From b508f64aa492c26c63323d30a7002b48187db19b Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <idryomov@gmail.com>
Date: Tue, 4 Jan 2022 20:38:35 +0100
Subject: [PATCH] librbd: diff-iterate reports incorrect offsets in fast-diff
 mode

If rbd_diff_iterate2() is called on an image offset that doesn't
correspond to an object boundary, the callback is invoked with an
incorrect image offset.  For example, assuming a fully allocated
image, a diff request for 806354944~57344 results in offs=807403520,
len=57344, exists=true invocation, which is ahead by 1048576 bytes.
This occurs only in fast-diff mode, for a diff request on an image
with the fast-diff feature disabled or if whole_object parameter is
set to false the invocation is correct.

This bug goes back to the introduction of fast-diff mode in commit
6d5b969d4206 ("librbd: add diff_iterate2 to API").

Fixes: https://tracker.ceph.com/issues/53784
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit ea07d1e834018c693fc03637d338806f3c2f494f)

Conflicts:
	src/librbd/api/DiffIterate.cc

Cherry-pick notes:
- Octopus still has explicit iterator syntax in for loop for extents
---
 src/librbd/api/DiffIterate.cc  |  9 +++--
 src/test/librbd/test_librbd.cc | 66 ++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/src/librbd/api/DiffIterate.cc b/src/librbd/api/DiffIterate.cc
index 527193b90533c..4318116732dfc 100644
--- a/src/librbd/api/DiffIterate.cc
+++ b/src/librbd/api/DiffIterate.cc
@@ -399,9 +399,12 @@ int DiffIterate<I>::execute() {
           bool updated = (diff_state == object_map::DIFF_STATE_DATA_UPDATED);
           for (std::vector<ObjectExtent>::iterator q = p->second.begin();
                q != p->second.end(); ++q) {
-            r = m_callback(off + q->offset, q->length, updated, m_callback_arg);
-            if (r < 0) {
-              return r;
+            for (auto& be : q->buffer_extents) {
+              r = m_callback(off + be.first, be.second, updated,
+                             m_callback_arg);
+              if (r < 0) {
+                return r;
+              }
             }
           }
         }
diff --git a/src/test/librbd/test_librbd.cc b/src/test/librbd/test_librbd.cc
index 7937dd95d6643..ec6108fd021a5 100644
--- a/src/test/librbd/test_librbd.cc
+++ b/src/test/librbd/test_librbd.cc
@@ -4345,6 +4345,72 @@ TYPED_TEST(DiffIterateTest, DiffIterateParentDiscard)
   ASSERT_TRUE(two.subset_of(diff));
 }
 
+TYPED_TEST(DiffIterateTest, DiffIterateUnalignedSmall)
+{
+  librados::IoCtx ioctx;
+  ASSERT_EQ(0, this->_rados.ioctx_create(this->m_pool_name.c_str(), ioctx));
+
+  {
+    librbd::RBD rbd;
+    librbd::Image image;
+    int order = 0;
+    std::string name = this->get_temp_image_name();
+    ssize_t size = 10 << 20;
+
+    ASSERT_EQ(0, create_image_pp(rbd, ioctx, name.c_str(), size, &order));
+    ASSERT_EQ(0, rbd.open(ioctx, image, name.c_str(), NULL));
+
+    ceph::bufferlist bl;
+    bl.append(std::string(size, '1'));
+    ASSERT_EQ(size, image.write(0, size, bl));
+
+    std::vector<diff_extent> extents;
+    ASSERT_EQ(0, image.diff_iterate2(NULL, 5000005, 1234, true,
+                                     this->whole_object, vector_iterate_cb,
+                                     &extents));
+    ASSERT_EQ(1u, extents.size());
+    ASSERT_EQ(diff_extent(5000005, 1234, true, 0), extents[0]);
+
+    ASSERT_PASSED(this->validate_object_map, image);
+  }
+
+  ioctx.close();
+}
+
+TYPED_TEST(DiffIterateTest, DiffIterateUnaligned)
+{
+  librados::IoCtx ioctx;
+  ASSERT_EQ(0, this->_rados.ioctx_create(this->m_pool_name.c_str(), ioctx));
+
+  {
+    librbd::RBD rbd;
+    librbd::Image image;
+    int order = 22;
+    std::string name = this->get_temp_image_name();
+    ssize_t size = 20 << 20;
+
+    ASSERT_EQ(0, create_image_pp(rbd, ioctx, name.c_str(), size, &order));
+    ASSERT_EQ(0, rbd.open(ioctx, image, name.c_str(), NULL));
+
+    ceph::bufferlist bl;
+    bl.append(std::string(size, '1'));
+    ASSERT_EQ(size, image.write(0, size, bl));
+
+    std::vector<diff_extent> extents;
+    ASSERT_EQ(0, image.diff_iterate2(NULL, 8376263, 4260970, true,
+                                     this->whole_object, vector_iterate_cb,
+                                     &extents));
+    ASSERT_EQ(3u, extents.size());
+    ASSERT_EQ(diff_extent(8376263, 12345, true, 0), extents[0]);
+    ASSERT_EQ(diff_extent(8388608, 4194304, true, 0), extents[1]);
+    ASSERT_EQ(diff_extent(12582912, 54321, true, 0), extents[2]);
+
+    ASSERT_PASSED(this->validate_object_map, image);
+  }
+
+  ioctx.close();
+}
+
 TEST_F(TestLibRBD, ZeroLengthWrite)
 {
   rados_ioctx_t ioctx;
-- 
2.39.5