From 1c4c0df8838e32c524c86ae7ab0fcdc56cb0cad0 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Mon, 4 Dec 2017 12:10:00 +0100
Subject: [PATCH 29/36] qemu-io: Drop write permissions before read-only reopen

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20171204121007.12964-2-kwolf@redhat.com>
Patchwork-id: 78106
O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH v2 1/8] qemu-io: Drop write permissions before read-only reopen
Bugzilla: 1492178
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

qemu-io provides a 'reopen' command that allows switching from writable
to read-only access. We need to make sure that we don't try to keep
write permissions to a BlockBackend that becomes read-only, otherwise
things are going to fail.

This requires a bdrv_drain() call because otherwise in-flight AIO
write requests could issue new internal requests while the permission
has already gone away, which would cause assertion failures. Draining
the queue doesn't break AIO requests in any new way, bdrv_reopen() would
drain it anyway only a few lines later.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
(cherry picked from commit f3adefb2cea1c63b7b198acaef5e40eb4b2d2d39)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 qemu-io-cmds.c             | 12 ++++++++++++
 tests/qemu-iotests/187.out |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 2811a89..3727fb4 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -2010,6 +2010,18 @@ static int reopen_f(BlockBackend *blk, int argc, char **argv)
         return 0;
     }
 
+    if (!(flags & BDRV_O_RDWR)) {
+        uint64_t orig_perm, orig_shared_perm;
+
+        bdrv_drain(bs);
+
+        blk_get_perm(blk, &orig_perm, &orig_shared_perm);
+        blk_set_perm(blk,
+                     orig_perm & ~(BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED),
+                     orig_shared_perm,
+                     &error_abort);
+    }
+
     qopts = qemu_opts_find(&reopen_opts, NULL);
     opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : NULL;
     qemu_opts_reset(&reopen_opts);
diff --git a/tests/qemu-iotests/187.out b/tests/qemu-iotests/187.out
index 68fb944..30b987f 100644
--- a/tests/qemu-iotests/187.out
+++ b/tests/qemu-iotests/187.out
@@ -12,7 +12,7 @@ Start from read-write
 
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-write failed: Operation not permitted
+Block node is read-only
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 *** done
-- 
1.8.3.1