From db788c896eb1378ebc1f20dcc4954616a7631919 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Tue, 7 Feb 2023 15:37:16 -0500 Subject: [PATCH 5/5] block: fix detect-zeroes= with BDRV_REQ_REGISTERED_BUF When a write request is converted into a write zeroes request by the detect-zeroes= feature, it is no longer associated with an I/O buffer. The BDRV_REQ_REGISTERED_BUF flag doesn't make sense without an I/O buffer and must be cleared because bdrv_co_do_pwrite_zeroes() fails with -EINVAL when it's set. Fiona Ebner bisected and diagnosed this QEMU 7.2 regression where writes containing zeroes to a blockdev with discard=unmap,detect-zeroes=unmap fail. Buglink: https://gitlab.com/qemu-project/qemu/-/issues/1404 Fixes: e8b6535533be ("block: add BDRV_REQ_REGISTERED_BUF request flag") Tested-by: Fiona Ebner Cc: qemu-stable@nongnu.org Reviewed-by: Eric Blake Reviewed-by: Hanna Czenczek Signed-off-by: Stefan Hajnoczi Message-Id: <20230207203719.242926-2-stefanha@redhat.com> (cherry picked from commit 3c5867156eb81c7c71611d078b2c5c2c863f884a) --- block/io.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/io.c b/block/io.c index b9424024f9..bbaa0d1b2d 100644 --- a/block/io.c +++ b/block/io.c @@ -2087,6 +2087,9 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) { flags |= BDRV_REQ_MAY_UNMAP; } + + /* Can't use optimization hint with bufferless zero write */ + flags &= ~BDRV_REQ_REGISTERED_BUF; } if (ret < 0) { -- 2.37.3