crimson/os/seastore/cache: do `prepare_commit` before retiring extents

Linked tree nodes in logical trees need to take parents from the prior
instances when being rewritten, which has to be done before the prior
instances are retired.

Signed-off-by: Xuehan Xu <xuxuehan@qianxin.com>

diff --git a/src/crimson/os/seastore/cache.cc b/src/crimson/os/seastore/cache.cc
index d94193f8176d9f0d5f6613135e46022f10839c34..53b23025cd6655475a00866b55611b259ed49e4d 100644 (file)
--- a/src/crimson/os/seastore/cache.cc
+++ b/src/crimson/os/seastore/cache.cc
@@ -1340,6 +1340,14 @@ record_t Cache::prepare_record(
     delta_stat.increment(delta_length);
   }
 
+  t.for_each_finalized_fresh_block([](auto &e) {
+    // fresh blocks' `prepare_commit` must be invoked before
+    // retiering extents, this is because logical linked tree
+    // nodes needs to access their prior instances in this
+    // phase if they are rewritten.
+    e->prepare_commit();
+  });
+
   // Transaction is now a go, set up in-memory cache state
   // invalidate now invalid blocks
   io_stat_t retire_stat;
@@ -1403,7 +1411,6 @@ record_t Cache::prepare_record(
 
     bufferlist bl;
     i->prepare_write();
-    i->prepare_commit();
     bl.append(i->get_bptr());
     if (is_root_type(i->get_type())) {
       ceph_assert(0 == "ROOT never gets written as a fresh block");
@@ -1457,7 +1464,6 @@ record_t Cache::prepare_record(
     assert(!i->is_inline());
     get_by_ext(efforts.fresh_ool_by_ext,
                i->get_type()).increment(i->get_length());
-    i->prepare_commit();
     if (is_backref_mapped_type(i->get_type())) {
       laddr_t alloc_laddr;
       if (i->is_logical()) {