For block drivers that don't advertise FUA support, we already call bdrv_co_flush(), which considers BDRV_O_NO_FLUSH. However, drivers that do support FUA still see the FUA flag with BDRV_O_NO_FLUSH and get the associated performance penalty that cache.no-flush=on was supposed to avoid.
Clear FUA for write requests if BDRV_O_NO_FLUSH is set. Signed-off-by: Kevin Wolf <kw...@redhat.com> --- block/io.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/io.c b/block/io.c index d369b994df..1ba8d1aeea 100644 --- a/block/io.c +++ b/block/io.c @@ -1058,6 +1058,10 @@ bdrv_driver_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes, return -ENOMEDIUM; } + if (bs->open_flags & BDRV_O_NO_FLUSH) { + flags &= ~BDRV_REQ_FUA; + } + if ((flags & BDRV_REQ_FUA) && (~bs->supported_write_flags & BDRV_REQ_FUA)) { flags &= ~BDRV_REQ_FUA; -- 2.48.1