basebackup.c

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/*-------------------------------------------------------------------------
 *
 * basebackup.c
 *    code for taking a base backup and streaming it to a standby
 *
 * Portions Copyright (c) 2010-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/backup/basebackup.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <sys/stat.h>
#include <unistd.h>
#include <time.h>
 
#include "access/xlog_internal.h"
#include "access/xlogbackup.h"
#include "backup/backup_manifest.h"
#include "backup/basebackup.h"
#include "backup/basebackup_incremental.h"
#include "backup/basebackup_sink.h"
#include "backup/basebackup_target.h"
#include "catalog/pg_tablespace_d.h"
#include "commands/defrem.h"
#include "common/compression.h"
#include "common/file_perm.h"
#include "common/file_utils.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 "postmaster/walsummarizer.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/ipc.h"
#include "storage/reinit.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/ps_status.h"
#include "utils/relcache.h"
#include "utils/resowner.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;
    bool        incremental;
    uint32      maxrate;
    bool        sendtblspcmapfile;
    bool        send_to_client;
    bool        use_copytblspc;
    BaseBackupTargetHandle *target_handle;
    backup_manifest_option manifest;
    pg_compress_algorithm compression;
    pg_compress_specification compression_specification;
    pg_checksum_type manifest_checksum_type;
} basebackup_options;
 
static int64 sendTablespace(bbsink *sink, char *path, Oid spcoid, bool sizeonly,
                            struct backup_manifest_info *manifest,
                            IncrementalBackupInfo *ib);
static int64 sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
                     List *tablespaces, bool sendtblspclinks,
                     backup_manifest_info *manifest, Oid spcoid,
                     IncrementalBackupInfo *ib);
static bool sendFile(bbsink *sink, const char *readfilename, const char *tarfilename,
                     struct stat *statbuf, bool missing_ok,
                     Oid dboid, Oid spcoid, RelFileNumber relfilenumber,
                     unsigned segno,
                     backup_manifest_info *manifest,
                     unsigned num_incremental_blocks,
                     BlockNumber *incremental_blocks,
                     unsigned truncation_block_length);
static off_t read_file_data_into_buffer(bbsink *sink,
                                        const char *readfilename, int fd,
                                        off_t offset, size_t length,
                                        BlockNumber blkno,
                                        bool verify_checksum,
                                        int *checksum_failures);
static void push_to_sink(bbsink *sink, pg_checksum_context *checksum_ctx,
                         size_t *bytes_done, void *data, size_t length);
static bool verify_page_checksum(Page page, XLogRecPtr start_lsn,
                                 BlockNumber blkno,
                                 uint16 *expected_checksum);
static void sendFileWithContent(bbsink *sink, const char *filename,
                                const char *content, int len,
                                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,
                                IncrementalBackupInfo *ib);
static void parse_basebackup_options(List *options, basebackup_options *opt);
static int  compareWalFileNames(const ListCell *a, const ListCell *b);
static ssize_t 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;
 
/* 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
     * because extensions like pg_stat_statements store data 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},
 
    /*
     * backup_label and tablespace_map should not exist in a running cluster
     * capable of doing an online backup, but exclude them just in case.
     */
    {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}
};
 
/*
 * 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,
                    IncrementalBackupInfo *ib)
{
    bbsink_state state;
    XLogRecPtr  endptr;
    TimeLineID  endtli;
    backup_manifest_info manifest;
    BackupState *backup_state;
    StringInfo  tablespace_map;
 
    /* 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");
 
    backup_started_in_recovery = RecoveryInProgress();
 
    InitializeBackupManifest(&manifest, opt->manifest,
                             opt->manifest_checksum_type);
 
    total_checksum_failures = 0;
 
    /* Allocate backup related variables. */
    backup_state = (BackupState *) palloc0(sizeof(BackupState));
    tablespace_map = makeStringInfo();
 
    basebackup_progress_wait_checkpoint();
    do_pg_backup_start(opt->label, opt->fastcheckpoint, &state.tablespaces,
                       backup_state, tablespace_map);
 
    state.startptr = backup_state->startpoint;
    state.starttli = backup_state->starttli;
 
