crostini: Handle the disk resizing case where we are overprovisioned.

In some cases the user could end up with a disk larger than we allow
them to have. When that happens they can still go up to their current
size instead of us erroring out.

Bug: chromium:1083847
Test: Unit
Change-Id: If55591bfbf8d7c81c1aea27db9dc06a54ea0988f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2208157
Auto-Submit: David Munro <davidmunro@google.com>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770018}

chrome/browser/chromeos/crostini/crostini_disk.cc

@@ -124,8 +124,6 @@ void OnListVmDisks(
     std::move(callback).Run(nullptr);
     return;
   }
-  // User has to leave at least kDiskHeadroomBytes for the host system.
-  int64_t max_size = free_space - kDiskHeadroomBytes;
   auto disk_info = std::make_unique<CrostiniDiskInfo>();
   auto image =
       std::find_if(response->images().begin(), response->images().end(),
@@ -152,6 +150,12 @@ void OnListVmDisks(
   if (image->min_size() == 0) {
     VLOG(1) << "Unable to get minimum disk size. VM not running yet?";
   }
+  // User has to leave at least kDiskHeadroomBytes for the host system.
+  // In some cases we can be over-provisioned (e.g. we increased the headroom
+  // required), when that happens the user can still go up to their currently
+  // allocated size.
+  int64_t max_size =
+      std::max(free_space - kDiskHeadroomBytes + image->size(), image->size());
   disk_info->is_user_chosen_size = image->user_chosen_size();
   disk_info->can_resize =
       image->image_type() == vm_tools::concierge::DiskImageType::DISK_IMAGE_RAW;
@@ -160,12 +164,11 @@ void OnListVmDisks(
   const int64_t min_size =
       std::max(static_cast<int64_t>(image->min_size()), kMinimumDiskSizeBytes);
   std::vector<crostini::mojom::DiskSliderTickPtr> ticks =
-      GetTicks(min_size, image->size(), max_size + image->size(),
-               &(disk_info->default_index));
+      GetTicks(min_size, image->size(), max_size, &(disk_info->default_index));
   if (ticks.size() == 0) {
     LOG(ERROR) << "Unable to calculate the number of ticks for min: "
                << min_size << " current: " << image->size()
-               << " max: " << max_size + image->size();
+               << " max: " << max_size;
     std::move(callback).Run(nullptr);
     return;
   }

chrome/browser/chromeos/crostini/crostini_disk_unittest.cc

@@ -263,5 +263,21 @@ TEST_F(CrostiniDiskTestDbus, DiskResizeEventualSuccessReportsSuccess) {
   EXPECT_EQ(result, true);
 }
 
+TEST_F(CrostiniDiskTestDbus, DiskResizeNegativeHeadroom) {
+  vm_tools::concierge::ListVmDisksResponse response;
+  auto* image = response.add_images();
+  response.set_success(true);
+  image->set_name("vm_name");
+  image->set_image_type(vm_tools::concierge::DiskImageType::DISK_IMAGE_RAW);
+  image->set_min_size(1000);
+  image->set_size(3 * kGiB);
+  auto disk_info =
+      OnListVmDisksWithResult("vm_name", kDiskHeadroomBytes - 1, response);
+  ASSERT_TRUE(disk_info);
+
+  ASSERT_TRUE(disk_info->ticks.size() > 0);
+  ASSERT_EQ(disk_info->ticks.at(disk_info->ticks.size() - 1)->value, 3 * kGiB);
+}
+
 }  // namespace disk
 }  // namespace crostini