Update copyright for 2022

[pgsql.git] / src / backend / replication / basebackup.c

/*-------------------------------------------------------------------------
 *
 * basebackup.c
 *        code for taking a base backup and streaming it to a standby
 *
 * Portions Copyright (c) 2010-2022, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        src/backend/replication/basebackup.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

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

#include "access/xlog_internal.h"       /* for pg_start/stop_backup */
#include "common/file_perm.h"
#include "commands/defrem.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "nodes/pg_list.h"
#include "pgstat.h"
#include "pgtar.h"
#include "port.h"
#include "postmaster/syslogger.h"
#include "replication/basebackup.h"
#include "replication/basebackup_sink.h"
#include "replication/backup_manifest.h"
#include "replication/walsender.h"
#include "replication/walsender_private.h"
#include "storage/bufpage.h"
#include "storage/checksum.h"
#include "storage/dsm_impl.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/reinit.h"
#include "utils/builtins.h"
#include "utils/ps_status.h"
#include "utils/relcache.h"
#include "utils/resowner.h"
#include "utils/timestamp.h"

/*
 * How much data do we want to send in one CopyData message? Note that
 * this may also result in reading the underlying files in chunks of this
 * size.
 *
 * NB: The buffer size is required to be a multiple of the system block
 * size, so use that value instead if it's bigger than our preference.
 */
#define SINK_BUFFER_LENGTH                      Max(32768, BLCKSZ)

typedef struct
{
        const char *label;
        bool            progress;
        bool            fastcheckpoint;
        bool            nowait;
        bool            includewal;
        uint32          maxrate;
        bool            sendtblspcmapfile;
        backup_manifest_option manifest;
        pg_checksum_type manifest_checksum_type;
} basebackup_options;

static int64 sendTablespace(bbsink *sink, char *path, char *oid, bool sizeonly,
                                                        struct backup_manifest_info *manifest);
static int64 sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
                                         List *tablespaces, bool sendtblspclinks,
                                         backup_manifest_info *manifest, const char *spcoid);
static bool sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
                                         struct stat *statbuf, bool missing_ok, Oid dboid,
                                         backup_manifest_info *manifest, const char *spcoid);
static void sendFileWithContent(bbsink *sink, const char *filename,
                                                                const char *content,
                                                                backup_manifest_info *manifest);
static int64 _tarWriteHeader(bbsink *sink, const char *filename,
                                                         const char *linktarget, struct stat *statbuf,
                                                         bool sizeonly);
static void _tarWritePadding(bbsink *sink, int len);
static void convert_link_to_directory(const char *pathbuf, struct stat *statbuf);
static void perform_base_backup(basebackup_options *opt, bbsink *sink);
static void parse_basebackup_options(List *options, basebackup_options *opt);
static int      compareWalFileNames(const ListCell *a, const ListCell *b);
static bool is_checksummed_file(const char *fullpath, const char *filename);
static int      basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
                                                                 const char *filename, bool partial_read_ok);

/* Was the backup currently in-progress initiated in recovery mode? */
static bool backup_started_in_recovery = false;

/* Relative path of temporary statistics directory */
static char *statrelpath = NULL;

/* Total number of checksum failures during base backup. */
static long long int total_checksum_failures;

/* Do not verify checksums. */
static bool noverify_checksums = false;

/*
 * Definition of one element part of an exclusion list, used for paths part
 * of checksum validation or base backups.  "name" is the name of the file
 * or path to check for exclusion.  If "match_prefix" is true, any items
 * matching the name as prefix are excluded.
 */
struct exclude_list_item
{
        const char *name;
        bool            match_prefix;
};

/*
 * The contents of these directories are removed or recreated during server
 * start so they are not included in backups.  The directories themselves are
 * kept and included as empty to preserve access permissions.
 *
 * Note: this list should be kept in sync with the filter lists in pg_rewind's
 * filemap.c.
 */
static const char *const excludeDirContents[] =
{
        /*
         * Skip temporary statistics files. PG_STAT_TMP_DIR must be skipped even
         * when stats_temp_directory is set because PGSS_TEXT_FILE is always
         * created there.
         */
        PG_STAT_TMP_DIR,

        /*
         * It is generally not useful to backup the contents of this directory
         * even if the intention is to restore to another primary. See backup.sgml
         * for a more detailed description.
         */
        "pg_replslot",

        /* Contents removed on startup, see dsm_cleanup_for_mmap(). */
        PG_DYNSHMEM_DIR,

        /* Contents removed on startup, see AsyncShmemInit(). */
        "pg_notify",

        /*
         * Old contents are loaded for possible debugging but are not required for
         * normal operation, see SerialInit().
         */
        "pg_serial",

        /* Contents removed on startup, see DeleteAllExportedSnapshotFiles(). */
        "pg_snapshots",

        /* Contents zeroed on startup, see StartupSUBTRANS(). */
        "pg_subtrans",

        /* end of list */
        NULL
};

/*
 * List of files excluded from backups.
 */
static const struct exclude_list_item excludeFiles[] =
{
        /* Skip auto conf temporary file. */
        {PG_AUTOCONF_FILENAME ".tmp", false},

        /* Skip current log file temporary file */
        {LOG_METAINFO_DATAFILE_TMP, false},

        /*
         * Skip relation cache because it is rebuilt on startup.  This includes
         * temporary files.
         */
        {RELCACHE_INIT_FILENAME, true},

        /*
         * If there's a backup_label or tablespace_map file, it belongs to a
         * backup started by the user with pg_start_backup().  It is *not* correct
         * for this backup.  Our backup_label/tablespace_map is injected into the
         * tar separately.
         */
        {BACKUP_LABEL_FILE, false},
        {TABLESPACE_MAP, false},

        /*
         * If there's a backup_manifest, it belongs to a backup that was used to
         * start this server. It is *not* correct for this backup. Our
         * backup_manifest is injected into the backup separately if users want
         * it.
         */
        {"backup_manifest", false},

        {"postmaster.pid", false},
        {"postmaster.opts", false},

        /* end of list */
        {NULL, false}
};

/*
 * List of files excluded from checksum validation.
 *
 * Note: this list should be kept in sync with what pg_checksums.c
 * includes.
 */
static const struct exclude_list_item noChecksumFiles[] = {
        {"pg_control", false},
        {"pg_filenode.map", false},
        {"pg_internal.init", true},
        {"PG_VERSION", false},
#ifdef EXEC_BACKEND
        {"config_exec_params", true},
#endif
        {NULL, false}
};

/*
 * Actually do a base backup for the specified tablespaces.
 *
 * This is split out mainly to avoid complaints about "variable might be
 * clobbered by longjmp" from stupider versions of gcc.
 */
static void
perform_base_backup(basebackup_options *opt, bbsink *sink)
{
        bbsink_state state;
        XLogRecPtr      endptr;
        TimeLineID      endtli;
        StringInfo      labelfile;
        StringInfo      tblspc_map_file;
        backup_manifest_info manifest;
        int                     datadirpathlen;

