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Add support for syncfs() in frontend support functions.
This commit adds support for using syncfs() in fsync_pgdata() and fsync_dir_recurse() (which have been renamed to sync_pgdata() and sync_dir_recurse()). Like recovery_init_sync_method, sync_pgdata() calls syncfs() for the data directory, each tablespace, and pg_wal (if it is a symlink). For now, all of the frontend utilities that use these support functions are hard-coded to use fsync(), but a follow-up commit will allow specifying syncfs(). Co-authored-by: Justin Pryzby Reviewed-by: Michael Paquier Discussion: https://postgr.es/m/20210930004340.GM831%40telsasoft.com
This commit is contained in:
Nathan Bossart
@@ -51,19 +51,52 @@ static void walkdir(const char *path,
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int (*action) (const char *fname, bool isdir),
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bool process_symlinks);
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#ifdef HAVE_SYNCFS
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/*
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* Issue fsync recursively on PGDATA and all its contents.
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* do_syncfs -- Try to syncfs a file system
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*
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* We fsync regular files and directories wherever they are, but we follow
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* Reports errors trying to open the path. syncfs() errors are fatal.
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*/
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static void
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do_syncfs(const char *path)
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{
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int fd;
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fd = open(path, O_RDONLY, 0);
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if (fd < 0)
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{
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pg_log_error("could not open file \"%s\": %m", path);
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return;
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}
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if (syncfs(fd) < 0)
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{
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pg_log_error("could not synchronize file system for file \"%s\": %m", path);
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(void) close(fd);
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exit(EXIT_FAILURE);
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}
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(void) close(fd);
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}
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#endif /* HAVE_SYNCFS */
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/*
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* Synchronize PGDATA and all its contents.
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*
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* We sync regular files and directories wherever they are, but we follow
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* symlinks only for pg_wal (or pg_xlog) and immediately under pg_tblspc.
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* Other symlinks are presumed to point at files we're not responsible for
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* fsyncing, and might not have privileges to write at all.
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* syncing, and might not have privileges to write at all.
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*
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* serverVersion indicates the version of the server to be fsync'd.
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* serverVersion indicates the version of the server to be sync'd.
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*/
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void
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fsync_pgdata(const char *pg_data,
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int serverVersion)
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sync_pgdata(const char *pg_data,
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int serverVersion,
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DataDirSyncMethod sync_method)
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{
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bool xlog_is_symlink;
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char pg_wal[MAXPGPATH];
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@@ -89,49 +122,135 @@ fsync_pgdata(const char *pg_data,
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xlog_is_symlink = true;
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}
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/*
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* If possible, hint to the kernel that we're soon going to fsync the data
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* directory and its contents.
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*/
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switch (sync_method)
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{
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case DATA_DIR_SYNC_METHOD_SYNCFS:
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{
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#ifndef HAVE_SYNCFS
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pg_log_error("this build does not support sync method \"%s\"",
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"syncfs");
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exit(EXIT_FAILURE);
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#else
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DIR *dir;
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struct dirent *de;
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/*
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* On Linux, we don't have to open every single file one by
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* one. We can use syncfs() to sync whole filesystems. We
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* only expect filesystem boundaries to exist where we
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* tolerate symlinks, namely pg_wal and the tablespaces, so we
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* call syncfs() for each of those directories.
