nbd: Handle blk_getlength() failure

Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-Id: <1424887718-10800-9-git-send-email-mreitz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

blockdev-nbd.c

@@ -105,7 +105,11 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         writable = false;
     }
 
-    exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL);
+    exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
+                         errp);
+    if (!exp) {
+        return;
+    }
 
     nbd_export_set_name(exp, device);
 

include/block/nbd.h

@@ -86,7 +86,8 @@ typedef struct NBDExport NBDExport;
 typedef struct NBDClient NBDClient;
 
 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
-                          uint32_t nbdflags, void (*close)(NBDExport *));
+                          uint32_t nbdflags, void (*close)(NBDExport *),
+                          Error **errp);
 void nbd_export_close(NBDExport *exp);
 void nbd_export_get(NBDExport *exp);
 void nbd_export_put(NBDExport *exp);

nbd.c

@@ -966,7 +966,8 @@ static void blk_aio_detach(void *opaque)
 }
 
 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
-                          uint32_t nbdflags, void (*close)(NBDExport *))
+                          uint32_t nbdflags, void (*close)(NBDExport *),
+                          Error **errp)
 {
     NBDExport *exp = g_malloc0(sizeof(NBDExport));
     exp->refcount = 1;
@@ -974,7 +975,14 @@ NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
     exp->blk = blk;
     exp->dev_offset = dev_offset;
     exp->nbdflags = nbdflags;
-    exp->size = size == -1 ? blk_getlength(blk) : size;
+    exp->size = size < 0 ? blk_getlength(blk) : size;
+    if (exp->size < 0) {
+        error_setg_errno(errp, -exp->size,
+                         "Failed to determine the NBD export's length");
+        goto fail;
+    }
+    exp->size -= exp->size % BDRV_SECTOR_SIZE;
+
     exp->close = close;
     exp->ctx = blk_get_aio_context(blk);
     blk_ref(blk);
@@ -986,6 +994,10 @@ NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
      */
     blk_invalidate_cache(blk, NULL);
     return exp;
+
+fail:
+    g_free(exp);
+    return NULL;
 }
 
 NBDExport *nbd_export_find(const char *name)

qemu-nbd.c

@@ -717,6 +717,10 @@ int main(int argc, char **argv)
 
     bs->detect_zeroes = detect_zeroes;
     fd_size = blk_getlength(blk);
+    if (fd_size < 0) {
+        errx(EXIT_FAILURE, "Failed to determine the image length: %s",
+             strerror(-fd_size));
+    }
 
     if (partition != -1) {
         ret = find_partition(blk, partition, &dev_offset, &fd_size);
@@ -726,7 +730,11 @@ int main(int argc, char **argv)
         }
     }
 
-    exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed);
+    exp = nbd_export_new(blk, dev_offset, fd_size, nbdflags, nbd_export_closed,
+                         &local_err);
+    if (!exp) {
+        errx(EXIT_FAILURE, "%s", error_get_pretty(local_err));
+    }
 
     if (sockpath) {
         fd = unix_socket_incoming(sockpath);