    /*
     * Once do_pg_backup_start 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_backup_start() and the end of
     * do_pg_backup_stop() should be inside the error cleanup block!
     */
 
    PG_ENSURE_ERROR_CLEANUP(do_pg_abort_backup, BoolGetDatum(false));
    {
        ListCell   *lc;
        tablespaceinfo *newti;
 
        /* If this is an incremental backup, execute preparatory steps. */
        if (ib != NULL)
            PrepareForIncrementalBackup(ib, backup_state);
 
        /* Add a node for the base directory at the end */
        newti = palloc0(sizeof(tablespaceinfo));
        newti->size = -1;
        state.tablespaces = lappend(state.tablespaces, newti);
 
        /*
         * 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, InvalidOid, NULL);
                else
                    tmp->size = sendTablespace(sink, tmp->path, tmp->oid, true,
                                               NULL, 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;
                char       *backup_label;
 
                bbsink_begin_archive(sink, "base.tar");
 
                /* In the main tar, include the backup_label first... */
                backup_label = build_backup_content(backup_state, false);
                sendFileWithContent(sink, BACKUP_LABEL_FILE,
                                    backup_label, -1, &manifest);
                pfree(backup_label);
 
                /* Then the tablespace_map file, if required... */
                if (opt->sendtblspcmapfile)
                {
                    sendFileWithContent(sink, TABLESPACE_MAP,
                                        tablespace_map->data, -1, &manifest);
                    sendtblspclinks = false;
                }
 
                /* Then the bulk of the files... */
                sendDir(sink, ".", 1, false, state.tablespaces,
                        sendtblspclinks, &manifest, InvalidOid, ib);
 
                /* ... 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, InvalidOid,
                         InvalidRelFileNumber, 0, &manifest, 0, NULL, 0);
            }
            else
            {
                char       *archive_name = psprintf("%u.tar", ti->oid);
 
                bbsink_begin_archive(sink, archive_name);
 
                sendTablespace(sink, ti->path, ti->oid, false, &manifest, ib);
            }
 
            /*
             * 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. */
                StaticAssertDecl(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);
        do_pg_backup_stop(backup_state, !opt->nowait);
 
        endptr = backup_state->stoppoint;
        endtli = backup_state->stoptli;
 
        /* Deallocate backup-related variables. */
        destroyStringInfo(tablespace_map);
        pfree(backup_state);
    }
    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;
            ssize_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, "", -1, &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, InvalidOid, InvalidRelFileNumber, 0,
                     &manifest, 0, NULL, 0);
 
            /* unconditionally mark file as archived */
            StatusFilePath(pathbuf, fname, ".done");
            sendFileWithContent(sink, pathbuf, "", -1, &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_incremental = false;
    bool        o_maxrate = false;
    bool        o_tablespace_map = false;
    bool        o_noverify_checksums = false;
    bool        o_manifest = false;
    bool        o_manifest_checksums = false;
    bool        o_target = false;
    bool        o_target_detail = false;
    char       *target_str = NULL;
    char       *target_detail_str = NULL;
    bool        o_compression = false;
    bool        o_compression_detail = false;
    char       *compression_detail_str = NULL;
 
    MemSet(opt, 0, sizeof(*opt));
    opt->manifest = MANIFEST_OPTION_NO;
    opt->manifest_checksum_type = CHECKSUM_TYPE_CRC32C;
    opt->compression = PG_COMPRESSION_NONE;
    opt->compression_specification.algorithm = PG_COMPRESSION_NONE;
 