        /* Initial backup state, insofar as we know it now. */
        state.tablespaces = NIL;
        state.tablespace_num = 0;
        state.bytes_done = 0;
        state.bytes_total = 0;
        state.bytes_total_is_valid = false;

        /* we're going to use a BufFile, so we need a ResourceOwner */
        Assert(CurrentResourceOwner == NULL);
        CurrentResourceOwner = ResourceOwnerCreate(NULL, "base backup");

        datadirpathlen = strlen(DataDir);

        backup_started_in_recovery = RecoveryInProgress();

        labelfile = makeStringInfo();
        tblspc_map_file = makeStringInfo();
        InitializeBackupManifest(&manifest, opt->manifest,
                                                         opt->manifest_checksum_type);

        total_checksum_failures = 0;

        basebackup_progress_wait_checkpoint();
        state.startptr = do_pg_start_backup(opt->label, opt->fastcheckpoint,
                                                                                &state.starttli,
                                                                                labelfile, &state.tablespaces,
                                                                                tblspc_map_file);

        /*
         * Once do_pg_start_backup has been called, ensure that any failure causes
         * us to abort the backup so we don't "leak" a backup counter. For this
         * reason, *all* functionality between do_pg_start_backup() and the end of
         * do_pg_stop_backup() should be inside the error cleanup block!
         */

        PG_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
        {
                ListCell   *lc;
                tablespaceinfo *ti;

                /*
                 * Calculate the relative path of temporary statistics directory in
                 * order to skip the files which are located in that directory later.
                 */
                if (is_absolute_path(pgstat_stat_directory) &&
                        strncmp(pgstat_stat_directory, DataDir, datadirpathlen) == 0)
                        statrelpath = psprintf("./%s", pgstat_stat_directory + datadirpathlen + 1);
                else if (strncmp(pgstat_stat_directory, "./", 2) != 0)
                        statrelpath = psprintf("./%s", pgstat_stat_directory);
                else
                        statrelpath = pgstat_stat_directory;

                /* Add a node for the base directory at the end */
                ti = palloc0(sizeof(tablespaceinfo));
                ti->size = -1;
                state.tablespaces = lappend(state.tablespaces, ti);

                /*
                 * Calculate the total backup size by summing up the size of each
                 * tablespace
                 */
                if (opt->progress)
                {
                        basebackup_progress_estimate_backup_size();

                        foreach(lc, state.tablespaces)
                        {
                                tablespaceinfo *tmp = (tablespaceinfo *) lfirst(lc);

                                if (tmp->path == NULL)
                                        tmp->size = sendDir(sink, ".", 1, true, state.tablespaces,
                                                                                true, NULL, NULL);
                                else
                                        tmp->size = sendTablespace(sink, tmp->path, tmp->oid, true,
                                                                                           NULL);
                                state.bytes_total += tmp->size;
                        }
                        state.bytes_total_is_valid = true;
                }

                /* notify basebackup sink about start of backup */
                bbsink_begin_backup(sink, &state, SINK_BUFFER_LENGTH);

                /* Send off our tablespaces one by one */
                foreach(lc, state.tablespaces)
                {
                        tablespaceinfo *ti = (tablespaceinfo *) lfirst(lc);

                        if (ti->path == NULL)
                        {
                                struct stat statbuf;
                                bool            sendtblspclinks = true;

                                bbsink_begin_archive(sink, "base.tar");

                                /* In the main tar, include the backup_label first... */
                                sendFileWithContent(sink, BACKUP_LABEL_FILE, labelfile->data,
                                                                        &manifest);

                                /* Then the tablespace_map file, if required... */
                                if (opt->sendtblspcmapfile)
                                {
                                        sendFileWithContent(sink, TABLESPACE_MAP, tblspc_map_file->data,
                                                                                &manifest);
                                        sendtblspclinks = false;
                                }

                                /* Then the bulk of the files... */
                                sendDir(sink, ".", 1, false, state.tablespaces,
                                                sendtblspclinks, &manifest, NULL);

                                /* ... and pg_control after everything else. */
                                if (lstat(XLOG_CONTROL_FILE, &statbuf) != 0)
                                        ereport(ERROR,
                                                        (errcode_for_file_access(),
                                                         errmsg("could not stat file \"%s\": %m",
                                                                        XLOG_CONTROL_FILE)));
                                sendFile(sink, XLOG_CONTROL_FILE, XLOG_CONTROL_FILE, &statbuf,
                                                 false, InvalidOid, &manifest, NULL);
                        }
                        else
                        {
                                char       *archive_name = psprintf("%s.tar", ti->oid);

                                bbsink_begin_archive(sink, archive_name);

                                sendTablespace(sink, ti->path, ti->oid, false, &manifest);
                        }

                        /*
                         * If we're including WAL, and this is the main data directory we
                         * don't treat this as the end of the tablespace. Instead, we will
                         * include the xlog files below and stop afterwards. This is safe
                         * since the main data directory is always sent *last*.
                         */
                        if (opt->includewal && ti->path == NULL)
                        {
                                Assert(lnext(state.tablespaces, lc) == NULL);
                        }
                        else
                        {
                                /* Properly terminate the tarfile. */
                                StaticAssertStmt(2 * TAR_BLOCK_SIZE <= BLCKSZ,
                                                                 "BLCKSZ too small for 2 tar blocks");
                                memset(sink->bbs_buffer, 0, 2 * TAR_BLOCK_SIZE);
                                bbsink_archive_contents(sink, 2 * TAR_BLOCK_SIZE);

                                /* OK, that's the end of the archive. */
                                bbsink_end_archive(sink);
                        }
                }

                basebackup_progress_wait_wal_archive(&state);
                endptr = do_pg_stop_backup(labelfile->data, !opt->nowait, &endtli);
        }
        PG_END_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));


        if (opt->includewal)
        {
                /*
                 * We've left the last tar file "open", so we can now append the
                 * required WAL files to it.
                 */
                char            pathbuf[MAXPGPATH];
                XLogSegNo       segno;
                XLogSegNo       startsegno;
                XLogSegNo       endsegno;
                struct stat statbuf;
                List       *historyFileList = NIL;
                List       *walFileList = NIL;
                char            firstoff[MAXFNAMELEN];
                char            lastoff[MAXFNAMELEN];
                DIR                *dir;
                struct dirent *de;
                ListCell   *lc;
                TimeLineID      tli;

                basebackup_progress_transfer_wal();