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*/
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/* Sync the top level pgdata directory. */
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do_syncfs(pg_data);
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/* If any tablespaces are configured, sync each of those. */
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dir = opendir(pg_tblspc);
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if (dir == NULL)
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pg_log_error("could not open directory \"%s\": %m",
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pg_tblspc);
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else
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{
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while (errno = 0, (de = readdir(dir)) != NULL)
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{
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char subpath[MAXPGPATH * 2];
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if (strcmp(de->d_name, ".") == 0 ||
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strcmp(de->d_name, "..") == 0)
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continue;
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snprintf(subpath, sizeof(subpath), "%s/%s",
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pg_tblspc, de->d_name);
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do_syncfs(subpath);
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}
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if (errno)
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pg_log_error("could not read directory \"%s\": %m",
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pg_tblspc);
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(void) closedir(dir);
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}
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/* If pg_wal is a symlink, process that too. */
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if (xlog_is_symlink)
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do_syncfs(pg_wal);
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#endif /* HAVE_SYNCFS */
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}
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break;
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case DATA_DIR_SYNC_METHOD_FSYNC:
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{
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/*
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* If possible, hint to the kernel that we're soon going to
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* fsync the data directory and its contents.
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*/
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#ifdef PG_FLUSH_DATA_WORKS
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walkdir(pg_data, pre_sync_fname, false);
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if (xlog_is_symlink)
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walkdir(pg_wal, pre_sync_fname, false);
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walkdir(pg_tblspc, pre_sync_fname, true);
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walkdir(pg_data, pre_sync_fname, false);
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if (xlog_is_symlink)
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walkdir(pg_wal, pre_sync_fname, false);
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walkdir(pg_tblspc, pre_sync_fname, true);
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#endif
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/*
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* Now we do the fsync()s in the same order.
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*
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* The main call ignores symlinks, so in addition to specially processing
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* pg_wal if it's a symlink, pg_tblspc has to be visited separately with
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* process_symlinks = true. Note that if there are any plain directories
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* in pg_tblspc, they'll get fsync'd twice. That's not an expected case
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* so we don't worry about optimizing it.
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*/
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walkdir(pg_data, fsync_fname, false);
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if (xlog_is_symlink)
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walkdir(pg_wal, fsync_fname, false);
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walkdir(pg_tblspc, fsync_fname, true);
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/*
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* Now we do the fsync()s in the same order.
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*
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* The main call ignores symlinks, so in addition to specially
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* processing pg_wal if it's a symlink, pg_tblspc has to be
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* visited separately with process_symlinks = true. Note that
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* if there are any plain directories in pg_tblspc, they'll
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* get fsync'd twice. That's not an expected case so we don't
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* worry about optimizing it.
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*/
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walkdir(pg_data, fsync_fname, false);
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if (xlog_is_symlink)
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walkdir(pg_wal, fsync_fname, false);
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walkdir(pg_tblspc, fsync_fname, true);
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}
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break;
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}
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}
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/*
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* Issue fsync recursively on the given directory and all its contents.
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* Synchronize the given directory and all its contents.
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*
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* This is a convenient wrapper on top of walkdir().
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* This is a convenient wrapper on top of walkdir() and do_syncfs().
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*/
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void
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fsync_dir_recurse(const char *dir)
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sync_dir_recurse(const char *dir, DataDirSyncMethod sync_method)
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{
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/*
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* If possible, hint to the kernel that we're soon going to fsync the data
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* directory and its contents.
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*/
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switch (sync_method)
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{
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case DATA_DIR_SYNC_METHOD_SYNCFS:
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{
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#ifndef HAVE_SYNCFS
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pg_log_error("this build does not support sync method \"%s\"",
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"syncfs");
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exit(EXIT_FAILURE);
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#else
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/*
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* On Linux, we don't have to open every single file one by
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* one. We can use syncfs() to sync the whole filesystem.
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*/
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do_syncfs(dir);
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#endif /* HAVE_SYNCFS */
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}
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break;
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case DATA_DIR_SYNC_METHOD_FSYNC:
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{
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/*
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* If possible, hint to the kernel that we're soon going to
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* fsync the data directory and its contents.
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*/
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#ifdef PG_FLUSH_DATA_WORKS
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walkdir(dir, pre_sync_fname, false);
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walkdir(dir, pre_sync_fname, false);
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#endif
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walkdir(dir, fsync_fname, false);
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walkdir(dir, fsync_fname, false);
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}
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break;
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}
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}
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/*
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