HAMMER Util - add `mirror-dump header' to retrieve header information from the 
stream

This may be useful when you want to archive PFSes on a HAMMER filesystem
to a non-hammer storage, format the original or a new hard drive, then
restore the PFSes back on, realizing you forgot writing down the shared-uuid's
(OK you probably won't, but I did :)  The output is similar to that of
`hammer pfs-status' command applied to a live PFS, without `PFS #n' line
and the corresponding curly-brace.

---
 sbin/hammer/cmd_mirror.c   |   15 +++++++++++++--
 sbin/hammer/cmd_pseudofs.c |    2 --
 sbin/hammer/hammer.8       |    5 ++++-
 sbin/hammer/hammer.c       |    4 ++--
 sbin/hammer/hammer.h       |    4 ++--
 5 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/sbin/hammer/cmd_mirror.c b/sbin/hammer/cmd_mirror.c
index a17fced..d463858 100644
--- a/sbin/hammer/cmd_mirror.c
+++ b/sbin/hammer/cmd_mirror.c
@@ -717,7 +717,7 @@ again:
 }
 
 void
-hammer_cmd_mirror_dump(void)
+hammer_cmd_mirror_dump(char **av, int ac)
 {
        char *buf = malloc(SERIALBUF_SIZE);
        struct hammer_ioc_mrecord_head pickup;
@@ -726,6 +726,12 @@ hammer_cmd_mirror_dump(void)
        int size;
        int offset;
        int bytes;
+       int header_only = 0;
+
+       if (ac == 1 && strcmp(*av, "header") == 0)
+               header_only = 1;
+       else if (ac != 0)
+               mirror_usage(1);
 
        /*
         * Read and process the PFS header 
@@ -735,6 +741,11 @@ hammer_cmd_mirror_dump(void)
 
        mrec = read_mrecord(0, &error, &pickup);
 
+       if (header_only && mrec != NULL) {
+               dump_pfsd(&mrec->pfs.pfsd);
+               return;
+       }
+
        /*
         * Read and process bulk records
         */
@@ -1406,7 +1417,7 @@ mirror_usage(int code)
                "hammer mirror-read <filesystem> [begin-tid]\n"
                "hammer mirror-read-stream <filesystem> [begin-tid]\n"
                "hammer mirror-write <filesystem>\n"
-               "hammer mirror-dump\n"
+               "hammer mirror-dump [header]\n"
                "hammer mirror-copy [[u...@]host:]<filesystem>"
                                  " [[u...@]host:]<filesystem>\n"
                "hammer mirror-stream [[u...@]host:]<filesystem>"
diff --git a/sbin/hammer/cmd_pseudofs.c b/sbin/hammer/cmd_pseudofs.c
index a987eff..db2beb7 100644
--- a/sbin/hammer/cmd_pseudofs.c
+++ b/sbin/hammer/cmd_pseudofs.c
@@ -38,7 +38,6 @@
 
 static void parse_pfsd_options(char **av, int ac, hammer_pseudofs_data_t pfsd);
 static void init_pfsd(hammer_pseudofs_data_t pfsd, int is_slave);
-static void dump_pfsd(hammer_pseudofs_data_t pfsd);
 static void pseudofs_usage(int code);
 static int getyn(void);
 static int timetosecs(char *str);
@@ -466,7 +465,6 @@ init_pfsd(hammer_pseudofs_data_t pfsd, int is_slave)
                pfsd->mirror_flags |= HAMMER_PFSD_SLAVE;
 }
 
-static
 void
 dump_pfsd(hammer_pseudofs_data_t pfsd)
 {
diff --git a/sbin/hammer/hammer.8 b/sbin/hammer/hammer.8
index 44f6bae..feadd6a 100644
--- a/sbin/hammer/hammer.8
+++ b/sbin/hammer/hammer.8
@@ -762,12 +762,15 @@ configuration field for the two file systems do not match.
 If the target PFS does not exist this command will ask you whether
 you want to create a compatible PFS slave for the target or not.
 .\" ==== mirror-dump ====
-.It Ar mirror-dump
+.It Ar mirror-dump Ar [header]
 A
 .Ar mirror-read
 can be piped into a
 .Ar mirror-dump
 to dump an ASCII representation of the mirroring stream.
+If the keyword
+.Ar header
+is specified, only the header information is shown.
 .\" ==== mirror-copy ====
 .It Ar mirror-copy Ar [[u...@]host:]filesystem Ar [[u...@]host:]filesystem
 This is a shortcut which pipes a
diff --git a/sbin/hammer/hammer.c b/sbin/hammer/hammer.c
index 000bb99..637b302 100644
--- a/sbin/hammer/hammer.c
+++ b/sbin/hammer/hammer.c
@@ -352,7 +352,7 @@ main(int ac, char **av)
                else if (strcmp(av[0], "mirror-stream") == 0)
                        hammer_cmd_mirror_copy(av + 1, ac - 1, 1);
                else if (strcmp(av[0], "mirror-dump") == 0)
-                       hammer_cmd_mirror_dump();
+                       hammer_cmd_mirror_dump(av + 1, ac - 1);
                else
                        usage(1);
                exit(0);
@@ -482,7 +482,7 @@ usage(int exit_code)
                "hammer mirror-read <filesystem> [begin-tid]\n"
                "hammer mirror-read-stream <filesystem> [begin-tid]\n"
                "hammer mirror-write <filesystem>\n"
-               "hammer mirror-dump\n"
+               "hammer mirror-dump [header]\n"
                "hammer mirror-copy [[u...@]host:]<filesystem>"
                                  " [[u...@]host:]<filesystem>\n"
                "hammer mirror-stream [[u...@]host:]<filesystem>"
diff --git a/sbin/hammer/hammer.h b/sbin/hammer/hammer.h
index b0c6bdd..59a9167 100644
--- a/sbin/hammer/hammer.h
+++ b/sbin/hammer/hammer.h
@@ -86,7 +86,7 @@ void hammer_cmd_synctid(char **av, int ac);
 void hammer_cmd_mirror_read(char **av, int ac, int streaming);
 void hammer_cmd_mirror_write(char **av, int ac);
 void hammer_cmd_mirror_copy(char **av, int ac, int streaming);
-void hammer_cmd_mirror_dump(void);
+void hammer_cmd_mirror_dump(char **av, int ac);
 void hammer_cmd_history(const char *offset_str, char **av, int ac);
 void hammer_cmd_blockmap(void);
 void hammer_cmd_reblock(char **av, int ac, int flags);
@@ -111,4 +111,4 @@ void hammer_reset_cycle(void);
 
 int getpfs(struct hammer_ioc_pseudofs_rw *pfs, const char *path);
 void relpfs(int fd, struct hammer_ioc_pseudofs_rw *pfs);
-
+void dump_pfsd(hammer_pseudofs_data_t pfsd);
-- 
1.6.4

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