block: Add bdrv_qapi_perm_to_blk_perm()
We need some way to correlate QAPI BlockPermission values with
BLK_PERM_* flags. We could:
(1) have the same order in the QAPI definition as the the BLK_PERM_*
flags are in LSb-first order. However, then there is no guarantee
that they actually match (e.g. when someone modifies the QAPI schema
without thinking of the BLK_PERM_* definitions).
We could add static assertions, but these would break what’s good
about this solution, namely its simplicity.
(2) define the BLK_PERM_* flags based on the BlockPermission values.
But this way whenever someone were to modify the QAPI order
(perfectly sensible in theory), the BLK_PERM_* values would change.
Because these values are used for file locking, this might break
file locking between different qemu versions.
Therefore, go the slightly more cumbersome way: Add a function to
translate from the QAPI constants to the BLK_PERM_* flags.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20191108123455.39445-2-mreitz@redhat.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c
index 1b6f7c8..28eb5a7 100644
--- a/block.c
+++ b/block.c
@@ -2227,6 +2227,24 @@
*nshared = shared;
}
+uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm)
+{
+ static const uint64_t permissions[] = {
+ [BLOCK_PERMISSION_CONSISTENT_READ] = BLK_PERM_CONSISTENT_READ,
+ [BLOCK_PERMISSION_WRITE] = BLK_PERM_WRITE,
+ [BLOCK_PERMISSION_WRITE_UNCHANGED] = BLK_PERM_WRITE_UNCHANGED,
+ [BLOCK_PERMISSION_RESIZE] = BLK_PERM_RESIZE,
+ [BLOCK_PERMISSION_GRAPH_MOD] = BLK_PERM_GRAPH_MOD,
+ };
+
+ QEMU_BUILD_BUG_ON(ARRAY_SIZE(permissions) != BLOCK_PERMISSION__MAX);
+ QEMU_BUILD_BUG_ON(1UL << ARRAY_SIZE(permissions) != BLK_PERM_ALL + 1);
+
+ assert(qapi_perm < BLOCK_PERMISSION__MAX);
+
+ return permissions[qapi_perm];
+}
+
static void bdrv_replace_child_noperm(BdrvChild *child,
BlockDriverState *new_bs)
{