    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, "incremental") == 0)
        {
            if (o_incremental)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("duplicate option \"%s\"", defel->defname)));
            opt->incremental = defGetBoolean(defel);
            if (opt->incremental && !summarize_wal)
                ereport(ERROR,
                        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                         errmsg("incremental backups cannot be taken unless WAL summarization is enabled")));
            o_incremental = 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 if (strcmp(defel->defname, "target") == 0)
        {
            if (o_target)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("duplicate option \"%s\"", defel->defname)));
            target_str = defGetString(defel);
            o_target = true;
        }
        else if (strcmp(defel->defname, "target_detail") == 0)
        {
            char       *optval = defGetString(defel);
 
            if (o_target_detail)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("duplicate option \"%s\"", defel->defname)));
            target_detail_str = optval;
            o_target_detail = true;
        }
        else if (strcmp(defel->defname, "compression") == 0)
        {
            char       *optval = defGetString(defel);
 
            if (o_compression)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("duplicate option \"%s\"", defel->defname)));
            if (!parse_compress_algorithm(optval, &opt->compression))
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("unrecognized compression algorithm: \"%s\"",
                                optval)));
            o_compression = true;
        }
        else if (strcmp(defel->defname, "compression_detail") == 0)
        {
            if (o_compression_detail)
                ereport(ERROR,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("duplicate option \"%s\"", defel->defname)));
            compression_detail_str = defGetString(defel);
            o_compression_detail = true;
        }
        else
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("unrecognized base backup option: \"%s\"",
                            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;
    }
 
    if (target_str == NULL)
    {
        if (target_detail_str != NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("target detail cannot be used without target")));
        opt->use_copytblspc = true;
        opt->send_to_client = true;
    }
    else if (strcmp(target_str, "client") == 0)
    {
        if (target_detail_str != NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_SYNTAX_ERROR),
                     errmsg("target \"%s\" does not accept a target detail",
                            target_str)));
        opt->send_to_client = true;
    }
    else
        opt->target_handle =
            BaseBackupGetTargetHandle(target_str, target_detail_str);
 
    if (o_compression_detail && !o_compression)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("compression detail cannot be specified unless compression is enabled")));
 
    if (o_compression)
    {
        char       *error_detail;
 
        parse_compress_specification(opt->compression, compression_detail_str,
                                     &opt->compression_specification);
        error_detail =
            validate_compress_specification(&opt->compression_specification);
        if (error_detail != NULL)
            ereport(ERROR,
                    errcode(ERRCODE_SYNTAX_ERROR),
                    errmsg("invalid compression specification: %s",
                           error_detail));
    }
}
 
 
/*
 * SendBaseBackup() - send a complete base backup.
 *
 * The function will put the system into backup mode like pg_backup_start()
 * does, so that the backup is consistent even though we read directly from
 * the filesystem, bypassing the buffer cache.
 */
void
SendBaseBackup(BaseBackupCmd *cmd, IncrementalBackupInfo *ib)
{
    basebackup_options opt;
    bbsink     *sink;
    SessionBackupState status = get_backup_status();
 
    if (status == SESSION_BACKUP_RUNNING)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("a backup is already in progress in this session")));
 
    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);
    }
 
    /*
     * If we're asked to perform an incremental backup and the user has not
     * supplied a manifest, that's an ERROR.
     *
     * If we're asked to perform a full backup and the user did supply a
     * manifest, just ignore it.
     */
    if (!opt.incremental)
        ib = NULL;
    else if (ib == NULL)
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("must UPLOAD_MANIFEST before performing an incremental BASE_BACKUP")));
 
    /*
     * If the target is specifically 'client' then set up to stream the backup
     * to the client; otherwise, it's being sent someplace else and should not
     * be sent to the client. BaseBackupGetSink has the job of setting up a
     * sink to send the backup data wherever it needs to go.
     */
    sink = bbsink_copystream_new(opt.send_to_client);
    if (opt.target_handle != NULL)
        sink = BaseBackupGetSink(opt.target_handle, sink);
 
    /* Set up network throttling, if client requested it */
    if (opt.maxrate > 0)
        sink = bbsink_throttle_new(sink, opt.maxrate);
 