                /*
                 * I'd rather not worry about timelines here, so scan pg_wal and
                 * include all WAL files in the range between 'startptr' and 'endptr',
                 * regardless of the timeline the file is stamped with. If there are
                 * some spurious WAL files belonging to timelines that don't belong in
                 * this server's history, they will be included too. Normally there
                 * shouldn't be such files, but if there are, there's little harm in
                 * including them.
                 */
                XLByteToSeg(state.startptr, startsegno, wal_segment_size);
                XLogFileName(firstoff, state.starttli, startsegno, wal_segment_size);
                XLByteToPrevSeg(endptr, endsegno, wal_segment_size);
                XLogFileName(lastoff, endtli, endsegno, wal_segment_size);

                dir = AllocateDir("pg_wal");
                while ((de = ReadDir(dir, "pg_wal")) != NULL)
                {
                        /* Does it look like a WAL segment, and is it in the range? */
                        if (IsXLogFileName(de->d_name) &&
                                strcmp(de->d_name + 8, firstoff + 8) >= 0 &&
                                strcmp(de->d_name + 8, lastoff + 8) <= 0)
                        {
                                walFileList = lappend(walFileList, pstrdup(de->d_name));
                        }
                        /* Does it look like a timeline history file? */
                        else if (IsTLHistoryFileName(de->d_name))
                        {
                                historyFileList = lappend(historyFileList, pstrdup(de->d_name));
                        }
                }
                FreeDir(dir);

                /*
                 * Before we go any further, check that none of the WAL segments we
                 * need were removed.
                 */
                CheckXLogRemoved(startsegno, state.starttli);

                /*
                 * Sort the WAL filenames.  We want to send the files in order from
                 * oldest to newest, to reduce the chance that a file is recycled
                 * before we get a chance to send it over.
                 */
                list_sort(walFileList, compareWalFileNames);

                /*
                 * There must be at least one xlog file in the pg_wal directory, since
                 * we are doing backup-including-xlog.
                 */
                if (walFileList == NIL)
                        ereport(ERROR,
                                        (errmsg("could not find any WAL files")));

                /*
                 * Sanity check: the first and last segment should cover startptr and
                 * endptr, with no gaps in between.
                 */
                XLogFromFileName((char *) linitial(walFileList),
                                                 &tli, &segno, wal_segment_size);
                if (segno != startsegno)
                {
                        char            startfname[MAXFNAMELEN];

                        XLogFileName(startfname, state.starttli, startsegno,
                                                 wal_segment_size);
                        ereport(ERROR,
                                        (errmsg("could not find WAL file \"%s\"", startfname)));
                }
                foreach(lc, walFileList)
                {
                        char       *walFileName = (char *) lfirst(lc);
                        XLogSegNo       currsegno = segno;
                        XLogSegNo       nextsegno = segno + 1;

                        XLogFromFileName(walFileName, &tli, &segno, wal_segment_size);
                        if (!(nextsegno == segno || currsegno == segno))
                        {
                                char            nextfname[MAXFNAMELEN];

                                XLogFileName(nextfname, tli, nextsegno, wal_segment_size);
                                ereport(ERROR,
                                                (errmsg("could not find WAL file \"%s\"", nextfname)));
                        }
                }
                if (segno != endsegno)
                {
                        char            endfname[MAXFNAMELEN];

                        XLogFileName(endfname, endtli, endsegno, wal_segment_size);
                        ereport(ERROR,
                                        (errmsg("could not find WAL file \"%s\"", endfname)));
                }

                /* Ok, we have everything we need. Send the WAL files. */
                foreach(lc, walFileList)
                {
                        char       *walFileName = (char *) lfirst(lc);
                        int                     fd;
                        size_t          cnt;
                        pgoff_t         len = 0;

                        snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", walFileName);
                        XLogFromFileName(walFileName, &tli, &segno, wal_segment_size);

                        fd = OpenTransientFile(pathbuf, O_RDONLY | PG_BINARY);
                        if (fd < 0)
                        {
                                int                     save_errno = errno;

                                /*
                                 * Most likely reason for this is that the file was already
                                 * removed by a checkpoint, so check for that to get a better
                                 * error message.
                                 */
                                CheckXLogRemoved(segno, tli);

                                errno = save_errno;
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not open file \"%s\": %m", pathbuf)));
                        }

                        if (fstat(fd, &statbuf) != 0)
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not stat file \"%s\": %m",
                                                                pathbuf)));
                        if (statbuf.st_size != wal_segment_size)
                        {
                                CheckXLogRemoved(segno, tli);
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("unexpected WAL file size \"%s\"", walFileName)));
                        }

                        /* send the WAL file itself */
                        _tarWriteHeader(sink, pathbuf, NULL, &statbuf, false);

                        while ((cnt = basebackup_read_file(fd, sink->bbs_buffer,
                                                                                           Min(sink->bbs_buffer_length,
                                                                                                   wal_segment_size - len),
                                                                                           len, pathbuf, true)) > 0)
                        {
                                CheckXLogRemoved(segno, tli);
                                bbsink_archive_contents(sink, cnt);

                                len += cnt;

                                if (len == wal_segment_size)
                                        break;
                        }

                        if (len != wal_segment_size)
                        {
                                CheckXLogRemoved(segno, tli);
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("unexpected WAL file size \"%s\"", walFileName)));
                        }

                        /*
                         * wal_segment_size is a multiple of TAR_BLOCK_SIZE, so no need
                         * for padding.
                         */
                        Assert(wal_segment_size % TAR_BLOCK_SIZE == 0);

                        CloseTransientFile(fd);

                        /*
                         * Mark file as archived, otherwise files can get archived again
                         * after promotion of a new node. This is in line with
                         * walreceiver.c always doing an XLogArchiveForceDone() after a
                         * complete segment.
                         */
                        StatusFilePath(pathbuf, walFileName, ".done");
                        sendFileWithContent(sink, pathbuf, "", &manifest);
                }

                /*
                 * Send timeline history files too. Only the latest timeline history
                 * file is required for recovery, and even that only if there happens
                 * to be a timeline switch in the first WAL segment that contains the
                 * checkpoint record, or if we're taking a base backup from a standby
                 * server and the target timeline changes while the backup is taken.
                 * But they are small and highly useful for debugging purposes, so
                 * better include them all, always.
                 */
                foreach(lc, historyFileList)
                {
                        char       *fname = lfirst(lc);

                        snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", fname);

                        if (lstat(pathbuf, &statbuf) != 0)
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not stat file \"%s\": %m", pathbuf)));

                        sendFile(sink, pathbuf, pathbuf, &statbuf, false, InvalidOid,
                                         &manifest, NULL);

                        /* unconditionally mark file as archived */
                        StatusFilePath(pathbuf, fname, ".done");
                        sendFileWithContent(sink, pathbuf, "", &manifest);
                }

                /* Properly terminate the tar file. */
                StaticAssertStmt(2 * TAR_BLOCK_SIZE <= BLCKSZ,
                                                 "BLCKSZ too small for 2 tar blocks");
                memset(sink->bbs_buffer, 0, 2 * TAR_BLOCK_SIZE);
                bbsink_archive_contents(sink, 2 * TAR_BLOCK_SIZE);

                /* OK, that's the end of the archive. */
                bbsink_end_archive(sink);
        }

        AddWALInfoToBackupManifest(&manifest, state.startptr, state.starttli,
                                                           endptr, endtli);

