From baa218a4170b17e3699272a481ee04616c9432f0 Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Mon, 4 Feb 2019 21:08:22 +0100
Subject: [PATCH 8/8] luks: Allow share-rw=on
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RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <20190204210822.10343-2-mreitz@redhat.com>
Patchwork-id: 84228
O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 1/1] luks: Allow share-rw=on
Bugzilla: 1598119
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Yash Mankad <ymankad@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

From: Fam Zheng <famz@redhat.com>

Format drivers such as qcow2 don't allow sharing the same image between
two QEMU instances in order to prevent image corruptions, because of
metadata cache. LUKS driver don't modify metadata except for when
creating image, so it is safe to relax the permission. This makes
share-rw=on property work on virtual devices.

Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 497da8236ab2663a8108858ba7ea59aac21c5fe6)
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/crypto.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/crypto.c b/block/crypto.c
index 02f04f3..0bb0db6 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -698,7 +698,9 @@ BlockDriver bdrv_crypto_luks = {
     .bdrv_probe         = block_crypto_probe_luks,
     .bdrv_open          = block_crypto_open_luks,
     .bdrv_close         = block_crypto_close,
-    .bdrv_child_perm    = bdrv_format_default_perms,
+    /* This driver doesn't modify LUKS metadata except when creating image.
+     * Allow share-rw=on as a special case. */
+    .bdrv_child_perm    = bdrv_filter_default_perms,
     .bdrv_co_create     = block_crypto_co_create_luks,
     .bdrv_co_create_opts = block_crypto_co_create_opts_luks,
     .bdrv_co_truncate   = block_crypto_co_truncate,
-- 
1.8.3.1