[v4,4/5] block: add flush callback

Commit Message

Pavel Dovgalyuk March 10, 2016, 11:56 a.m. UTC

This patch adds callback for flush request. This callback is responsible
for flushing whole block devices stack. bdrv_flush function does not
proceed to underlying devices. It should be performed by this callback
function, if needed.

Signed-off-by: Pavel Dovgalyuk <[e-mail]>
---
 block/io.c                |    7 +++++++
 include/block/block_int.h |    7 +++++++
 2 files changed, 14 insertions(+), 0 deletions(-)

Patch

diff --git a/block/io.c b/block/io.c
index a69bfc4..242ee0c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2369,6 +2369,13 @@  int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
     }
 
     tracked_request_begin(&req, bs, 0, 0, BDRV_TRACKED_FLUSH);
+
+    /* Write back all layers by calling one driver function */
+    if (bs->drv->bdrv_co_flush) {
+        ret = bs->drv->bdrv_co_flush(bs);
+        goto out;
+    }
+
     /* Write back cached data to the OS even with cache=unsafe */
     BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_OS);
     if (bs->drv->bdrv_co_flush_to_os) {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 9ef823a..8f72037 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -176,6 +176,13 @@  struct BlockDriver {
     int (*bdrv_inactivate)(BlockDriverState *bs);
 
     /*
+     * Flushes all data for all layers by calling bdrv_co_flush for underlying
+     * layers, if needed. This function is needed for deterministic
+     * synchronization of the flush finishing callback.
+     */
+    int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs);
+
+    /*
      * Flushes all data that was already written to the OS all the way down to
      * the disk (for example raw-posix calls fsync()).
      */