        SendBackupManifest(&manifest, sink);

        bbsink_end_backup(sink, endptr, endtli);

        if (total_checksum_failures)
        {
                if (total_checksum_failures > 1)
                        ereport(WARNING,
                                        (errmsg_plural("%lld total checksum verification failure",
                                                                   "%lld total checksum verification failures",
                                                                   total_checksum_failures,
                                                                   total_checksum_failures)));

                ereport(ERROR,
                                (errcode(ERRCODE_DATA_CORRUPTED),
                                 errmsg("checksum verification failure during base backup")));
        }

        /*
         * Make sure to free the manifest before the resource owners as manifests
         * use cryptohash contexts that may depend on resource owners (like
         * OpenSSL).
         */
        FreeBackupManifest(&manifest);

        /* clean up the resource owner we created */
        WalSndResourceCleanup(true);

        basebackup_progress_done();
}

/*
 * list_sort comparison function, to compare log/seg portion of WAL segment
 * filenames, ignoring the timeline portion.
 */
static int
compareWalFileNames(const ListCell *a, const ListCell *b)
{
        char       *fna = (char *) lfirst(a);
        char       *fnb = (char *) lfirst(b);

        return strcmp(fna + 8, fnb + 8);
}

/*
 * Parse the base backup options passed down by the parser
 */
static void
parse_basebackup_options(List *options, basebackup_options *opt)
{
        ListCell   *lopt;
        bool            o_label = false;
        bool            o_progress = false;
        bool            o_checkpoint = false;
        bool            o_nowait = false;
        bool            o_wal = false;
        bool            o_maxrate = false;
        bool            o_tablespace_map = false;
        bool            o_noverify_checksums = false;
        bool            o_manifest = false;
        bool            o_manifest_checksums = false;

        MemSet(opt, 0, sizeof(*opt));
        opt->manifest = MANIFEST_OPTION_NO;
        opt->manifest_checksum_type = CHECKSUM_TYPE_CRC32C;

        foreach(lopt, options)
        {
                DefElem    *defel = (DefElem *) lfirst(lopt);

                if (strcmp(defel->defname, "label") == 0)
                {
                        if (o_label)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        opt->label = defGetString(defel);
                        o_label = true;
                }
                else if (strcmp(defel->defname, "progress") == 0)
                {
                        if (o_progress)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        opt->progress = defGetBoolean(defel);
                        o_progress = true;
                }
                else if (strcmp(defel->defname, "checkpoint") == 0)
                {
                        char       *optval = defGetString(defel);

                        if (o_checkpoint)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        if (pg_strcasecmp(optval, "fast") == 0)
                                opt->fastcheckpoint = true;
                        else if (pg_strcasecmp(optval, "spread") == 0)
                                opt->fastcheckpoint = false;
                        else
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("unrecognized checkpoint type: \"%s\"",
                                                                optval)));
                        o_checkpoint = true;
                }
                else if (strcmp(defel->defname, "wait") == 0)
                {
                        if (o_nowait)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        opt->nowait = !defGetBoolean(defel);
                        o_nowait = true;
                }
                else if (strcmp(defel->defname, "wal") == 0)
                {
                        if (o_wal)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        opt->includewal = defGetBoolean(defel);
                        o_wal = true;
                }
                else if (strcmp(defel->defname, "max_rate") == 0)
                {
                        int64           maxrate;

                        if (o_maxrate)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));

                        maxrate = defGetInt64(defel);
                        if (maxrate < MAX_RATE_LOWER || maxrate > MAX_RATE_UPPER)
                                ereport(ERROR,
                                                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                                                 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
                                                                (int) maxrate, "MAX_RATE", MAX_RATE_LOWER, MAX_RATE_UPPER)));

                        opt->maxrate = (uint32) maxrate;
                        o_maxrate = true;
                }
                else if (strcmp(defel->defname, "tablespace_map") == 0)
                {
                        if (o_tablespace_map)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        opt->sendtblspcmapfile = defGetBoolean(defel);
                        o_tablespace_map = true;
                }
                else if (strcmp(defel->defname, "verify_checksums") == 0)
                {
                        if (o_noverify_checksums)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        noverify_checksums = !defGetBoolean(defel);
                        o_noverify_checksums = true;
                }
                else if (strcmp(defel->defname, "manifest") == 0)
                {
                        char       *optval = defGetString(defel);
                        bool            manifest_bool;

                        if (o_manifest)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        if (parse_bool(optval, &manifest_bool))
                        {
                                if (manifest_bool)
                                        opt->manifest = MANIFEST_OPTION_YES;
                                else
                                        opt->manifest = MANIFEST_OPTION_NO;
                        }
                        else if (pg_strcasecmp(optval, "force-encode") == 0)
                                opt->manifest = MANIFEST_OPTION_FORCE_ENCODE;
                        else
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("unrecognized manifest option: \"%s\"",
                                                                optval)));
                        o_manifest = true;
                }
                else if (strcmp(defel->defname, "manifest_checksums") == 0)
                {
                        char       *optval = defGetString(defel);

                        if (o_manifest_checksums)
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("duplicate option \"%s\"", defel->defname)));
                        if (!pg_checksum_parse_type(optval,
                                                                                &opt->manifest_checksum_type))
                                ereport(ERROR,
                                                (errcode(ERRCODE_SYNTAX_ERROR),
                                                 errmsg("unrecognized checksum algorithm: \"%s\"",
                                                                optval)));
                        o_manifest_checksums = true;
                }
                else
                        ereport(ERROR,
                                        errcode(ERRCODE_SYNTAX_ERROR),
                                        errmsg("option \"%s\" not recognized",
                                                   defel->defname));
        }
        if (opt->label == NULL)
                opt->label = "base backup";
        if (opt->manifest == MANIFEST_OPTION_NO)
        {
                if (o_manifest_checksums)
                        ereport(ERROR,
                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                         errmsg("manifest checksums require a backup manifest")));
                opt->manifest_checksum_type = CHECKSUM_TYPE_NONE;
        }
}


/*
 * SendBaseBackup() - send a complete base backup.
 *
 * The function will put the system into backup mode like pg_start_backup()
 * does, so that the backup is consistent even though we read directly from
 * the filesystem, bypassing the buffer cache.
 */
void
SendBaseBackup(BaseBackupCmd *cmd)
{
        basebackup_options opt;
        bbsink     *sink;

        parse_basebackup_options(cmd->options, &opt);

        WalSndSetState(WALSNDSTATE_BACKUP);

        if (update_process_title)
        {
                char            activitymsg[50];

                snprintf(activitymsg, sizeof(activitymsg), "sending backup \"%s\"",
                                 opt.label);
                set_ps_display(activitymsg);
        }

        /* Create a basic basebackup sink. */
        sink = bbsink_copytblspc_new();

        /* Set up network throttling, if client requested it */
        if (opt.maxrate > 0)
                sink = bbsink_throttle_new(sink, opt.maxrate);

        /* Set up progress reporting. */
        sink = bbsink_progress_new(sink, opt.progress);

