Merge lp:~colin-king/ubuntu/wily/mountall/zfs-support into lp:ubuntu/wily/mountall

[Colin Ian King]

I am proposing the following ZFS related patches to be merged into mountall. These patches are directly from Ubuntu ZFS on Linux (https://launchpad.net/~zfs-native/+archive/ubuntu/stable) and have considerable time to mature.

[Martin Pitt (pitti)]

Does that actually still make sense as we now have systemd? I doubt zfs is going to be used on phones (where we still use mountall and upstart). Does systemd's fstab generator need changes to generate .mount units for ZFS?

review: Needs Information

[Colin Ian King (colin-king)]

We indeed don't need this now. Please ignore this. Apologies.

[Martin Pitt (pitti)]

No need to apologize, thank you! Sorry that this was in vain.

Unmerged revisions

467. By Colin Ian King on 2015-08-06

* Handle duplicate mountpoints.
When mountall is iterating in try_mounts() on new mount point, change
is_parent() to return false when a record is tested against itself
because a mount point cannot be a root of itself.

Mountall does not preserve the behavior of `mount -a` if more than
one device shares a mountpoint in the /etc/fstab file. Suppose:

        /var/tmp/alfa /mnt/charlie ext2 loop 0 0
        /var/tmp/bravo /mnt/charlie ext2 loop 0 0

Both filesystems are mounted on /mnt/charlie by `mount -a`, but
bravo is ignored by `mountall`. This seems to be an artifact of the fix for
LP: #443035 in zfsonlinux/mountall@eca315d06ae4a2913f9b2ec994c68c45fead912f.

Furthermore, mountall hangs if such mounts are ZFS datasets or A

Closes: zfsonlinux/mountall#5
Darik Horn <email address hidden>, Fri, 27 Mar 2013 22:29:47 -0600

466. By Colin Ian King on 2015-08-06

* no filesystem should depend on mounting swap first
  mk01 <email address hidden>, Fri, 1 Feb 2013 02:06:57 +0100

465. By Colin Ian King on 2015-08-06

* readonly and atime options reflected during mount
  Matus Kral <email address hidden>, Wed, 30 Jan 2013 08:09:00 +0100

464. By Colin Ian King on 2015-08-06

* Disregard the 'mounted' dataset property.
  If `/etc/mtab` is not a symlink to `/proc/mounts`, and if it contains stale
  records, then `zfs list` returns incorrect 'mounted' values that cause
  corresponding datasets to be ignored.

  The mounted check is unnecessary (and the problem), since mountall checks if
  the mountpoints are already mounted before it spawns a mount job - but zfs list
  checks mtab before it's been written by mountall (and any stale mountpoints get
  misrepresented). Removing that check, everything seems to work fine (mounts
  correctly on startup, doesn't overmount things when run from the command line
  in a running session).
  Will Rouesnel <email address hidden>, Thu, 27 Dec 2012 05:59:37 -0600

463. By Colin Ian King on 2015-08-06

* Add ZFS support.
  Pretend that the output of `zfs list` is appended to the `/etc/fstab` file
  Darik Horn <email address hidden>, Sun, 6 Nov 2011 00:00:00 -0500

=== modified file 'src/mountall.c'
--- src/mountall.c	2013-10-08 02:14:58 +0000
+++ src/mountall.c	2015-08-17 16:26:20 +0000
@@ -147,6 +147,7 @@
 };
 
 #define MOUNT_NAME(_mnt) (strcmp ((_mnt)->type, "swap")			\
+			  && strcmp ((_mnt)->type, "zfs")		\
 			  && strcmp ((_mnt)->mountpoint, "none")	\
 			  ? (_mnt)->mountpoint : (_mnt)->device)
 
@@ -180,6 +181,7 @@
 char * cut_options           (const void *parent, Mount *mnt, ...);
 
 void   parse_fstab           (const char *filename);
+void   parse_zfs_list        (void);
 void   parse_mountinfo       (void);
 
 void   parse_filesystems     (void);
@@ -759,6 +761,102 @@
 	endmntent (fstab);
 }
 
