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