        /*
         * Perform the base backup, but make sure we clean up the bbsink even if
         * an error occurs.
         */
        PG_TRY();
        {
                perform_base_backup(&opt, sink);
        }
        PG_FINALLY();
        {
                bbsink_cleanup(sink);
        }
        PG_END_TRY();
}

/*
 * Inject a file with given name and content in the output tar stream.
 */
static void
sendFileWithContent(bbsink *sink, const char *filename, const char *content,
                                        backup_manifest_info *manifest)
{
        struct stat statbuf;
        int                     bytes_done = 0,
                                len;
        pg_checksum_context checksum_ctx;

        if (pg_checksum_init(&checksum_ctx, manifest->checksum_type) < 0)
                elog(ERROR, "could not initialize checksum of file \"%s\"",
                         filename);

        len = strlen(content);

        /*
         * Construct a stat struct for the backup_label file we're injecting in
         * the tar.
         */
        /* Windows doesn't have the concept of uid and gid */
#ifdef WIN32
        statbuf.st_uid = 0;
        statbuf.st_gid = 0;
#else
        statbuf.st_uid = geteuid();
        statbuf.st_gid = getegid();
#endif
        statbuf.st_mtime = time(NULL);
        statbuf.st_mode = pg_file_create_mode;
        statbuf.st_size = len;

        _tarWriteHeader(sink, filename, NULL, &statbuf, false);

        if (pg_checksum_update(&checksum_ctx, (uint8 *) content, len) < 0)
                elog(ERROR, "could not update checksum of file \"%s\"",
                         filename);

        while (bytes_done < len)
        {
                size_t          remaining = len - bytes_done;
                size_t          nbytes = Min(sink->bbs_buffer_length, remaining);

                memcpy(sink->bbs_buffer, content, nbytes);
                bbsink_archive_contents(sink, nbytes);
                bytes_done += nbytes;
        }

        _tarWritePadding(sink, len);

        AddFileToBackupManifest(manifest, NULL, filename, len,
                                                        (pg_time_t) statbuf.st_mtime, &checksum_ctx);
}

/*
 * Include the tablespace directory pointed to by 'path' in the output tar
 * stream.  If 'sizeonly' is true, we just calculate a total length and return
 * it, without actually sending anything.
 *
 * Only used to send auxiliary tablespaces, not PGDATA.
 */
static int64
sendTablespace(bbsink *sink, char *path, char *spcoid, bool sizeonly,
                           backup_manifest_info *manifest)
{
        int64           size;
        char            pathbuf[MAXPGPATH];
        struct stat statbuf;

        /*
         * 'path' points to the tablespace location, but we only want to include
         * the version directory in it that belongs to us.
         */
        snprintf(pathbuf, sizeof(pathbuf), "%s/%s", path,
                         TABLESPACE_VERSION_DIRECTORY);

        /*
         * Store a directory entry in the tar file so we get the permissions
         * right.
         */
        if (lstat(pathbuf, &statbuf) != 0)
        {
                if (errno != ENOENT)
                        ereport(ERROR,
                                        (errcode_for_file_access(),
                                         errmsg("could not stat file or directory \"%s\": %m",
                                                        pathbuf)));

                /* If the tablespace went away while scanning, it's no error. */
                return 0;
        }

        size = _tarWriteHeader(sink, TABLESPACE_VERSION_DIRECTORY, NULL, &statbuf,
                                                   sizeonly);

        /* Send all the files in the tablespace version directory */
        size += sendDir(sink, pathbuf, strlen(path), sizeonly, NIL, true, manifest,
                                        spcoid);

        return size;
}

/*
 * Include all files from the given directory in the output tar stream. If
 * 'sizeonly' is true, we just calculate a total length and return it, without
 * actually sending anything.
 *
 * Omit any directory in the tablespaces list, to avoid backing up
 * tablespaces twice when they were created inside PGDATA.
 *
 * If sendtblspclinks is true, we need to include symlink
 * information in the tar file. If not, we can skip that
 * as it will be sent separately in the tablespace_map file.
 */
static int64
sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
                List *tablespaces, bool sendtblspclinks, backup_manifest_info *manifest,
                const char *spcoid)
{
        DIR                *dir;
        struct dirent *de;
        char            pathbuf[MAXPGPATH * 2];
        struct stat statbuf;
        int64           size = 0;
        const char *lastDir;            /* Split last dir from parent path. */
        bool            isDbDir = false;        /* Does this directory contain relations? */

        /*
         * Determine if the current path is a database directory that can contain
         * relations.
         *
         * Start by finding the location of the delimiter between the parent path
         * and the current path.
         */
        lastDir = last_dir_separator(path);

        /* Does this path look like a database path (i.e. all digits)? */
        if (lastDir != NULL &&
                strspn(lastDir + 1, "0123456789") == strlen(lastDir + 1))
        {
                /* Part of path that contains the parent directory. */
                int                     parentPathLen = lastDir - path;

                /*
                 * Mark path as a database directory if the parent path is either
                 * $PGDATA/base or a tablespace version path.
                 */
                if (strncmp(path, "./base", parentPathLen) == 0 ||
                        (parentPathLen >= (sizeof(TABLESPACE_VERSION_DIRECTORY) - 1) &&
                         strncmp(lastDir - (sizeof(TABLESPACE_VERSION_DIRECTORY) - 1),
                                         TABLESPACE_VERSION_DIRECTORY,
                                         sizeof(TABLESPACE_VERSION_DIRECTORY) - 1) == 0))
                        isDbDir = true;
        }

        dir = AllocateDir(path);
        while ((de = ReadDir(dir, path)) != NULL)
        {
                int                     excludeIdx;
                bool            excludeFound;
                ForkNumber      relForkNum; /* Type of fork if file is a relation */
                int                     relOidChars;    /* Chars in filename that are the rel oid */

                /* Skip special stuff */
                if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
                        continue;

                /* Skip temporary files */
                if (strncmp(de->d_name,
                                        PG_TEMP_FILE_PREFIX,
                                        strlen(PG_TEMP_FILE_PREFIX)) == 0)
                        continue;

                /*
                 * Check if the postmaster has signaled us to exit, and abort with an
                 * error in that case. The error handler further up will call
                 * do_pg_abort_backup() for us. Also check that if the backup was
                 * started while still in recovery, the server wasn't promoted.
                 * do_pg_stop_backup() will check that too, but it's better to stop
                 * the backup early than continue to the end and fail there.
                 */
                CHECK_FOR_INTERRUPTS();
                if (RecoveryInProgress() != backup_started_in_recovery)
                        ereport(ERROR,
                                        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                                         errmsg("the standby was promoted during online backup"),
                                         errhint("This means that the backup being taken is corrupt "
                                                         "and should not be used. "
                                                         "Try taking another online backup.")));

                /* Scan for files that should be excluded */
                excludeFound = false;
                for (excludeIdx = 0; excludeFiles[excludeIdx].name != NULL; excludeIdx++)
                {
                        int                     cmplen = strlen(excludeFiles[excludeIdx].name);

