[Qemu-devel] [PATCH v1 06/17] block: introduce bdrv_co_can_bypass_co

[Ming Lei]

This function is introduced to check if the current block
I/O can be allowed to run without coroutine for sake of
performance.

Signed-off-by: Ming Lei <address@hidden>
---
 block.c |   38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/block.c b/block.c
index ac184ef..2326dab 100644
--- a/block.c
+++ b/block.c
@@ -4718,6 +4718,44 @@ static void coroutine_fn bdrv_co_do_rw(void *opaque)
     qemu_bh_schedule(acb->bh);
 }
 
+static bool bdrv_rw_aligned(BlockDriverState *bs,
+                            int64_t offset,
+                            int bytes)
+{
+    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
+
+    if ((offset & (align - 1)) || ((offset + bytes) & (align - 1))) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
+static bool bdrv_co_can_bypass_co(BlockDriverState *bs,
+                                  int64_t sector_num,
+                                  int nb_sectors,
+                                  BdrvRequestFlags flags,
+                                  bool is_write)
+{
+    if (flags || bs->copy_on_read || bs->io_limits_enabled) {
+        return false;
+    }
+
+    /* unaligned read is safe */
+    if (!is_write) {
+        return true;
+    }
+
+    if (!bs->enable_write_cache ||
+        bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF ||
+        !QLIST_EMPTY(&bs->before_write_notifiers.notifiers)) {
+        return false;
+    } else {
+        return bdrv_rw_aligned(bs, sector_num << BDRV_SECTOR_BITS,
+                               nb_sectors << BDRV_SECTOR_BITS);
+    }
+}
+
 static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
                                                int64_t sector_num,
                                                QEMUIOVector *qiov,
-- 
1.7.9.5