crimson/os/seastore/lba_manager: allow cloning part of the mapping

Signed-off-by: Xuehan Xu <[email protected]>

Author: xxhdx1985126

src/crimson/os/seastore/lba/btree_lba_manager.cc

@@ -427,17 +427,21 @@ BtreeLBAManager::clone_mapping(
   LBAMapping pos,
   LBAMapping mapping,
   laddr_t laddr,
+  extent_len_t offset,
+  extent_len_t len,
   bool updateref)
 {
   LOG_PREFIX(BtreeLBAManager::clone_mapping);
   assert(pos.is_viewable());
   assert(mapping.is_viewable());
-  DEBUGT("pos={}, mapping={}, laddr={}, updateref={}",
-    t, pos, mapping, laddr, updateref);
+  DEBUGT("pos={}, mapping={}, laddr={}, {}~{} updateref={}",
+    t, pos, mapping, laddr, offset, len, updateref);
+  assert(offset + len <= mapping.get_length());
   struct state_t {
     LBAMapping pos;
     LBAMapping mapping;
     laddr_t laddr;
+    extent_len_t offset;
     extent_len_t len;
   };
   auto c = get_context(t);
@@ -464,11 +468,10 @@ BtreeLBAManager::clone_mapping(
       return update_refcount_iertr::make_ready_future<
 	LBAMapping>(std::move(mapping));
     }
-  }).si_then([c, this, pos=std::move(pos),
-		      laddr](auto mapping) mutable {
-    auto len = mapping.get_length();
+  }).si_then([c, this, pos=std::move(pos), len,
+	      offset, laddr](auto mapping) mutable {
     return seastar::do_with(
-      state_t{std::move(pos), std::move(mapping), laddr, len},
+      state_t{std::move(pos), std::move(mapping), laddr, offset, len},
       [this, c](auto &state) {
       return with_btree<LBABtree>(
 	cache,
@@ -479,17 +482,15 @@ BtreeLBAManager::clone_mapping(
 	).si_then([&state, c, &btree]() mutable {
 	  auto &cursor = state.pos.get_effective_cursor();
 	  assert(state.laddr + state.len <= cursor.key);
+          auto inter_key = state.mapping.is_indirect()
+            ? state.mapping.get_intermediate_key()
+            : state.mapping.get_key();
+          inter_key = (inter_key + state.offset).checked_to_laddr();
 	  return btree.insert(
 	    c,
 	    btree.make_partial_iter(c, cursor),
 	    state.laddr,
-	    lba_map_val_t{
-	      state.len,
-	      state.mapping.is_indirect()
-		? state.mapping.get_intermediate_key()
-		: state.mapping.get_key(),
-	      EXTENT_DEFAULT_REF_COUNT,
-	      0});
+            lba_map_val_t{state.len, inter_key, EXTENT_DEFAULT_REF_COUNT, 0});
 	}).si_then([c, &state](auto p) {
 	  auto &[iter, inserted] = p;
 	  auto &leaf_node = *iter.get_leaf_node();

src/crimson/os/seastore/lba/btree_lba_manager.h

@@ -105,6 +105,8 @@ class BtreeLBAManager : public LBAManager {
     LBAMapping pos,
     LBAMapping mapping,
     laddr_t laddr,
+    extent_len_t offset,
+    extent_len_t len,
     bool updateref) final;
 
 #ifdef UNIT_TESTS_BUILT

src/crimson/os/seastore/lba_manager.h

@@ -117,15 +117,19 @@ class LBAManager {
   using clone_mapping_iertr = alloc_extent_iertr;
   using clone_mapping_ret = clone_mapping_iertr::future<clone_mapping_ret_t>;
   /*
-   * Clones "mapping" at the position "pos" with new laddr "laddr", if updateref
-   * is true, update the refcount of the mapping "mapping"
+   * Clones (part of) "mapping" at the position "pos" with the new lba key "laddr".
    */
   virtual clone_mapping_ret clone_mapping(
     Transaction &t,
-    LBAMapping pos,
-    LBAMapping mapping,
-    laddr_t laddr,
-    bool updateref) = 0;
+    LBAMapping pos,		// the destined position
+    LBAMapping mapping,		// the mapping to be cloned
+    laddr_t laddr,		// the new lba key of the cloned mapping
+    extent_len_t offset,	// the offset of the part to be cloned,
+				// relative to the start of the mapping.
+    extent_len_t len,		// the length of the part to be cloned
+    bool updateref		// whether to update the refcount of the
+				// direct mapping
+  ) = 0;
 
   virtual alloc_extent_ret reserve_region(
     Transaction &t,

src/crimson/os/seastore/transaction_manager.h

@@ -584,24 +584,29 @@ class TransactionManager : public ExtentCallbackInterface {
     LBAMapping pos,
     LBAMapping mapping,
     laddr_t hint,
+    extent_len_t offset,
+    extent_len_t len,
     bool updateref) {
     LOG_PREFIX(TransactionManager::clone_pin);
     SUBDEBUGT(seastore_tm, "{} clone to hint {} ... pos={}, updateref={}",
       t, mapping, hint, pos, updateref);
     return seastar::do_with(
       std::move(pos),
       std::move(mapping),
-      [FNAME, this, &t, hint, updateref](auto &pos, auto &mapping) {
+      [offset, len, FNAME, this, &t, hint, updateref](auto &pos, auto &mapping) {
       return pos.refresh(
       ).si_then([&pos, &mapping](auto m) {
 	pos = std::move(m);
 	return mapping.refresh();
-      }).si_then([FNAME, this, &pos, &t, hint, updateref](auto mapping) {
+      }).si_then([offset, len, FNAME, this, &pos,
+		  &t, hint, updateref](auto mapping) {
 	return lba_manager->clone_mapping(
 	  t,
 	  std::move(pos),
 	  std::move(mapping),
 	  hint,
+	  offset,
+	  len,
 	  updateref
 	).si_then([FNAME, &t](auto ret) {
 	  SUBDEBUGT(seastore_tm, "cloned as {}", t, ret.cloned_mapping);
@@ -664,9 +669,11 @@ class TransactionManager : public ExtentCallbackInterface {
 	if (mapping.is_real()) {
 	  ret = true;
 	}
+	auto len = mapping.get_length();
 	return clone_pin(
 	  t, std::move(pos), std::move(mapping),
-	  (base + offset).checked_to_laddr(), updateref
+	  (base + offset).checked_to_laddr(),
+	  0, len, updateref
 	).si_then([&offset, &pos, &mapping](auto ret) {
 	  offset += ret.cloned_mapping.get_length();
 	  return ret.cloned_mapping.next(

src/test/crimson/seastore/test_transaction_manager.cc

@@ -708,11 +708,14 @@ struct transaction_manager_test_t :
     laddr_t offset) {
     auto key = mapping.get_key();
     auto pin = with_trans_intr(*(t.t), [&](auto &trans) {
+      auto len = mapping.get_length();
       return tm->clone_pin(
 	trans,
 	std::move(pos),
 	std::move(mapping),
 	offset,
+	0,
+	len,
 	true);
     }).unsafe_get().cloned_mapping;
     EXPECT_EQ(offset, pin.get_key());