                        if (!excludeFiles[excludeIdx].match_prefix)
                                cmplen++;
                        if (strncmp(de->d_name, excludeFiles[excludeIdx].name, cmplen) == 0)
                        {
                                elog(DEBUG1, "file \"%s\" excluded from backup", de->d_name);
                                excludeFound = true;
                                break;
                        }
                }

                if (excludeFound)
                        continue;

                /* Exclude all forks for unlogged tables except the init fork */
                if (isDbDir &&
                        parse_filename_for_nontemp_relation(de->d_name, &relOidChars,
                                                                                                &relForkNum))
                {
                        /* Never exclude init forks */
                        if (relForkNum != INIT_FORKNUM)
                        {
                                char            initForkFile[MAXPGPATH];
                                char            relOid[OIDCHARS + 1];

                                /*
                                 * If any other type of fork, check if there is an init fork
                                 * with the same OID. If so, the file can be excluded.
                                 */
                                memcpy(relOid, de->d_name, relOidChars);
                                relOid[relOidChars] = '\0';
                                snprintf(initForkFile, sizeof(initForkFile), "%s/%s_init",
                                                 path, relOid);

                                if (lstat(initForkFile, &statbuf) == 0)
                                {
                                        elog(DEBUG2,
                                                 "unlogged relation file \"%s\" excluded from backup",
                                                 de->d_name);

                                        continue;
                                }
                        }
                }

                /* Exclude temporary relations */
                if (isDbDir && looks_like_temp_rel_name(de->d_name))
                {
                        elog(DEBUG2,
                                 "temporary relation file \"%s\" excluded from backup",
                                 de->d_name);

                        continue;
                }

                snprintf(pathbuf, sizeof(pathbuf), "%s/%s", path, de->d_name);

                /* Skip pg_control here to back up it last */
                if (strcmp(pathbuf, "./global/pg_control") == 0)
                        continue;

                if (lstat(pathbuf, &statbuf) != 0)
                {
                        if (errno != ENOENT)
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not stat file or directory \"%s\": %m",
                                                                pathbuf)));

                        /* If the file went away while scanning, it's not an error. */
                        continue;
                }

                /* Scan for directories whose contents should be excluded */
                excludeFound = false;
                for (excludeIdx = 0; excludeDirContents[excludeIdx] != NULL; excludeIdx++)
                {
                        if (strcmp(de->d_name, excludeDirContents[excludeIdx]) == 0)
                        {
                                elog(DEBUG1, "contents of directory \"%s\" excluded from backup", de->d_name);
                                convert_link_to_directory(pathbuf, &statbuf);
                                size += _tarWriteHeader(sink, pathbuf + basepathlen + 1, NULL,
                                                                                &statbuf, sizeonly);
                                excludeFound = true;
                                break;
                        }
                }

                if (excludeFound)
                        continue;

                /*
                 * Exclude contents of directory specified by statrelpath if not set
                 * to the default (pg_stat_tmp) which is caught in the loop above.
                 */
                if (statrelpath != NULL && strcmp(pathbuf, statrelpath) == 0)
                {
                        elog(DEBUG1, "contents of directory \"%s\" excluded from backup", statrelpath);
                        convert_link_to_directory(pathbuf, &statbuf);
                        size += _tarWriteHeader(sink, pathbuf + basepathlen + 1, NULL,
                                                                        &statbuf, sizeonly);
                        continue;
                }

                /*
                 * We can skip pg_wal, the WAL segments need to be fetched from the
                 * WAL archive anyway. But include it as an empty directory anyway, so
                 * we get permissions right.
                 */
                if (strcmp(pathbuf, "./pg_wal") == 0)
                {
                        /* If pg_wal is a symlink, write it as a directory anyway */
                        convert_link_to_directory(pathbuf, &statbuf);
                        size += _tarWriteHeader(sink, pathbuf + basepathlen + 1, NULL,
                                                                        &statbuf, sizeonly);

                        /*
                         * Also send archive_status directory (by hackishly reusing
                         * statbuf from above ...).
                         */
                        size += _tarWriteHeader(sink, "./pg_wal/archive_status", NULL,
                                                                        &statbuf, sizeonly);

                        continue;                       /* don't recurse into pg_wal */
                }

                /* Allow symbolic links in pg_tblspc only */
                if (strcmp(path, "./pg_tblspc") == 0 &&
#ifndef WIN32
                        S_ISLNK(statbuf.st_mode)
#else
                        pgwin32_is_junction(pathbuf)
#endif
                        )
                {
#if defined(HAVE_READLINK) || defined(WIN32)
                        char            linkpath[MAXPGPATH];
                        int                     rllen;

                        rllen = readlink(pathbuf, linkpath, sizeof(linkpath));
                        if (rllen < 0)
                                ereport(ERROR,
                                                (errcode_for_file_access(),
                                                 errmsg("could not read symbolic link \"%s\": %m",
                                                                pathbuf)));
                        if (rllen >= sizeof(linkpath))
                                ereport(ERROR,
                                                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                                                 errmsg("symbolic link \"%s\" target is too long",
                                                                pathbuf)));
                        linkpath[rllen] = '\0';

                        size += _tarWriteHeader(sink, pathbuf + basepathlen + 1, linkpath,
                                                                        &statbuf, sizeonly);
#else

                        /*
                         * If the platform does not have symbolic links, it should not be
                         * possible to have tablespaces - clearly somebody else created
                         * them. Warn about it and ignore.
                         */
                        ereport(WARNING,
                                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                         errmsg("tablespaces are not supported on this platform")));
                        continue;
#endif                                                  /* HAVE_READLINK */
                }
                else if (S_ISDIR(statbuf.st_mode))
                {
                        bool            skip_this_dir = false;
                        ListCell   *lc;

                        /*
                         * Store a directory entry in the tar file so we can get the
                         * permissions right.
                         */
                        size += _tarWriteHeader(sink, pathbuf + basepathlen + 1, NULL, &statbuf,
                                                                        sizeonly);

                        /*
                         * Call ourselves recursively for a directory, unless it happens
                         * to be a separate tablespace located within PGDATA.
                         */
                        foreach(lc, tablespaces)
                        {
                                tablespaceinfo *ti = (tablespaceinfo *) lfirst(lc);

                                /*
                                 * ti->rpath is the tablespace relative path within PGDATA, or
                                 * NULL if the tablespace has been properly located somewhere
                                 * else.
                                 *
                                 * Skip past the leading "./" in pathbuf when comparing.
                                 */
                                if (ti->rpath && strcmp(ti->rpath, pathbuf + 2) == 0)
                                {
                                        skip_this_dir = true;
                                        break;
                                }
                        }

                        /*
                         * skip sending directories inside pg_tblspc, if not required.
                         */
                        if (strcmp(pathbuf, "./pg_tblspc") == 0 && !sendtblspclinks)
                                skip_this_dir = true;

                        if (!skip_this_dir)
                                size += sendDir(sink, pathbuf, basepathlen, sizeonly, tablespaces,
                                                                sendtblspclinks, manifest, spcoid);
                }
                else if (S_ISREG(statbuf.st_mode))
                {
                        bool            sent = false;