    /* Set up server-side compression, if client requested it */
    if (opt.compression == PG_COMPRESSION_GZIP)
        sink = bbsink_gzip_new(sink, &opt.compression_specification);
    else if (opt.compression == PG_COMPRESSION_LZ4)
        sink = bbsink_lz4_new(sink, &opt.compression_specification);
    else if (opt.compression == PG_COMPRESSION_ZSTD)
        sink = bbsink_zstd_new(sink, &opt.compression_specification);
 
    /* 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, ib);
    }
    PG_FINALLY();
    {
        bbsink_cleanup(sink);
    }
    PG_END_TRY();
}
 
/*
 * Inject a file with given name and content in the output tar stream.
 *
 * "len" can optionally be set to an arbitrary length of data sent.  If set
 * to -1, the content sent is treated as a string with strlen() as length.
 */
static void
sendFileWithContent(bbsink *sink, const char *filename, const char *content,
                    int len, backup_manifest_info *manifest)
{
    struct stat statbuf;
    int         bytes_done = 0;
    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);
 
    if (len < 0)
        len = strlen(content);
 
    /*
     * Construct a stat struct for the 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;
        content += nbytes;
    }
 
    _tarWritePadding(sink, len);
 
    AddFileToBackupManifest(manifest, InvalidOid, 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, Oid spcoid, bool sizeonly,
               backup_manifest_info *manifest, IncrementalBackupInfo *ib)
{
    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, ib);
 
    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,
        Oid spcoid, IncrementalBackupInfo *ib)
{
    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        isRelationDir = false;  /* Does directory contain relations? */
    bool        isGlobalDir = false;
    Oid         dboid = InvalidOid;
    BlockNumber *relative_block_numbers = NULL;
 
    /*
     * Since this array is relatively large, avoid putting it on the stack.
     * But we don't need it at all if this is not an incremental backup.
     */
    if (ib != NULL)
        relative_block_numbers = palloc(sizeof(BlockNumber) * RELSEG_SIZE);
 
    /*
     * 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))
        {
            isRelationDir = true;
            dboid = atooid(lastDir + 1);
        }
    }
    else if (strcmp(path, "./global") == 0)
    {
        isRelationDir = true;
        isGlobalDir = true;
    }
 
    dir = AllocateDir(path);
    while ((de = ReadDir(dir, path)) != NULL)
    {
        int         excludeIdx;
        bool        excludeFound;
        RelFileNumber relfilenumber = InvalidRelFileNumber;
        ForkNumber  relForkNum = InvalidForkNumber;
        unsigned    segno = 0;
        bool        isRelationFile = false;
 
        /* 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;
 
        /* Skip macOS system files */
        if (strcmp(de->d_name, ".DS_Store") == 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_backup_stop() 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;
 
        /*
         * If there could be non-temporary relation files in this directory,
         * try to parse the filename.
         */
        if (isRelationDir)
            isRelationFile =
                parse_filename_for_nontemp_relation(de->d_name,
                                                    &relfilenumber,
                                                    &relForkNum, &segno);
 
        /* Exclude all forks for unlogged tables except the init fork */
        if (isRelationFile && relForkNum != INIT_FORKNUM)
        {
            char        initForkFile[MAXPGPATH];
 
            /*
             * If any other type of fork, check if there is an init fork with
             * the same RelFileNumber. If so, the file can be excluded.
             */
            snprintf(initForkFile, sizeof(initForkFile), "%s/%u_init",
                     path, relfilenumber);
 
            if (lstat(initForkFile, &statbuf) == 0)
            {
                elog(DEBUG2,
                     "unlogged relation file \"%s\" excluded from backup",
                     de->d_name);
 
                continue;
            }
        }
 
        /* Exclude temporary relations */
        if (OidIsValid(dboid) && 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;
 
