Re: Side-project feature request for 'hammer mirror-*' functions

[Michael Neumann <mneumann@xxxxxxxx>]

Michael Neumann wrote:
> Matthew Dillon wrote:
> >     If someone has the time, this is a really simple feature request.
> >     Ok, yah, I could do it myself, but I'm going to offer it to others
> >     first and that might save me a little time :-)
> >
> >     It's simple.  If you do a hammer mirror-copy or hammer mirror-stream
> >     to a target HAMMER filesystem the code checks that the target is a 
> > PFS
> >     slave with the same shared UUID as the master's UUID.
> >
> >     I want a feature that asks the user whether he wants to create a
> >     conforming PFS on the target at that point, if the target directory
> >     does not exist, instead of exiting with an error.
> >
> >     i.e. this would take away all the effort of having to create a 
> > pfs-slave
> >     and assign the correct UUID to it.  It takes about 60 seconds and 
> > some
> >     cutting and pasting to do that manually now... not long, but we can
> >     make it ultra convenient.
> >
> >     You would simply run the command and it would ask if you wanted to 
> > create
> >     a new PFS on the target instead of exiting.  You would say 'yes', and
> >     poof, new mirror slave target :-).
>
> Appended is a first patch. I'm unsure if this is the correct way to do
> it, as the protocol is modified, and I think it's not easily possible to
> read "yes" or "no" from the keyboard in mirror-write (when run via ssh).
>
> Funny, when I run mirror-copy several times I get a panic (screenshot 
> appended). I don't think this can be related to my changes...

This appended patch is even easier.

Regards,

  Michael

Index: cmd_mirror.c
===================================================================
RCS file: /home/dcvs/src/sbin/hammer/cmd_mirror.c,v
retrieving revision 1.15
diff -u -r1.15 cmd_mirror.c
--- cmd_mirror.c	9 Sep 2008 23:34:21 -0000	1.15
+++ cmd_mirror.c	10 Oct 2008 15:49:43 -0000
@@ -106,6 +106,11 @@
 	bwcount = 0;
 
 	/*
+	 * Send initial header for the purpose of determining shared-uuid.
+	 */
+	generate_mrec_header(fd, 1, pfs.pfs_id, NULL, NULL);
+
+	/*
 	 * In 2-way mode the target will send us a PFS info packet
 	 * first.  Use the target's current snapshot TID as our default
 	 * begin TID.
@@ -298,6 +303,33 @@
 	fprintf(stderr, "Mirror-read %s succeeded\n", filesystem);
 }
 
+static void
+create_pfs(const char *filesystem, uuid_t *s_uuid)
+{
+	fprintf(stderr, "PFS slave %s does not exist. Do you want" 
+			" to create id? (yes|no) ", filesystem);
+	fflush(stderr);
+	/* XXX: How to read from keyboard? */
+
+	u_int32_t status;
+	char *shared_uuid = NULL;
+	uuid_to_string(s_uuid, &shared_uuid, &status);
+
+	char *cmd = NULL;
+	asprintf(&cmd, "/sbin/hammer pfs-slave '%s' shared-uuid=%s 1>&2",
+		 filesystem, shared_uuid); 
+	free(shared_uuid);
+
+	if (cmd == NULL) {
+		fprintf(stderr, "Failed to alloc memory\n");
+		exit(1);
+	}
+	if (system(cmd) != 0) {
+		fprintf(stderr, "Failed to create PFS\n");
+	}
+	free(cmd);
+}
+
 /*
  * Pipe the mirroring data stream on stdin to the HAMMER VFS, adding
  * some additional packet types to negotiate TID ranges and to verify
@@ -334,6 +366,7 @@
 	struct hammer_ioc_synctid synctid;
 	union hammer_ioc_mrecord_any mrec_tmp;
 	hammer_ioc_mrecord_any_t mrec;
+	struct stat st;
 	int error;
 	int fd;
 	int n;
@@ -351,6 +384,40 @@
 	hammer_key_end_init(&mirror.key_end);
 	mirror.key_end = mirror.key_beg;
 
+	/*
+	 * Read initial packet
+	 */
+	mrec = read_mrecord(0, &error, &pickup);
+	if (mrec == NULL) {
+		if (error == 0)
+			fprintf(stderr, "validate_mrec_header: short read\n");
+		exit(1);
+	}
+	/*
+	 * Validate packet
+	 */
+	if (mrec->head.type == HAMMER_MREC_TYPE_TERM) {
+		return;
+	}
+	if (mrec->head.type != HAMMER_MREC_TYPE_PFSD) {
+		fprintf(stderr, "validate_mrec_header: did not get expected "
+				"PFSD record type\n");
+		exit(1);
+	}
+	if (mrec->head.rec_size != sizeof(mrec->pfs)) {
+		fprintf(stderr, "validate_mrec_header: unexpected payload "
+				"size\n");
+		exit(1);
+	}
+
+	/*
+	 * Create slave PFS if it doesn't yet exist
+	 */
+	if (lstat(filesystem, &st) != 0) {
+		create_pfs(filesystem, &mrec->pfs.pfsd.shared_uuid);
+	}
+	free(mrec); mrec = NULL;
+
 	fd = getpfs(&pfs, filesystem);
 
 	/*