                        if (!sizeonly)
                                sent = sendFile(sink, pathbuf, pathbuf + basepathlen + 1, &statbuf,
                                                                true, isDbDir ? atooid(lastDir + 1) : InvalidOid,
                                                                manifest, spcoid);

                        if (sent || sizeonly)
                        {
                                /* Add size. */
                                size += statbuf.st_size;

                                /* Pad to a multiple of the tar block size. */
                                size += tarPaddingBytesRequired(statbuf.st_size);

                                /* Size of the header for the file. */
                                size += TAR_BLOCK_SIZE;
                        }
                }
                else
                        ereport(WARNING,
                                        (errmsg("skipping special file \"%s\"", pathbuf)));
        }
        FreeDir(dir);
        return size;
}

/*
 * Check if a file should have its checksum validated.
 * We validate checksums on files in regular tablespaces
 * (including global and default) only, and in those there
 * are some files that are explicitly excluded.
 */
static bool
is_checksummed_file(const char *fullpath, const char *filename)
{
        /* Check that the file is in a tablespace */
        if (strncmp(fullpath, "./global/", 9) == 0 ||
                strncmp(fullpath, "./base/", 7) == 0 ||
                strncmp(fullpath, "/", 1) == 0)
        {
                int                     excludeIdx;

                /* Compare file against noChecksumFiles skip list */
                for (excludeIdx = 0; noChecksumFiles[excludeIdx].name != NULL; excludeIdx++)
                {
                        int                     cmplen = strlen(noChecksumFiles[excludeIdx].name);

                        if (!noChecksumFiles[excludeIdx].match_prefix)
                                cmplen++;
                        if (strncmp(filename, noChecksumFiles[excludeIdx].name,
                                                cmplen) == 0)
                                return false;
                }

                return true;
        }
        else
                return false;
}

/*****
 * Functions for handling tar file format
 *
 * Copied from pg_dump, but modified to work with libpq for sending
 */


/*
 * Given the member, write the TAR header & send the file.
 *
 * If 'missing_ok' is true, will not throw an error if the file is not found.
 *
 * If dboid is anything other than InvalidOid then any checksum failures detected
 * will get reported to the stats collector.
 *
 * Returns true if the file was successfully sent, false if 'missing_ok',
 * and the file did not exist.
 */
static bool
sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
                 struct stat *statbuf, bool missing_ok, Oid dboid,
                 backup_manifest_info *manifest, const char *spcoid)
{
        int                     fd;
        BlockNumber blkno = 0;
        bool            block_retry = false;
        uint16          checksum;
        int                     checksum_failures = 0;
        off_t           cnt;
        int                     i;
        pgoff_t         len = 0;
        char       *page;
        PageHeader      phdr;
        int                     segmentno = 0;
        char       *segmentpath;
        bool            verify_checksum = false;
        pg_checksum_context checksum_ctx;

        if (pg_checksum_init(&checksum_ctx, manifest->checksum_type) < 0)
                elog(ERROR, "could not initialize checksum of file \"%s\"",
                         readfilename);

        fd = OpenTransientFile(readfilename, O_RDONLY | PG_BINARY);
        if (fd < 0)
        {
                if (errno == ENOENT && missing_ok)
                        return false;
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not open file \"%s\": %m", readfilename)));
        }

        _tarWriteHeader(sink, tarfilename, NULL, statbuf, false);

        if (!noverify_checksums && DataChecksumsEnabled())
        {
                char       *filename;

                /*
                 * Get the filename (excluding path).  As last_dir_separator()
                 * includes the last directory separator, we chop that off by
                 * incrementing the pointer.
                 */
                filename = last_dir_separator(readfilename) + 1;

                if (is_checksummed_file(readfilename, filename))
                {
                        verify_checksum = true;

                        /*
                         * Cut off at the segment boundary (".") to get the segment number
                         * in order to mix it into the checksum.
                         */
                        segmentpath = strstr(filename, ".");
                        if (segmentpath != NULL)
                        {
                                segmentno = atoi(segmentpath + 1);
                                if (segmentno == 0)
                                        ereport(ERROR,
                                                        (errmsg("invalid segment number %d in file \"%s\"",
                                                                        segmentno, filename)));
                        }
                }
        }

        /*
         * Loop until we read the amount of data the caller told us to expect. The
         * file could be longer, if it was extended while we were sending it, but
         * for a base backup we can ignore such extended data. It will be restored
         * from WAL.
         */
        while (len < statbuf->st_size)
        {
                size_t          remaining = statbuf->st_size - len;

                /* Try to read some more data. */
                cnt = basebackup_read_file(fd, sink->bbs_buffer,
                                                                   Min(sink->bbs_buffer_length, remaining),
                                                                   len, readfilename, true);

                /*
                 * If we hit end-of-file, a concurrent truncation must have occurred.
                 * That's not an error condition, because WAL replay will fix things
                 * up.
                 */
                if (cnt == 0)
                        break;

                /*
                 * The checksums are verified at block level, so we iterate over the
                 * buffer in chunks of BLCKSZ, after making sure that
                 * TAR_SEND_SIZE/buf is divisible by BLCKSZ and we read a multiple of
                 * BLCKSZ bytes.
                 */
                Assert((sink->bbs_buffer_length % BLCKSZ) == 0);

                if (verify_checksum && (cnt % BLCKSZ != 0))
                {
                        ereport(WARNING,
                                        (errmsg("could not verify checksum in file \"%s\", block "
                                                        "%u: read buffer size %d and page size %d "
                                                        "differ",
                                                        readfilename, blkno, (int) cnt, BLCKSZ)));
                        verify_checksum = false;
                }

                if (verify_checksum)
                {
                        for (i = 0; i < cnt / BLCKSZ; i++)
                        {
                                page = sink->bbs_buffer + BLCKSZ * i;

                                /*
                                 * Only check pages which have not been modified since the
                                 * start of the base backup. Otherwise, they might have been
                                 * written only halfway and the checksum would not be valid.
                                 * However, replaying WAL would reinstate the correct page in
                                 * this case. We also skip completely new pages, since they
                                 * don't have a checksum yet.
                                 */
                                if (!PageIsNew(page) && PageGetLSN(page) < sink->bbs_state->startptr)
                                {
                                        checksum = pg_checksum_page((char *) page, blkno + segmentno * RELSEG_SIZE);
                                        phdr = (PageHeader) page;
                                        if (phdr->pd_checksum != checksum)
                                        {
                                                /*
                                                 * Retry the block on the first failure.  It's
                                                 * possible that we read the first 4K page of the
                                                 * block just before postgres updated the entire block
                                                 * so it ends up looking torn to us.  We only need to
                                                 * retry once because the LSN should be updated to
                                                 * something we can ignore on the next pass.  If the
                                                 * error happens again then it is a true validation
                                                 * failure.
                                                 */
                                                if (block_retry == false)
                                                {
                                                        int                     reread_cnt;

