fssync-debug: exec DAFS version if DAFS detected

If the user requests something that differs depending on whether the
server is DAFS or not, try to exec the DAFS-enabled fssync-debug
(dafssync-debug) for them.

Based on a conversation with Tom Keiser.

Reviewed-on: http://gerrit.openafs.org/2480
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 1466cd755ce3b48d312fb4404f494934840e586b)

Change-Id: Id87ef70853212f41d2eabbf02bf67e216d9eb43d
Reviewed-on: http://gerrit.openafs.org/4110
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>

diff --git a/src/vol/fssync-debug.c b/src/vol/fssync-debug.c
index 6bd430bda6f14a62e7787c709f51c22e79df7f8b..fcedca899f6d441d777b46a65484b8dee35a2973 100644 (file)
--- a/src/vol/fssync-debug.c
+++ b/src/vol/fssync-debug.c
@@ -83,6 +83,12 @@ struct state {
     struct volop_state * vop;
 };
 
+#ifndef AFS_DEMAND_ATTACH_FS
+/* remember argv/argc for later, if we need to re-exec */
+static char **fssd_argv;
+static int fssd_argc;
+#endif
+
 static int common_prolog(struct cmd_syndesc *, struct state *);
 static int common_volop_prolog(struct cmd_syndesc *, struct state *);
 
@@ -159,6 +165,10 @@ main(int argc, char **argv)
        exit(2);
     }
 
+#ifndef AFS_DEMAND_ATTACH_FS
+    fssd_argv = argv;
+    fssd_argc = argc;
+#endif
 
     ts = cmd_CreateSyntax("online", VolOnline, NULL, "bring a volume online (FSYNC_VOL_ON opcode)");
     VOLOP_PARMS_DECL(ts);
@@ -257,6 +267,47 @@ main(int argc, char **argv)
     exit(err);
 }
 
+#ifdef AFS_DEMAND_ATTACH_FS
+# define dafs_prolog()
+#else
+/* Try to detect if the fileserver is DAFS, and if so, re-exec as the
+ * DAFS-enabled fssync-debug (dafssync_debug). If we fail to detect or
+ * exec, just try to proceed anyway as if the server is not DAFS */
+static void
+dafs_prolog(void)
+{
+    SYNC_response res;
+    SYNC_PROTO_BUF_DECL(res_buf);
+    afs_int32 code;
+    char *dfssd;
+
+    res.payload.len = SYNC_PROTO_MAX_LEN;
+    res.payload.buf = res_buf;
+
+    /* LISTVOLUMES is a no-op; we just want to get the response header flags
+     * to see if the server reports itself as DAFS or not */
+    code = FSYNC_VolOp(0, NULL, FSYNC_VOL_LISTVOLUMES, FSYNC_WHATEVER, &res);
+    if (code) {
+       /* probably failed to contact the fileserver; later code will provide
+        * some warning/error indication */
+       return;
+    }
+
+    if (!(res.hdr.flags & SYNC_FLAG_DAFS_EXTENSIONS)) {
+       /* fileserver is not DAFS, so we don't need to do anything */
+       return;
+    }
+
+    dfssd = afs_exec_alt(fssd_argc, fssd_argv, "da", NULL);
+
+    fprintf(stderr, "\n*** server asserted demand attach extensions, but we failed\n"
+                    "*** to exec a DAFS-enabled fssync-debug '%s' (errno=%d);\n"
+                    "*** attempting to proceed without it.\n\n", dfssd, errno);
+
+    free(dfssd);
+}
+#endif /* !AFS_DEMAND_ATTACH_FS */
+
 static int
 common_prolog(struct cmd_syndesc * as, struct state * state)
 {
@@ -641,6 +692,8 @@ VolQuery(struct cmd_syndesc * as, void * rock)
     int hi, lo;
 #endif
 
+    dafs_prolog();
+
     res.hdr.response_len = sizeof(res.hdr);
     res.payload.buf = res_buf;
     res.payload.len = SYNC_PROTO_MAX_LEN;
@@ -751,9 +804,10 @@ VolQuery(struct cmd_syndesc * as, void * rock)
        }
 #else /* !AFS_DEMAND_ATTACH_FS */
        if (res.hdr.flags & SYNC_FLAG_DAFS_EXTENSIONS) {
-           printf("*** server asserted demand attach extensions. fssync-debug not built to\n");
-           printf("*** recognize those extensions. please recompile fssync-debug if you need\n");
-           printf("*** to dump dafs extended state\n");
+           printf("*** server asserted demand attach extensions. this fssync-debug\n"
+                  "*** is not built to recognize those extensions. please use an\n"
+                  "*** fssync-debug with demand attach if you need to dump dafs\n"
+                  "*** extended state.\n");
        }
 #endif /* !AFS_DEMAND_ATTACH_FS */
        printf("}\n");
@@ -964,6 +1018,8 @@ VnQuery(struct cmd_syndesc * as, void * rock)
     SYNC_response res;
     Vnode v;
 
+    dafs_prolog();
+
     res.hdr.response_len = sizeof(res.hdr);
     res.payload.buf = res_buf;
     res.payload.len = SYNC_PROTO_MAX_LEN;
@@ -997,9 +1053,10 @@ VnQuery(struct cmd_syndesc * as, void * rock)
 
 #ifdef AFS_DEMAND_ATTACH_FS
        if (!(res.hdr.flags & SYNC_FLAG_DAFS_EXTENSIONS)) {
-           printf("*** fssync-debug built to expect demand attach extensions.  server asserted\n");
-           printf("*** that it was not compiled with demand attach turned on.  please recompile\n");
-           printf("*** fssync-debug to match your server\n");
+           printf("*** this fssync-debug is built to expect demand attach extensions.\n"
+                  "*** server asserted that is was not compiled with demand attach.\n"
+                  "*** please use an fssync-debug without demand attach to match your\n"
+                  "*** server.\n");
            goto done;
        }
 
@@ -1008,9 +1065,9 @@ VnQuery(struct cmd_syndesc * as, void * rock)
        printf("\tvn_state        = %s\n", vn_state_to_string(v.vn_state));
 #else
        if (res.hdr.flags & SYNC_FLAG_DAFS_EXTENSIONS) {
-           printf("*** server asserted demand attach extensions. fssync-debug not built to\n");
-           printf("*** recognize those extensions. please recompile fssync-debug if you need\n");
-           printf("*** to dump dafs extended state\n");
+           printf("*** server asserted demand attach extensions. this fssync-debug is not\n"
+                  "*** built to recognize those extensions. please use an fssync-debug\n"
+                  "*** with demand attach to match your server.\n");
            goto done;
        }
 #endif /* !AFS_DEMAND_ATTACH_FS */