        /*
         * 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 and summaries directories (by
             * hackishly reusing statbuf from above ...).
             */
            size += _tarWriteHeader(sink, "./pg_wal/archive_status", NULL,
                                    &statbuf, sizeonly);
            size += _tarWriteHeader(sink, "./pg_wal/summaries", NULL,
                                    &statbuf, sizeonly);
 
            continue;           /* don't recurse into pg_wal */
        }
 
        /* Allow symbolic links in pg_tblspc only */
        if (strcmp(path, "./pg_tblspc") == 0 && S_ISLNK(statbuf.st_mode))
        {
            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 (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, ib);
        }
        else if (S_ISREG(statbuf.st_mode))
        {
            bool        sent = false;
            unsigned    num_blocks_required = 0;
            unsigned    truncation_block_length = 0;
            char        tarfilenamebuf[MAXPGPATH * 2];
            char       *tarfilename = pathbuf + basepathlen + 1;
            FileBackupMethod method = BACK_UP_FILE_FULLY;
 
            if (ib != NULL && isRelationFile)
            {
                Oid         relspcoid;
                char       *lookup_path;
 
                if (OidIsValid(spcoid))
                {
                    relspcoid = spcoid;
                    lookup_path = psprintf("pg_tblspc/%u/%s", spcoid,
                                           tarfilename);
                }
                else
                {
                    if (isGlobalDir)
                        relspcoid = GLOBALTABLESPACE_OID;
                    else
                        relspcoid = DEFAULTTABLESPACE_OID;
                    lookup_path = pstrdup(tarfilename);
                }
 
                method = GetFileBackupMethod(ib, lookup_path, dboid, relspcoid,
                                             relfilenumber, relForkNum,
                                             segno, statbuf.st_size,
                                             &num_blocks_required,
                                             relative_block_numbers,
                                             &truncation_block_length);
                if (method == BACK_UP_FILE_INCREMENTALLY)
                {
                    statbuf.st_size =
                        GetIncrementalFileSize(num_blocks_required);
                    snprintf(tarfilenamebuf, sizeof(tarfilenamebuf),
                             "%s/INCREMENTAL.%s",
                             path + basepathlen + 1,
                             de->d_name);
                    tarfilename = tarfilenamebuf;
                }
 
                pfree(lookup_path);
            }
 
            if (!sizeonly)
                sent = sendFile(sink, pathbuf, tarfilename, &statbuf,
                                true, dboid, spcoid,
                                relfilenumber, segno, manifest,
                                num_blocks_required,
                                method == BACK_UP_FILE_INCREMENTALLY ? relative_block_numbers : NULL,
                                truncation_block_length);
 
            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)));
    }
 
    if (relative_block_numbers != NULL)
        pfree(relative_block_numbers);
 
    FreeDir(dir);
    return size;
}
 
/*
 * 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 cumulative stats system.
 *
 * If the file is to be sent incrementally, then num_incremental_blocks
 * should be the number of blocks to be sent, and incremental_blocks
 * an array of block numbers relative to the start of the current segment.
 * If the whole file is to be sent, then incremental_blocks should be NULL,
 * and num_incremental_blocks can have any value, as it will be ignored.
 *
 * 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, Oid spcoid,
         RelFileNumber relfilenumber, unsigned segno,
         backup_manifest_info *manifest, unsigned num_incremental_blocks,
         BlockNumber *incremental_blocks, unsigned truncation_block_length)
{
    int         fd;
    BlockNumber blkno = 0;
    int         checksum_failures = 0;
    off_t       cnt;
    pgoff_t     bytes_done = 0;
    bool        verify_checksum = false;
    pg_checksum_context checksum_ctx;
    int         ibindex = 0;
 
    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);
 
    /*
     * Checksums are verified in multiples of BLCKSZ, so the buffer length
     * should be a multiple of the block size as well.
     */
    Assert((sink->bbs_buffer_length % BLCKSZ) == 0);
 
    /*
     * If we weren't told not to verify checksums, and if checksums are
     * enabled for this cluster, and if this is a relation file, then verify
     * the checksum.
     */
    if (!noverify_checksums && DataChecksumsEnabled() &&
        RelFileNumberIsValid(relfilenumber))
        verify_checksum = true;
 
