tools: libxc: fix Remus failover regression

commit: c2ba706c "tools/libxc: goto correct label on error paths" by Andrew
Cooper broke Remus in Xen 4.4 or earlier versions that has this commit
backported.

With Remus, this jump essentially discards the current incomplete checkpoint
received by the backup and restore backup from the last complete checkpoint.
This is required for Remus to work and this does not break live migration.  It
has been around since Xen 4.0.

CC: Ian Jackson <ian.jackson@eu.citrix.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Acked-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxc/xc_domain_restore.c b/tools/libxc/xc_domain_restore.c
index e73e0a22d3d58116083454c3258ea3fc6ca05e85..b9a56d5c77a267c1ffef058d04d865a019d6a423 100644 (file)
--- a/tools/libxc/xc_domain_restore.c
+++ b/tools/libxc/xc_domain_restore.c
@@ -1783,20 +1783,29 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
 
     if ( pagebuf_get(xch, ctx, &pagebuf, io_fd, dom) ) {
         PERROR("error when buffering batch, finishing");
-        goto out;
+        /*
+         * Remus: discard the current incomplete checkpoint and restore
+         * backup from the last complete checkpoint.
+         */
+        goto finish;
     }
     memset(&tmptail, 0, sizeof(tmptail));
     tmptail.ishvm = hvm;
     if ( buffer_tail(xch, ctx, &tmptail, io_fd, max_vcpu_id, vcpumap,
                      ext_vcpucontext, vcpuextstate_size) < 0 ) {
         ERROR ("error buffering image tail, finishing");
-        goto out;
+        /*
+         * Remus: discard the current incomplete checkpoint and restore
+         * backup from the last complete checkpoint.
+         */
+        goto finish;
     }
     tailbuf_free(&tailbuf);
     memcpy(&tailbuf, &tmptail, sizeof(tailbuf));
 
     goto loadpages;
 
+  /* With Remus: restore from last complete checkpoint */
   finish:
     if ( hvm )
         goto finish_hvm;