+/**
+ * parse_zfs_list:
+ *
+ * Add the output of `/sbin/zfs list` to the internal mounts list
+ * and pretend that these filesystems were in the /etc/fstab file.
+ *
+ * @TODO: Check whether Canonical agrees that libzfs, which is
+ * subject to the CDDL, should get the GPL system library exemption
+ * like it usually does on BSD and Solaris systems.
+ *
+ * @TODO: Subtitute the call to popen with a libzfs routine.
+ *
+ * @TODO: Double-check whether the new src parameter should be NULL
+ * or set to a dummy fstab filename.
+ *
+ **/
+void
+parse_zfs_list (void)
+{
+	nih_local char *buf = NULL;
+	size_t bufsz = 4096;
+	FILE *zfs_stream;
+	const char zfs_command[] =
+	  "/sbin/zfs list -H -t filesystem -o name,mountpoint,canmount,readonly,atime";
+	int zfs_result;
+
+	nih_debug ("parsing ZFS list");
+
+	fflush (stdout);
+	fflush (stderr);
+	zfs_stream = popen (zfs_command, "r");
+
+	if (zfs_stream == NULL) {
+		nih_debug ("popen /sbin/zfs: %s", strerror (errno));
+		return;
+	}
+
+	buf = NIH_MUST (nih_alloc (NULL, bufsz));
+
+	/* Read one line from the pipe into the buffer. */
+	while (fgets (buf, bufsz, zfs_stream) != NULL) {
+		char *saveptr;
+		char *zfs_name, *zfs_mountpoint, *zfs_canmount, *zfs_optatime, *zfs_optronly;
+		nih_local char *zfs_mntoptions = NULL;
+
+		/* If the line didn't fit, then enlarge the buffer and retry. */
+		while ((! strchr (buf, '\n')) && (! feof (zfs_stream))) {
+			buf = NIH_MUST (nih_realloc (buf, NULL, bufsz + 4096));
+			if (! fgets (buf + bufsz - 1, 4097, zfs_stream)) {
+				break;
+			}
+			bufsz += 4096;
+		}
+
+		zfs_name = strtok_r (buf, "\t", &saveptr);
+		if (! zfs_name) {
+			continue;
+		}
+
+		/* ASSERT: mountpoint[0] = '/' OR mountpoint = none | legacy */
+		zfs_mountpoint = strtok_r (NULL, "\t", &saveptr);
+		if (! zfs_mountpoint || zfs_mountpoint[0] != '/') {
+			continue;
+		}
+
+		/* ASSERT: canmount = on | off | noauto */
+		zfs_canmount = strtok_r (NULL, "\t", &saveptr);
+		if (! zfs_canmount || strcmp (zfs_canmount, "on")) {
+			continue;
+		}
+
+		NIH_MUST (nih_strcat (&zfs_mntoptions, NULL, "zfsutil"));
+
+		/* ASSERT: readonly = on | off */
+		zfs_optronly = strtok_r (NULL, "\t", &saveptr);
+		if ( zfs_optronly && strcmp (zfs_optronly, "off") ) {
+			NIH_MUST (nih_strcat (&zfs_mntoptions, NULL, ",ro"));
+		}
+
+		/* ASSERT: atime = on | off */
+		zfs_optatime = strtok_r (NULL, "\t\n", &saveptr);
+		if ( zfs_optatime && strcmp (zfs_optatime, "on") ) {
+			NIH_MUST (nih_strcat (&zfs_mntoptions, NULL, ",noatime"));
+		}
+
+		new_mount (zfs_mountpoint, zfs_name, FALSE, "zfs", zfs_mntoptions, NULL);
+	}
+
+	zfs_result = pclose (zfs_stream);
+
+	if (zfs_result)
+	{
+		nih_debug ("pclose /sbin/zfs: %i %s", zfs_result, strerror (errno));
+	}
+}
+
 static int
 needs_remount (Mount *mnt)
 {
@@ -1046,9 +1144,7 @@
 
 	len = strlen (root);
 	if ((! strncmp (path, root, len))
-	    && ((path[len] == '\0')
-		|| (path[len] == '/')
-		|| (len && path[len-1] == '/')))
+	    && ((path[len] == '/') || (len && path[len-1] == '/')))
 		return TRUE;
 
 	return FALSE;
@@ -1282,7 +1378,8 @@
 		    && strcmp (mnt->device, "none")
 		    && strcmp (mnt->device, mnt->type)
 		    && (mnt->entry.prev != mounts)
-		    && strcmp (((Mount *)mnt->entry.prev)->device, "none")) {
+		    && strcmp (((Mount *)mnt->entry.prev)->device, "none")
+		    && strcmp (((Mount *)mnt->entry.prev)->type, "swap")) {
 			NihListEntry *dep;
 			Mount *       prior;
 
@@ -4023,6 +4120,7 @@
 	 */
 	parse_fstab (BUILTIN_FSTAB);
 	parse_fstab (_PATH_MNTTAB);
+	parse_zfs_list ();
 	parse_mountinfo ();
 
 	/* Apply policy as to what waits for what, etc. */