    /*
     * If we're sending an incremental file, write the file header.
     */
    if (incremental_blocks != NULL)
    {
        unsigned    magic = INCREMENTAL_MAGIC;
        size_t      header_bytes_done = 0;
        char        padding[BLCKSZ];
        size_t      paddinglen;
 
        /* Emit header data. */
        push_to_sink(sink, &checksum_ctx, &header_bytes_done,
                     &magic, sizeof(magic));
        push_to_sink(sink, &checksum_ctx, &header_bytes_done,
                     &num_incremental_blocks, sizeof(num_incremental_blocks));
        push_to_sink(sink, &checksum_ctx, &header_bytes_done,
                     &truncation_block_length, sizeof(truncation_block_length));
        push_to_sink(sink, &checksum_ctx, &header_bytes_done,
                     incremental_blocks,
                     sizeof(BlockNumber) * num_incremental_blocks);
 
        /*
         * Add padding to align header to a multiple of BLCKSZ, but only if
         * the incremental file has some blocks, and the alignment is actually
         * needed (i.e. header is not already a multiple of BLCKSZ). If there
         * are no blocks we don't want to make the file unnecessarily large,
         * as that might make some filesystem optimizations impossible.
         */
        if ((num_incremental_blocks > 0) && (header_bytes_done % BLCKSZ != 0))
        {
            paddinglen = (BLCKSZ - (header_bytes_done % BLCKSZ));
 
            memset(padding, 0, paddinglen);
            bytes_done += paddinglen;
 
            push_to_sink(sink, &checksum_ctx, &header_bytes_done,
                         padding, paddinglen);
        }
 
        /* Flush out any data still in the buffer so it's again empty. */
        if (header_bytes_done > 0)
        {
            bbsink_archive_contents(sink, header_bytes_done);
            if (pg_checksum_update(&checksum_ctx,
                                   (uint8 *) sink->bbs_buffer,
                                   header_bytes_done) < 0)
                elog(ERROR, "could not update checksum of base backup");
        }
 
        /* Update our notion of file position. */
        bytes_done += sizeof(magic);
        bytes_done += sizeof(num_incremental_blocks);
        bytes_done += sizeof(truncation_block_length);
        bytes_done += sizeof(BlockNumber) * num_incremental_blocks;
    }
 
    /*
     * 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 (1)
    {
        /*
         * Determine whether we've read all the data that we need, and if not,
         * read some more.
         */
        if (incremental_blocks == NULL)
        {
            size_t      remaining = statbuf->st_size - bytes_done;
 
            /*
             * If we've read the required number of bytes, then it's time to
             * stop.
             */
            if (bytes_done >= statbuf->st_size)
                break;
 
            /*
             * Read as many bytes as will fit in the buffer, or however many
             * are left to read, whichever is less.
             */
            cnt = read_file_data_into_buffer(sink, readfilename, fd,
                                             bytes_done, remaining,
                                             blkno + segno * RELSEG_SIZE,
                                             verify_checksum,
                                             &checksum_failures);
        }
        else
        {
            BlockNumber relative_blkno;
 
            /*
             * If we've read all the blocks, then it's time to stop.
             */
            if (ibindex >= num_incremental_blocks)
                break;
 
            /*
             * Read just one block, whichever one is the next that we're
             * supposed to include.
             */
            relative_blkno = incremental_blocks[ibindex++];
            cnt = read_file_data_into_buffer(sink, readfilename, fd,
                                             relative_blkno * BLCKSZ,
                                             BLCKSZ,
                                             relative_blkno + segno * RELSEG_SIZE,
                                             verify_checksum,
                                             &checksum_failures);
 
