nbdcopy

dirtybitmap

diff --git a/copy/main.c b/copy/main.c
index c0c9421..5da91bd 100644
--- a/copy/main.c
+++ b/copy/main.c
@@ -46,6 +46,8 @@
 
 bool allocated;                     /* --allocated flag */
 unsigned connections = 4;           /* --connections */
+char* context = "base:allocation";  /* -- context */
+bool use_bitmap = false;
 bool target_is_zero;                /* --target-is-zero flag */
 bool extents = true;                /* ! --no-extents flag */
 bool flush;                         /* --flush flag */
@@ -73,7 +75,7 @@ usage (FILE *fp, int exitcode)
 "\n"
 "Copy to and from an NBD server:\n"
 "\n"
-"    nbdcopy [--allocated] [-C N|--connections=N]\n"
+"    nbdcopy [--allocated] [-C N|--connections=N] [-c N|--context=BITMAP_CTX]\n"
 "            [--destination-is-zero|--target-is-zero] [--flush]\n"
 "            [--no-extents] [-p|--progress|--progress=FD]\n"
 "            [--queue-size=N] [--request-size=N] [-R N|--requests=N]\n"
@@ -117,11 +119,12 @@ main (int argc, char *argv[])
     REQUEST_SIZE_OPTION,
     SYNCHRONOUS_OPTION,
   };
-  const char *short_options = "C:pR:S:T:vV";
+  const char *short_options = "c:C:pR:S:T:vV";
   const struct option long_options[] = {
     { "help",                no_argument,       NULL, HELP_OPTION },
     { "long-options",        no_argument,       NULL, LONG_OPTIONS },
     { "allocated",           no_argument,       NULL, ALLOCATED_OPTION },
+    { "context",             required_argument, NULL, 'c' },
     { "connections",         required_argument, NULL, 'C' },
     { "destination-is-zero", no_argument,       NULL, TARGET_IS_ZERO_OPTION },
     { "flush",               no_argument,       NULL, FLUSH_OPTION },
@@ -200,6 +203,11 @@ main (int argc, char *argv[])
       }
       break;
 
+    case 'c':
+      context = optarg;
+      use_bitmap = true;
+      break;
+
     case 'p':
       progress = true;
       if (optarg) {
@@ -460,9 +468,14 @@ main (int argc, char *argv[])
   /* If the source is NBD and we couldn't negotiate meta
    * base:allocation then turn off extents.
    */
-  if (! src->ops->can_extents (src))
+  if (!src->ops->can_extents (src))
     extents = false;
 
+  if ( use_bitmap == true && !src->ops->can_extents(src)) {
+     fprintf(stderr, "error: specified context %s not exposed by ndb server.\n", context);
+     exit(EXIT_FAILURE);
+  }
+
   /* Always set the progress bar to 0% at the start of the copy. */
   progress_bar (0, 1);
 
diff --git a/copy/nbd-ops.c b/copy/nbd-ops.c
index 71ee0a3..e7358ba 100644
--- a/copy/nbd-ops.c
+++ b/copy/nbd-ops.c
@@ -84,7 +84,7 @@ open_one_nbd_handle (struct rw_nbd *rwn)
   }
 
   if (extents && rwn->d == READING &&
-      nbd_add_meta_context (nbd, "base:allocation") == -1) {
+      nbd_add_meta_context (nbd, context) == -1) {
     fprintf (stderr, "%s: %s\n", prog, nbd_get_error ());
     exit (EXIT_FAILURE);
   }
@@ -236,7 +236,7 @@ nbd_ops_can_extents (struct rw *rw)
   struct rw_nbd *rwn = (struct rw_nbd *)rw;
 
   if (rwn->handles.len > 0)
-    return nbd_can_meta_context (rwn->handles.ptr[0], "base:allocation");
+    return nbd_can_meta_context (rwn->handles.ptr[0], context);
   else
     return false;
 }
@@ -502,9 +502,6 @@ add_extent (void *vp, const char *metacontext,
   extent_list *ret = vp;
   size_t i;
 
-  if (strcmp (metacontext, "base:allocation") != 0 || *error)
-    return 0;
-
   for (i = 0; i < nr_entries; i++) {
     struct extent e;
 
@@ -517,6 +514,7 @@ add_extent (void *vp, const char *metacontext,
      * arguments.
      */
     e.zero = (entries[i].flags & LIBNBD_STATE_ZERO) != 0;
+    e.dirty = (entries[i].flags & LIBNBD_STATE_DIRTY) != 0;
 
     if (extent_list_append (ret, e) == -1) {
       perror ("realloc");
diff --git a/copy/nbdcopy.h b/copy/nbdcopy.h
index 465b705..6cd5535 100644
--- a/copy/nbdcopy.h
+++ b/copy/nbdcopy.h
@@ -115,6 +115,7 @@ struct extent {
   uint64_t offset;
   uint64_t length;
   bool zero;
+  bool dirty;
 };
 DEFINE_VECTOR_TYPE (extent_list, struct extent);
 
@@ -228,6 +229,8 @@ extern void asynch_notify_read_write_not_supported (struct rw *rw,
 
 extern bool allocated;
 extern unsigned connections;
+extern char *context;
+extern bool use_bitmap;
 extern bool target_is_zero;
 extern bool extents;
 extern bool flush;
diff --git a/copy/synch-copying.c b/copy/synch-copying.c
index 38888e3..508370c 100644
--- a/copy/synch-copying.c
+++ b/copy/synch-copying.c
@@ -85,6 +85,13 @@ synch_copying (void)
           offset += exts.ptr[i].length;
         }
         else /* data */ {
+          /* in case data for a specified context, ignore clean extents */
+          if (use_bitmap == true) {
+              if( ! exts.ptr[i].dirty) {
+                offset += exts.ptr[i].length;
+                continue;
+              }
+          }
           r = src->ops->synch_read (src, buf, exts.ptr[i].length, offset);
 
           /* These cases should never happen unless the file is

nbdinfo 'nbd+unix:///vdf?socket=/var/tmp/vircpt.83239' --map=qemu:dirty-bitmap:TEST
         0      131072    1  dirty
    131072      983040    0  clean
   1114112       65536    1  dirty
   1179648      917504    0  clean

$ ./nbdcopy  --synchronous 'nbd+unix:///vdf?socket=/var/tmp/vircpt.83239'  full.img
$ qemu-img info full.img 
image: full.img
file format: raw
virtual size: 2 MiB (2097152 bytes)
disk size: 388 KiB
$ ./nbdcopy  --synchronous -c qemu:dirty-bitmap:TEST  'nbd+unix:///vdf?socket=/var/tmp/vircpt.83239'  inc.img
$ qemu-img info inc.img 
image: inc.img
file format: raw
virtual size: 2 MiB (2097152 bytes)
disk size: 192 KiB