Move fsync routines of initdb into src/common/

The intention is to used those in other utilities such as pg_basebackup
and pg_receivexlog.

From: Michael Paquier <michael.paquier@gmail.com>

1 files changed, 276 insertions, 0 deletions

diff --git a/src/common/file_utils.c b/src/common/file_utils.c
new file mode 100644
index 00000000000..b6f62f7bf14
--- /dev/null
+++ b/src/common/file_utils.c
@@ -0,0 +1,276 @@
+/*-------------------------------------------------------------------------
+ *
+ * File-processing utility routines.
+ *
+ * Assorted utility functions to work on files.
+ *
+ *
+ * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/common/file_utils.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres_fe.h"
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "common/file_utils.h"
+
+
+/* Define PG_FLUSH_DATA_WORKS if we have an implementation for pg_flush_data */
+#if defined(HAVE_SYNC_FILE_RANGE)
+#define PG_FLUSH_DATA_WORKS 1
+#elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
+#define PG_FLUSH_DATA_WORKS 1
+#endif
+
+#ifdef PG_FLUSH_DATA_WORKS
+static void pre_sync_fname(const char *fname, bool isdir,
+						   const char *progname);
+#endif
+static void walkdir(const char *path,
+	void (*action) (const char *fname, bool isdir, const char *progname),
+	bool process_symlinks, const char *progname);
+
+/*
+ * Issue fsync recursively on PGDATA and all its contents.
+ *
+ * We fsync regular files and directories wherever they are, but we
+ * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * Other symlinks are presumed to point at files we're not responsible
+ * for fsyncing, and might not have privileges to write at all.
+ *
+ * Errors are reported but not considered fatal.
+ */
+void
+fsync_pgdata(const char *pg_data, const char *progname)
+{
+	bool		xlog_is_symlink;
+	char		pg_xlog[MAXPGPATH];
+	char		pg_tblspc[MAXPGPATH];
+
+	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
+
+	/*
+	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * because the first walkdir below will ignore it.
+	 */
+	xlog_is_symlink = false;
+
+#ifndef WIN32
+	{
+		struct stat st;
+
+		if (lstat(pg_xlog, &st) < 0)
+			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
+					progname, pg_xlog, strerror(errno));
+		else if (S_ISLNK(st.st_mode))
+			xlog_is_symlink = true;
+	}
+#else
+	if (pgwin32_is_junction(pg_xlog))
+		xlog_is_symlink = true;
+#endif
+
+	/*
+	 * If possible, hint to the kernel that we're soon going to fsync the data
+	 * directory and its contents.
+	 */
+#ifdef PG_FLUSH_DATA_WORKS
+	walkdir(pg_data, pre_sync_fname, false, progname);
+	if (xlog_is_symlink)
+		walkdir(pg_xlog, pre_sync_fname, false, progname);
+	walkdir(pg_tblspc, pre_sync_fname, true, progname);
+#endif
+
+	/*
+	 * Now we do the fsync()s in the same order.
+	 *
+	 * The main call ignores symlinks, so in addition to specially processing
+	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * process_symlinks = true.  Note that if there are any plain directories
+	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
+	 * so we don't worry about optimizing it.
+	 */
+	walkdir(pg_data, fsync_fname, false, progname);
+	if (xlog_is_symlink)
+		walkdir(pg_xlog, fsync_fname, false, progname);
+	walkdir(pg_tblspc, fsync_fname, true, progname);
+}
+
+/*
+ * walkdir: recursively walk a directory, applying the action to each
+ * regular file and directory (including the named directory itself).
+ *
+ * If process_symlinks is true, the action and recursion are also applied
+ * to regular files and directories that are pointed to by symlinks in the
+ * given directory; otherwise symlinks are ignored.  Symlinks are always
+ * ignored in subdirectories, ie we intentionally don't pass down the
+ * process_symlinks flag to recursive calls.
+ *
+ * Errors are reported but not considered fatal.
+ *
+ * See also walkdir in fd.c, which is a backend version of this logic.
+ */
+static void
+walkdir(const char *path,
+		void (*action) (const char *fname, bool isdir, const char *progname),