            /*
             * If we get a partial read, that must mean that the relation is
             * being truncated. Ultimately, it should be truncated to a
             * multiple of BLCKSZ, since this path should only be reached for
             * relation files, but we might transiently observe an
             * intermediate value.
             *
             * It should be fine to treat this just as if the entire block had
             * been truncated away - i.e. fill this and all later blocks with
             * zeroes. WAL replay will fix things up.
             */
            if (cnt < BLCKSZ)
                break;
        }
 
        /*
         * If the amount of data we were able to read was not a multiple of
         * BLCKSZ, we cannot verify checksums, which are block-level.
         */
        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 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;
 
        /* Update block number and # of bytes done for next loop iteration. */
        blkno += cnt / BLCKSZ;
        bytes_done += cnt;
 
        /*
         * Make sure incremental files with block data are properly aligned
         * (header is a multiple of BLCKSZ, blocks are BLCKSZ too).
         */
        Assert(!((incremental_blocks != NULL && num_incremental_blocks > 0) &&
                 (bytes_done % BLCKSZ != 0)));
 
        /* Archive the data we just read. */
        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");
    }
 
    /* If the file was truncated while we were sending it, pad it with zeros */
    while (bytes_done < statbuf->st_size)
    {
        size_t      remaining = statbuf->st_size - bytes_done;
        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);
        bytes_done += 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, bytes_done);
 
    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;
}
 
/*
 * Read some more data from the file into the bbsink's buffer, verifying
 * checksums as required.
 *
 * 'offset' is the file offset from which we should begin to read, and
 * 'length' is the amount of data that should be read. The actual amount
 * of data read will be less than the requested amount if the bbsink's
 * buffer isn't big enough to hold it all, or if the underlying file has
 * been truncated. The return value is the number of bytes actually read.
 *
 * 'blkno' is the block number of the first page in the bbsink's buffer
 * relative to the start of the relation.
 *
 * 'verify_checksum' indicates whether we should try to verify checksums
 * for the blocks we read. If we do this, we'll update *checksum_failures
 * and issue warnings as appropriate.
 */
static off_t
read_file_data_into_buffer(bbsink *sink, const char *readfilename, int fd,
                           off_t offset, size_t length, BlockNumber blkno,
                           bool verify_checksum, int *checksum_failures)
{
    off_t       cnt;
    int         i;
    char       *page;
 
    /* Try to read some more data. */
    cnt = basebackup_read_file(fd, sink->bbs_buffer,
                               Min(sink->bbs_buffer_length, length),
                               offset, readfilename, true);
 
    /* Can't verify checksums if read length is not a multiple of BLCKSZ. */
    if (!verify_checksum || (cnt % BLCKSZ) != 0)
        return cnt;
 
    /* Verify checksum for each block. */
    for (i = 0; i < cnt / BLCKSZ; i++)
    {
        int         reread_cnt;
        uint16      expected_checksum;
 
        page = sink->bbs_buffer + BLCKSZ * i;
 
        /* If the page is OK, go on to the next one. */
        if (verify_page_checksum(page, sink->bbs_state->startptr, blkno + i,
                                 &expected_checksum))
            continue;
 
        /*
         * 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. If, before we retry
         * the read, the concurrent write of the block finishes, the page LSN
         * will be updated and we'll realize that we should ignore this block.
         *
         * There's no guarantee that this will actually happen, though: the
         * torn write could take an arbitrarily long time to complete.
         * Retrying multiple times wouldn't fix this problem, either, though
         * it would reduce the chances of it happening in practice. The only
         * real fix here seems to be to have some kind of interlock that
         * allows us to wait until we can be certain that no write to the
         * block is in progress. Since we don't have any such thing right now,
         * we just do this and hope for the best.
         */
        reread_cnt =
            basebackup_read_file(fd, sink->bbs_buffer + BLCKSZ * i,
                                 BLCKSZ, offset + BLCKSZ * i,
                                 readfilename, false);
        if (reread_cnt == 0)
        {
            /*
             * If we hit end-of-file, a concurrent truncation must have
             * occurred, so reduce cnt to reflect only the blocks already
             * processed and break out of this loop.
             */
            cnt = BLCKSZ * i;
            break;
        }
 
