os/bluestore/BlueStore: do WAL ops buffered to avoid RMW issues

We may have multiple WAL ops that do read/modify/write covering
the same blocks.  To avoid the complexity of identifying those
situations and ensuring that we, say, wait for writes to complete
before reading them back again, just make the IO buffered and let
the page cache handle that for us.

This fixes the failure of LibRadosAio.RoundTripWriteFull.

Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index e3e2467bc0435372fd36133c593b7149e6b3107e..4e43425a439c2b3539896e6468601fb7e5f32188 100644 (file)
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -3433,6 +3433,9 @@ int BlueStore::_do_wal_op(bluestore_wal_op_t& wo, IOContext *ioc)
   // read all the overlay data first for apply
   _do_read_all_overlays(wo);
 
+  // NOTE: we are doing all reads and writes buffered so that we can
+  // avoid worrying about multiple RMW cycles over the same blocks.
+
   switch (wo.op) {
   case bluestore_wal_op_t::OP_WRITE:
   {
@@ -3469,7 +3472,7 @@ int BlueStore::_do_wal_op(bluestore_wal_op_t& wo, IOContext *ioc)
       bl.claim_append(t);
     }
     assert((bl.length() & ~block_mask) == 0);
-    bdev->aio_write(offset, bl, ioc, false);
+    bdev->aio_write(offset, bl, ioc, true);
   }
   break;
 
@@ -3487,7 +3490,7 @@ int BlueStore::_do_wal_op(bluestore_wal_op_t& wo, IOContext *ioc)
       bdev->read(first_offset, block_size, &first, ioc, true);
       size_t z_len = MIN(block_size - first_len, length);
       memset(first.c_str() + first_len, 0, z_len);
-      bdev->aio_write(first_offset, first, ioc, false);
+      bdev->aio_write(first_offset, first, ioc, true);
       offset += block_size - first_len;
       length -= z_len;
     }
@@ -3507,7 +3510,7 @@ int BlueStore::_do_wal_op(bluestore_wal_op_t& wo, IOContext *ioc)
               << offset << "~" << block_size << dendl;
       bdev->read(offset, block_size, &last, ioc, true);
       memset(last.c_str(), 0, length);
-      bdev->aio_write(offset, last, ioc, false);
+      bdev->aio_write(offset, last, ioc, true);
     }
   }
   break;