+		bool process_symlinks, const char *progname)
+{
+	DIR		   *dir;
+	struct dirent *de;
+
+	dir = opendir(path);
+	if (dir == NULL)
+	{
+		fprintf(stderr, _("%s: could not open directory \"%s\": %s\n"),
+				progname, path, strerror(errno));
+		return;
+	}
+
+	while (errno = 0, (de = readdir(dir)) != NULL)
+	{
+		char		subpath[MAXPGPATH];
+		struct stat fst;
+		int			sret;
+
+		if (strcmp(de->d_name, ".") == 0 ||
+			strcmp(de->d_name, "..") == 0)
+			continue;
+
+		snprintf(subpath, MAXPGPATH, "%s/%s", path, de->d_name);
+
+		if (process_symlinks)
+			sret = stat(subpath, &fst);
+		else
+			sret = lstat(subpath, &fst);
+
+		if (sret < 0)
+		{
+			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
+					progname, subpath, strerror(errno));
+			continue;
+		}
+
+		if (S_ISREG(fst.st_mode))
+			(*action) (subpath, false, progname);
+		else if (S_ISDIR(fst.st_mode))
+			walkdir(subpath, action, false, progname);
+	}
+
+	if (errno)
+		fprintf(stderr, _("%s: could not read directory \"%s\": %s\n"),
+				progname, path, strerror(errno));
+
+	(void) closedir(dir);
+
+	/*
+	 * It's important to fsync the destination directory itself as individual
+	 * file fsyncs don't guarantee that the directory entry for the file is
+	 * synced.  Recent versions of ext4 have made the window much wider but
+	 * it's been an issue for ext3 and other filesystems in the past.
+	 */
+	(*action) (path, true, progname);
+}
+
+/*
+ * Hint to the OS that it should get ready to fsync() this file.
+ *
+ * Ignores errors trying to open unreadable files, and reports other errors
+ * non-fatally.
+ */
+#ifdef PG_FLUSH_DATA_WORKS
+
+static void
+pre_sync_fname(const char *fname, bool isdir, const char *progname)
+{
+	int			fd;
+
+	fd = open(fname, O_RDONLY | PG_BINARY);
+
+	if (fd < 0)
+	{
+		if (errno == EACCES || (isdir && errno == EISDIR))
+			return;
+		fprintf(stderr, _("%s: could not open file \"%s\": %s\n"),
+				progname, fname, strerror(errno));
+		return;
+	}
+
+	/*
+	 * We do what pg_flush_data() would do in the backend: prefer to use
+	 * sync_file_range, but fall back to posix_fadvise.  We ignore errors
+	 * because this is only a hint.
+	 */
+#if defined(HAVE_SYNC_FILE_RANGE)
+	(void) sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WRITE);
+#elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
+	(void) posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
+#else
+#error PG_FLUSH_DATA_WORKS should not have been defined
+#endif
+
+	(void) close(fd);
+}
+
+#endif   /* PG_FLUSH_DATA_WORKS */
+
+/*
+ * fsync_fname -- Try to fsync a file or directory
+ *
+ * Ignores errors trying to open unreadable files, or trying to fsync
+ * directories on systems where that isn't allowed/required.  Reports
+ * other errors non-fatally.
+ */
+void
+fsync_fname(const char *fname, bool isdir, const char *progname)
+{
+	int			fd;
+	int			flags;
+	int			returncode;
+
+	/*
+	 * Some OSs require directories to be opened read-only whereas other
+	 * systems don't allow us to fsync files opened read-only; so we need both
+	 * cases here.  Using O_RDWR will cause us to fail to fsync files that are
+	 * not writable by our userid, but we assume that's OK.
+	 */
+	flags = PG_BINARY;
+	if (!isdir)
+		flags |= O_RDWR;
+	else
+		flags |= O_RDONLY;
+
+	/*
+	 * Open the file, silently ignoring errors about unreadable files (or
+	 * unsupported operations, e.g. opening a directory under Windows), and
+	 * logging others.
+	 */
+	fd = open(fname, flags);
+	if (fd < 0)
+	{
+		if (errno == EACCES || (isdir && errno == EISDIR))
+			return;
+		fprintf(stderr, _("%s: could not open file \"%s\": %s\n"),
+				progname, fname, strerror(errno));
+		return;
+	}
+
+	returncode = fsync(fd);
+
+	/*
+	 * Some OSes don't allow us to fsync directories at all, so we can ignore
+	 * those errors. Anything else needs to be reported.
+	 */
+	if (returncode != 0 && !(isdir && errno == EBADF))
+		fprintf(stderr, _("%s: could not fsync file \"%s\": %s\n"),
+				progname, fname, strerror(errno));
+
+	(void) close(fd);
+}