                                                        /* Reread the failed block */
                                                        reread_cnt =
                                                                basebackup_read_file(fd,
                                                                                                         sink->bbs_buffer + BLCKSZ * i,
                                                                                                         BLCKSZ, len + BLCKSZ * i,
                                                                                                         readfilename,
                                                                                                         false);
                                                        if (reread_cnt == 0)
                                                        {
                                                                /*
                                                                 * If we hit end-of-file, a concurrent
                                                                 * truncation must have occurred, so break out
                                                                 * of this loop just as if the initial fread()
                                                                 * returned 0. We'll drop through to the same
                                                                 * code that handles that case. (We must fix
                                                                 * up cnt first, though.)
                                                                 */
                                                                cnt = BLCKSZ * i;
                                                                break;
                                                        }

                                                        /* Set flag so we know a retry was attempted */
                                                        block_retry = true;

                                                        /* Reset loop to validate the block again */
                                                        i--;
                                                        continue;
                                                }

                                                checksum_failures++;

                                                if (checksum_failures <= 5)
                                                        ereport(WARNING,
                                                                        (errmsg("checksum verification failed in "
                                                                                        "file \"%s\", block %u: calculated "
                                                                                        "%X but expected %X",
                                                                                        readfilename, blkno, checksum,
                                                                                        phdr->pd_checksum)));
                                                if (checksum_failures == 5)
                                                        ereport(WARNING,
                                                                        (errmsg("further checksum verification "
                                                                                        "failures in file \"%s\" will not "
                                                                                        "be reported", readfilename)));
                                        }
                                }
                                block_retry = false;
                                blkno++;
                        }
                }

                bbsink_archive_contents(sink, cnt);

                /* Also feed it to the checksum machinery. */
                if (pg_checksum_update(&checksum_ctx,
                                                           (uint8 *) sink->bbs_buffer, cnt) < 0)
                        elog(ERROR, "could not update checksum of base backup");

                len += cnt;
        }

        /* If the file was truncated while we were sending it, pad it with zeros */
        while (len < statbuf->st_size)
        {
                size_t          remaining = statbuf->st_size - len;
                size_t          nbytes = Min(sink->bbs_buffer_length, remaining);

                MemSet(sink->bbs_buffer, 0, nbytes);
                if (pg_checksum_update(&checksum_ctx,
                                                           (uint8 *) sink->bbs_buffer,
                                                           nbytes) < 0)
                        elog(ERROR, "could not update checksum of base backup");
                bbsink_archive_contents(sink, nbytes);
                len += nbytes;
        }

        /*
         * Pad to a block boundary, per tar format requirements. (This small piece
         * of data is probably not worth throttling, and is not checksummed
         * because it's not actually part of the file.)
         */
        _tarWritePadding(sink, len);

        CloseTransientFile(fd);

        if (checksum_failures > 1)
        {
                ereport(WARNING,
                                (errmsg_plural("file \"%s\" has a total of %d checksum verification failure",
                                                           "file \"%s\" has a total of %d checksum verification failures",
                                                           checksum_failures,
                                                           readfilename, checksum_failures)));

                pgstat_report_checksum_failures_in_db(dboid, checksum_failures);
        }

        total_checksum_failures += checksum_failures;

        AddFileToBackupManifest(manifest, spcoid, tarfilename, statbuf->st_size,
                                                        (pg_time_t) statbuf->st_mtime, &checksum_ctx);

        return true;
}

static int64
_tarWriteHeader(bbsink *sink, const char *filename, const char *linktarget,
                                struct stat *statbuf, bool sizeonly)
{
        enum tarError rc;

        if (!sizeonly)
        {
                /*
                 * As of this writing, the smallest supported block size is 1kB, which
                 * is twice TAR_BLOCK_SIZE. Since the buffer size is required to be a
                 * multiple of BLCKSZ, it should be safe to assume that the buffer is
                 * large enough to fit an entire tar block. We double-check by means
                 * of these assertions.
                 */
                StaticAssertStmt(TAR_BLOCK_SIZE <= BLCKSZ,
                                                 "BLCKSZ too small for tar block");
                Assert(sink->bbs_buffer_length >= TAR_BLOCK_SIZE);

                rc = tarCreateHeader(sink->bbs_buffer, filename, linktarget,
                                                         statbuf->st_size, statbuf->st_mode,
                                                         statbuf->st_uid, statbuf->st_gid,
                                                         statbuf->st_mtime);

                switch (rc)
                {
                        case TAR_OK:
                                break;
                        case TAR_NAME_TOO_LONG:
                                ereport(ERROR,
                                                (errmsg("file name too long for tar format: \"%s\"",
                                                                filename)));
                                break;
                        case TAR_SYMLINK_TOO_LONG:
                                ereport(ERROR,
                                                (errmsg("symbolic link target too long for tar format: "
                                                                "file name \"%s\", target \"%s\"",
                                                                filename, linktarget)));
                                break;
                        default:
                                elog(ERROR, "unrecognized tar error: %d", rc);
                }

                bbsink_archive_contents(sink, TAR_BLOCK_SIZE);
        }

        return TAR_BLOCK_SIZE;
}

/*
 * Pad with zero bytes out to a multiple of TAR_BLOCK_SIZE.
 */
static void
_tarWritePadding(bbsink *sink, int len)
{
        int                     pad = tarPaddingBytesRequired(len);

        /*
         * As in _tarWriteHeader, it should be safe to assume that the buffer is
         * large enough that we don't need to do this in multiple chunks.
         */
        Assert(sink->bbs_buffer_length >= TAR_BLOCK_SIZE);
        Assert(pad <= TAR_BLOCK_SIZE);

        if (pad > 0)
        {
                MemSet(sink->bbs_buffer, 0, pad);
                bbsink_archive_contents(sink, pad);
        }
}

/*
 * If the entry in statbuf is a link, then adjust statbuf to make it look like a
 * directory, so that it will be written that way.
 */
static void
convert_link_to_directory(const char *pathbuf, struct stat *statbuf)
{
        /* If symlink, write it as a directory anyway */
#ifndef WIN32
        if (S_ISLNK(statbuf->st_mode))
#else
        if (pgwin32_is_junction(pathbuf))
#endif
                statbuf->st_mode = S_IFDIR | pg_dir_create_mode;
}

/*
 * Read some data from a file, setting a wait event and reporting any error
 * encountered.
 *
 * If partial_read_ok is false, also report an error if the number of bytes
 * read is not equal to the number of bytes requested.
 *
 * Returns the number of bytes read.
 */
static int
basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
                                         const char *filename, bool partial_read_ok)
{
        int                     rc;

        pgstat_report_wait_start(WAIT_EVENT_BASEBACKUP_READ);
        rc = pg_pread(fd, buf, nbytes, offset);
        pgstat_report_wait_end();

        if (rc < 0)
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not read file \"%s\": %m", filename)));
        if (!partial_read_ok && rc > 0 && rc != nbytes)
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not read file \"%s\": read %d of %zu",
                                                filename, rc, nbytes)));

        return rc;
}