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

[Michael Neumann <mneumann@xxxxxxxx>]

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...

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 15:23:55 -0000
@@ -46,8 +46,8 @@
 			 hammer_ioc_mrecord_any_t mrec, int bytes);
 static void generate_mrec_header(int fd, int fdout, int pfs_id,
 			 hammer_tid_t *tid_begp, hammer_tid_t *tid_endp);
-static int validate_mrec_header(int fd, int fdin, int is_target, int pfs_id,
-			 struct hammer_ioc_mrecord_head *pickup,
+static int validate_mrec_header(int fd, hammer_ioc_mrecord_any_t mrec, 
+			 int is_target, int pfs_id,
 			 hammer_tid_t *tid_begp, hammer_tid_t *tid_endp);
 static void update_pfs_snapshot(int fd, hammer_tid_t snapshot_tid, int pfs_id);
 static ssize_t writebw(int fd, const void *buf, size_t nbytes,
@@ -106,14 +106,26 @@
 	bwcount = 0;
 
 	/*
+	 * Send initial header for the purpose to determine 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.
 	 */
 	mirror.tid_beg = 0;
 	if (TwoWayPipeOpt) {
-		n = validate_mrec_header(fd, 0, 0, pfs.pfs_id, &pickup,
+		mrec = read_mrecord(0, &error, &pickup);
+		if (mrec == NULL) {
+			if (error == 0)
+				fprintf(stderr, "validate_mrec_header: short read\n");
+			exit(1);
+		}
+		n = validate_mrec_header(fd, mrec, 0, pfs.pfs_id, 
 					 NULL, &mirror.tid_beg);
+		free(mrec); mrec = NULL;
 		if (n < 0) {	/* got TERM record */
 			relpfs(fd, &pfs);
 			return;
@@ -298,6 +310,33 @@
 	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
@@ -337,6 +376,7 @@
 	int error;
 	int fd;
 	int n;
+	struct stat st;
 
 	if (ac != 1)
 		mirror_usage(1);
@@ -351,6 +391,42 @@
 	hammer_key_end_init(&mirror.key_end);
 	mirror.key_end = mirror.key_beg;
 
+	/*
+	 * Read initial packet
+	 */
+	mrec = read_mrecord(0, &error, &pickup);
+	pickup.signature = 0;
+	pickup.type = 0;
+	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);
 
 	/*
@@ -368,8 +444,15 @@
 	 * Read and process the PFS header.  The source informs us of
 	 * the TID range the stream represents.
 	 */
-	n = validate_mrec_header(fd, 0, 1, pfs.pfs_id, &pickup,
+	mrec = read_mrecord(0, &error, &pickup);
+	if (mrec == NULL) {
+		if (error == 0)
+			fprintf(stderr, "validate_mrec_header: short read\n");
+		exit(1);
+	}
+	n = validate_mrec_header(fd, mrec, 1, pfs.pfs_id, 
 				 &mirror.tid_beg, &mirror.tid_end);
+	free(mrec); mrec = NULL; 
 	if (n < 0) {	/* got TERM record */
 		relpfs(fd, &pfs);
 		return;
@@ -948,14 +1031,12 @@
  * return -1 if we got a TERM record
  */
 static int
-validate_mrec_header(int fd, int fdin, int is_target, int pfs_id,
-		     struct hammer_ioc_mrecord_head *pickup,
+validate_mrec_header(int fd, hammer_ioc_mrecord_any_t mrec, 
+		     int is_target, int pfs_id,
 		     hammer_tid_t *tid_begp, hammer_tid_t *tid_endp)
 {
 	struct hammer_ioc_pseudofs_rw pfs;
 	struct hammer_pseudofs_data pfsd;
-	hammer_ioc_mrecord_any_t mrec;
-	int error;
 
 	/*
 	 * Get the PFSD info from the target filesystem.
@@ -973,18 +1054,9 @@
 		fprintf(stderr, "mirror-write: HAMMER pfs version mismatch!\n");
 		exit(1);
 	}
-
-	mrec = read_mrecord(fdin, &error, pickup);
-	if (mrec == NULL) {
-		if (error == 0)
-			fprintf(stderr, "validate_mrec_header: short read\n");
-		exit(1);
-	}
 	if (mrec->head.type == HAMMER_MREC_TYPE_TERM) {
-		free(mrec);
 		return(-1);
 	}
-
 	if (mrec->head.type != HAMMER_MREC_TYPE_PFSD) {
 		fprintf(stderr, "validate_mrec_header: did not get expected "
 				"PFSD record type\n");
@@ -1019,7 +1091,6 @@
 		*tid_begp = mrec->pfs.pfsd.sync_beg_tid;
 	if (tid_endp)
 		*tid_endp = mrec->pfs.pfsd.sync_end_tid;
-	free(mrec);
 	return(0);
 }