sync: support syncing specified arguments

* m4/jm-macros.m4 (coreutils_MACROS): Check for syncfs().
* man/sync.x: Add references to syncfs, fsync and fdatasync.
* doc/coreutils.texi (sync invocation): Document the new feature.
* src/sync.c: Include "quote.h".
(AUTHORS): Include myself.
(MODE_FILE, MODE_DATA, MODE_FILE_SYSTEM, MODE_SYNC): New enum values.
(long_options): Define.
(sync_arg): New function.
(usage): Describe that arguments are now accepted.
(main): Add arguments parsing and add support for fsync(2),
fdatasync(2) and syncfs(2).
* tests/misc/sync.sh: New (and only) test for sync.
* tests/local.mk: Reference the new test.
* AUTHORS: Add myself to sync's authors.
* NEWS: Mention the new feature.

1 files changed, 165 insertions, 12 deletions

diff --git a/src/sync.c b/src/sync.c
index e9f4d7e8c..b71b8bc21 100644
--- a/src/sync.c
+++ b/src/sync.c
@@ -17,18 +17,42 @@
 /* Written by Jim Meyering */
 
 #include <config.h>
+#include <assert.h>
 #include <getopt.h>
 #include <stdio.h>
 #include <sys/types.h>
 
 #include "system.h"
 #include "error.h"
-#include "long-options.h"
+#include "quote.h"
 
 /* The official name of this program (e.g., no 'g' prefix).  */
 #define PROGRAM_NAME "sync"
 
-#define AUTHORS proper_name ("Jim Meyering")
+#define AUTHORS                                 \
+  proper_name ("Jim Meyering"),                 \
+  proper_name ("Giuseppe Scrivano")
+
+#ifndef HAVE_SYNCFS
+# define HAVE_SYNCFS 0
+#endif
+
+enum sync_mode
+{
+  MODE_FILE,
+  MODE_DATA,
+  MODE_FILE_SYSTEM,
+  MODE_SYNC
+};
+
+static struct option const long_options[] =
+{
+  {"data", no_argument, NULL, 'd'},
+  {"file-system", no_argument, NULL, 'f'},
+  {GETOPT_HELP_OPTION_DECL},
+  {GETOPT_VERSION_OPTION_DECL},
+  {NULL, 0, NULL, 0}
+};
 
 void
 usage (int status)
@@ -37,11 +61,22 @@ usage (int status)
     emit_try_help ();
   else
     {
-      printf (_("Usage: %s [OPTION]\n"), program_name);
+      printf (_("Usage: %s [OPTION] [FILE]...\n"), program_name);
       fputs (_("\
-Force changed blocks to disk, update the super block.\n\
+Synchronize cached writes to persistent storage\n\
+\n\
+If one or more files are specified, sync only them,\n\
+or their containing file systems.\n\
 \n\
 "), stdout);
+
+      fputs (_("\
+  -d, --data             sync only file data, no unneeded metadata\n\
+"), stdout);
+      fputs (_("\
+  -f, --file-system      sync the file systems that contain the files\n\
+"), stdout);
+
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
       emit_ancillary_info (PROGRAM_NAME);
@@ -49,9 +84,86 @@ Force changed blocks to disk, update the super block.\n\
   exit (status);
 }
 
+/* Sync the specified FILE, or file systems associated with FILE.
+   Return 1 on success.  */
+
+static bool
+sync_arg (enum sync_mode mode, char const *file)
+{
+  bool ret = true;
+  int fd;
+
+  /* Note O_PATH might be supported with syncfs(),
+     though as of Linux 3.18 is not.  */
+  if ((fd = open (file, O_RDONLY | O_NONBLOCK)) < 0)
+    {
+      /* Use the O_RDONLY errno, which is significant
+         with directories for example.  */
+      int rd_errno = errno;
+      if ((fd = open (file, O_WRONLY | O_NONBLOCK)) < 0)
+        error (0, rd_errno, _("error opening %s"), quote (file));
+      return false;
+    }
+
+  /* We used O_NONBLOCK above to not hang with fifos,
+     so reset that here.  */
+  int fdflags;
+  if ((fdflags = fcntl (fd, F_GETFL)) == -1
+      || fcntl (fd, F_SETFL, fdflags & ~O_NONBLOCK) < 0)
+    {
+      error (0, errno, _("couldn't reset non-blocking mode %s"), quote (file));
+      ret = false;
+    }
+
+  if (ret == true)
+    {
+      int sync_status;
+
+      switch (mode)
+        {
+        case MODE_DATA:
+          sync_status = fdatasync (fd);
+          break;
+
+        case MODE_FILE:
+          sync_status = fsync (fd);
+          break;
+
+#if HAVE_SYNCFS
+        case MODE_FILE_SYSTEM:
+          sync_status = syncfs (fd);
+          break;
+#endif
+
+        default:
+          assert ("invalid sync_mode");
+        }
+
+      if (sync_status < 0)
+        {
+          error (0, errno, _("error syncing %s"), quote (file));
+          ret = false;
+        }
+    }
+
+  if (close (fd) < 0)
+    {
+      error (0, errno, _("failed to close %s"), quote (file));
+      ret = false;
+    }
+
+  return ret;
+}
+
 int
 main (int argc, char **argv)
 {
+  int c;
+  bool args_specified;
+  bool arg_data = false, arg_file_system = false;
+  enum sync_mode mode;
+  bool ok = true;
+
   initialize_main (&argc, &argv);
   set_program_name (argv[0]);
   setlocale (LC_ALL, "");
@@ -60,14 +172,55 @@ main (int argc, char **argv)
 
   atexit (close_stdout);
 
-  parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE, Version,
-                      usage, AUTHORS, (char const *) NULL);
-  if (getopt_long (argc, argv, "", NULL, NULL) != -1)
-    usage (EXIT_FAILURE);
+  while ((c = getopt_long (argc, argv, "df", long_options, NULL))
+         != -1)
+    {
+      switch (c)
+        {
+        case 'd':
+          arg_data = true;
+          break;
+
+        case 'f':
+          arg_file_system = true;
+          break;
+
+        case_GETOPT_HELP_CHAR;
+
+        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 
-  if (optind < argc)
-    error (0, 0, _("ignoring all arguments"));
+        default:
+          usage (EXIT_FAILURE);
+        }
+    }
+
+  args_specified = optind < argc;
+
+  if (arg_data && arg_file_system)
+    {
+      error (EXIT_FAILURE, 0,
+             _("cannot specify both --data and --file-system"));
+    }
+
+  if (!args_specified && arg_data)
+    error (EXIT_FAILURE, 0, _("--data needs at least one argument"));
+
+  if (! args_specified || (arg_file_system && ! HAVE_SYNCFS))
+    mode = MODE_SYNC;
+  else if (arg_file_system)
+    mode = MODE_FILE_SYSTEM;
+  else if (! arg_data)
+    mode = MODE_FILE;
+  else
+    mode = MODE_DATA;
+
+  if (mode == MODE_SYNC)
+    sync ();
+  else
+    {
+      for (; optind < argc; optind++)
+        ok &= sync_arg (mode, argv[optind]);
+    }
 
-  sync ();
-  return EXIT_SUCCESS;
+  return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 }