block, block-backend: write some hot coroutine wrappers by hand
The introduction of the graph lock is causing blk_get_geometry, a hot function
used in the I/O path, to create a coroutine. However, the only part that really
needs to run in coroutine context is the call to bdrv_co_refresh_total_sectors,
which in turn only happens in the rare case of host CD-ROM devices.
So, write by hand the three wrappers on the path from blk_co_get_geometry to
bdrv_co_refresh_total_sectors, so that the coroutine wrapper is only created
if bdrv_nb_sectors actually calls bdrv_refresh_total_sectors.
Reported-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230407153303.391121-9-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index e8e08ad..d79a52c 100644
--- a/block.c
+++ b/block.c
@@ -5859,6 +5859,28 @@
return bs->total_sectors;
}
+/*
+ * This wrapper is written by hand because this function is in the hot I/O path,
+ * via blk_get_geometry.
+ */
+int64_t coroutine_mixed_fn bdrv_nb_sectors(BlockDriverState *bs)
+{
+ BlockDriver *drv = bs->drv;
+ IO_CODE();
+
+ if (!drv)
+ return -ENOMEDIUM;
+
+ if (bs->bl.has_variable_length) {
+ int ret = bdrv_refresh_total_sectors(bs, bs->total_sectors);
+ if (ret < 0) {
+ return ret;
+ }
+ }
+
+ return bs->total_sectors;
+}
+
/**
* Return length in bytes on success, -errno on error.
* The length is always a multiple of BDRV_SECTOR_SIZE.
