From: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
Signed-off-by: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
---
block.c | 22 ++++++++++++++++++++++
1 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/block.c b/block.c
index 1fbf4dd..6de6f89 100644
--- a/block.c
+++ b/block.c
@@ -1477,6 +1477,17 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t
sector_num, uint8_t *buf,
qemu_iovec_init_external(&qiov, &iov, 1);
+ /**
+ * In sync call context, when the vcpu is blocked, this throttling timer
+ * will not fire; so the I/O throttling function has to be disabled here
+ * if it has been enabled.
+ */
+ if (bs->io_limits_enabled) {
+ fprintf(stderr, "Disabling I/O throttling on '%s' due "
+ "to synchronous I/O.\n", bdrv_get_device_name(bs));
+ bdrv_io_limits_disable(bs);
+ }
+
if (qemu_in_coroutine()) {
/* Fast-path if already in coroutine context */
bdrv_rw_co_entry(&rwco);
@@ -1983,10 +1994,21 @@ static int guess_disk_lchs(BlockDriverState *bs,
struct partition *p;
uint32_t nr_sects;
uint64_t nb_sectors;
+ bool enabled;
bdrv_get_geometry(bs, &nb_sectors);
+ /**
+ * The function will be invoked during startup not only in sync I/O mode,
+ * but also in async I/O mode. So the I/O throttling function has to
+ * be disabled temporarily here, not permanently.
+ * When all sync I/O drivers are converted to async I/O, it will be
restored
+ * to the original state.
+ */
+ enabled = bs->io_limits_enabled;
+ bs->io_limits_enabled = false;
ret = bdrv_read(bs, 0, buf, 1);
+ bs->io_limits_enabled = enabled;
if (ret < 0)
return -1;
/* test msdos magic */
--
1.7.6