        /* If the page now looks OK, go on to the next one. */
        if (verify_page_checksum(page, sink->bbs_state->startptr, blkno + i,
                                 &expected_checksum))
            continue;
 
        /* Handle checksum failure. */
        (*checksum_failures)++;
        if (*checksum_failures <= 5)
            ereport(WARNING,
                    (errmsg("checksum verification failed in "
                            "file \"%s\", block %u: calculated "
                            "%X but expected %X",
                            readfilename, blkno + i, expected_checksum,
                            ((PageHeader) page)->pd_checksum)));
        if (*checksum_failures == 5)
            ereport(WARNING,
                    (errmsg("further checksum verification "
                            "failures in file \"%s\" will not "
                            "be reported", readfilename)));
    }
 
    return cnt;
}
 
/*
 * Push data into a bbsink.
 *
 * It's better, when possible, to read data directly into the bbsink's buffer,
 * rather than using this function to copy it into the buffer; this function is
 * for cases where that approach is not practical.
 *
 * bytes_done should point to a count of the number of bytes that are
 * currently used in the bbsink's buffer. Upon return, the bytes identified by
 * data and length will have been copied into the bbsink's buffer, flushing
 * as required, and *bytes_done will have been updated accordingly. If the
 * buffer was flushed, the previous contents will also have been fed to
 * checksum_ctx.
 *
 * Note that after one or more calls to this function it is the caller's
 * responsibility to perform any required final flush.
 */
static void
push_to_sink(bbsink *sink, pg_checksum_context *checksum_ctx,
             size_t *bytes_done, void *data, size_t length)
{
    while (length > 0)
    {
        size_t      bytes_to_copy;
 
        /*
         * We use < here rather than <= so that if the data exactly fills the
         * remaining buffer space, we trigger a flush now.
         */
        if (length < sink->bbs_buffer_length - *bytes_done)
        {
            /* Append remaining data to buffer. */
            memcpy(sink->bbs_buffer + *bytes_done, data, length);
            *bytes_done += length;
            return;
        }
 
        /* Copy until buffer is full and flush it. */
        bytes_to_copy = sink->bbs_buffer_length - *bytes_done;
        memcpy(sink->bbs_buffer + *bytes_done, data, bytes_to_copy);
        data = ((char *) data) + bytes_to_copy;
        length -= bytes_to_copy;
        bbsink_archive_contents(sink, sink->bbs_buffer_length);
        if (pg_checksum_update(checksum_ctx, (uint8 *) sink->bbs_buffer,
                               sink->bbs_buffer_length) < 0)
            elog(ERROR, "could not update checksum");
        *bytes_done = 0;
    }
}
 
/*
 * Try to verify the checksum for the provided page, if it seems appropriate
 * to do so.
 *
 * Returns true if verification succeeds or if we decide not to check it,
 * and false if verification fails. When return false, it also sets
 * *expected_checksum to the computed value.
 */
static bool
verify_page_checksum(Page page, XLogRecPtr start_lsn, BlockNumber blkno,
                     uint16 *expected_checksum)
{
    PageHeader  phdr;
    uint16      checksum;
 
    /*
     * 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) >= start_lsn)
        return true;
 
    /* Perform the actual checksum calculation. */
    checksum = pg_checksum_page(page, blkno);
 
    /* See whether it matches the value from the page. */
    phdr = (PageHeader) page;
    if (phdr->pd_checksum == checksum)
        return true;
    *expected_checksum = checksum;
    return false;
}
 
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.
         */
        StaticAssertDecl(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 */
    if (S_ISLNK(statbuf->st_mode))
        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 ssize_t
basebackup_read_file(int fd, char *buf, size_t nbytes, off_t offset,
                     const char *filename, bool partial_read_ok)
{
    ssize_t     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 %zd of %zu",
                        filename, rc, nbytes)));
 
    return rc;
}