[Qemu-block] [PATCH 1/6] qemu-io: Reset qemuio_blk permissions before each command

[Kevin Wolf]

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.

command() already makes sure to request any additional permissions that
a qemu-io command requires, so just resetting the permissions to values
that are safe for read-only images is enough to fix this.

As a side effect, this makes the output of qemu-iotests case 187 more
consistent.

Signed-off-by: Kevin Wolf <address@hidden>
---
 qemu-io.c                  | 13 +++++++++++++
 tests/qemu-iotests/187.out |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/qemu-io.c b/qemu-io.c
index 265445ad89..9e031f0f8e 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -366,6 +366,12 @@ static void command_loop(void)
     char *input;
 
     for (i = 0; !done && i < ncmdline; i++) {
+        /* Make sure that we start each command with clean permissions and only
+         * add whatever the specific cmdinfo_t describes */
+        if (qemuio_blk) {
+            blk_set_perm(qemuio_blk, BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL,
+                         &error_abort);
+        }
         done = qemuio_command(qemuio_blk, cmdline[i]);
     }
     if (cmdline) {
@@ -391,6 +397,13 @@ static void command_loop(void)
         if (input == NULL) {
             break;
         }
+
+        /* Make sure that we start each command with clean permissions and only
+         * add whatever the specific cmdinfo_t describes */
+        if (qemuio_blk) {
+            blk_set_perm(qemuio_blk, BLK_PERM_CONSISTENT_READ, BLK_PERM_ALL,
+                         &error_abort);
+        }
         done = qemuio_command(qemuio_blk, input);
         g_free(input);
 
diff --git a/tests/qemu-iotests/187.out b/tests/qemu-iotests/187.out
index 68fb944cd5..30b987f71f 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
-- 
2.13.5