" for reading: %m",
                     ControlFilePath);
        exit(EXIT_FAILURE);
    }
#endif

    r = read(fd, ControlFile, sizeof(ControlFileData));
    if (r != sizeof(ControlFileData))
    {
        if (r < 0)
#ifndef FRONTEND
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not read file \"%s\": %m", ControlFilePath)));
#else
        {
            pg_log_fatal("could not read file \"%s\": %m", ControlFilePath);
            exit(EXIT_FAILURE);
        }
#endif
        else
#ifndef FRONTEND
            ereport(ERROR,
                    (errcode(ERRCODE_DATA_CORRUPTED),
                     errmsg("could not read file \"%s\": read %d of %zu",
                            ControlFilePath, r, sizeof(ControlFileData))));
#else
        {
            pg_log_fatal("could not read file \"%s\": read %d of %zu",
                         ControlFilePath, r, sizeof(ControlFileData));
            exit(EXIT_FAILURE);
        }
#endif
    }

#ifndef FRONTEND
    if (CloseTransientFile(fd) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m",
                        ControlFilePath)));
#else
    if (close(fd) != 0)
    {
        pg_log_fatal("could not close file \"%s\": %m", ControlFilePath);
        exit(EXIT_FAILURE);
    }
#endif

    /* Check the CRC. */
    INIT_CRC32C(crc);
    COMP_CRC32C(crc,
                (char *) ControlFile,
                offsetof(ControlFileData, crc));
    FIN_CRC32C(crc);

    *crc_ok_p = EQ_CRC32C(crc, ControlFile->crc);

    /* Make sure the control file is valid byte order. */
    if (ControlFile->pg_control_version % 65536 == 0 &&
        ControlFile->pg_control_version / 65536 != 0)
#ifndef FRONTEND
        elog(ERROR, _("byte ordering mismatch"));
#else
        pg_log_warning("possible byte ordering mismatch\n"
                       "The byte ordering used to store the pg_control file might not match the one\n"
                       "used by this program.  In that case the results below would be incorrect, and\n"
                       "the PostgreSQL installation would be incompatible with this data directory.");
#endif

    return ControlFile;
}

/*
 * update_controlfile()
 *
 * Update controlfile values with the contents given by caller.  The
 * contents to write are included in "ControlFile". "do_sync" can be
 * optionally used to flush the updated control file.  Note that it is up
 * to the caller to properly lock ControlFileLock when calling this
 * routine in the backend.
 */
void
update_controlfile(const char *DataDir,
                   ControlFileData *ControlFile, bool do_sync)
{
    int         fd;
    char        buffer[PG_CONTROL_FILE_SIZE];
    char        ControlFilePath[MAXPGPATH];

    /*
     * Apply the same static assertions as in backend's WriteControlFile().
     */
    StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE,
                     "pg_control is too large for atomic disk writes");
    StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
                     "sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");

    /* Recalculate CRC of control file */
    INIT_CRC32C(ControlFile->crc);
    COMP_CRC32C(ControlFile->crc,
                (char *) ControlFile,
                offsetof(ControlFileData, crc));
    FIN_CRC32C(ControlFile->crc);

    /*
     * Write out PG_CONTROL_FILE_SIZE bytes into pg_control by zero-padding
     * the excess over sizeof(ControlFileData), to avoid premature EOF related
     * errors when reading it.
     */
    memset(buffer, 0, PG_CONTROL_FILE_SIZE);
    memcpy(buffer, ControlFile, sizeof(ControlFileData));

    snprintf(ControlFilePath, sizeof(ControlFilePath), "%s/%s", DataDir, XLOG_CONTROL_FILE);

#ifndef FRONTEND

    /*
     * All errors issue a PANIC, so no need to use OpenTransientFile() and to
     * worry about file descriptor leaks.
     */
    if ((fd = BasicOpenFile(ControlFilePath, O_RDWR | PG_BINARY)) < 0)
        ereport(PANIC,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m",
                        ControlFilePath)));
#else
    if ((fd = open(ControlFilePath, O_WRONLY | PG_BINARY,
                   pg_file_create_mode)) == -1)
    {
        pg_log_fatal("could not open file \"%s\": %m", ControlFilePath);
        exit(EXIT_FAILURE);
    }
#endif

    errno = 0;
#ifndef FRONTEND
    pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_WRITE_UPDATE);
#endif
    if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE)
    {
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;

#ifndef FRONTEND
        ereport(PANIC,
                (errcode_for_file_access(),
                 errmsg("could not write file \"%s\": %m",
                        ControlFilePath)));
#else
        pg_log_fatal("could not write file \"%s\": %m", ControlFilePath);
        exit(EXIT_FAILURE);
#endif
    }
#ifndef FRONTEND
    pgstat_report_wait_end();
#endif

    if (do_sync)
    {
#ifndef FRONTEND
        pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_SYNC_UPDATE);
        if (pg_fsync(fd) != 0)
            ereport(PANIC,
                    (errcode_for_file_access(),
                     errmsg("could not fsync file \"%s\": %m",
                            ControlFilePath)));
        pgstat_report_wait_end();
#else
        if (fsync(fd) != 0)
        {
            pg_log_fatal("could not fsync file \"%s\": %m", ControlFilePath);
            exit(EXIT_FAILURE);
        }
#endif
    }

    if (close(fd) != 0)
    {
#ifndef FRONTEND
        ereport(PANIC,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m",
                        ControlFilePath)));
#else
        pg_log_fatal("could not close file \"%s\": %m", ControlFilePath);
        exit(EXIT_FAILURE);
#endif
    }
}