[PATCH v2 17/33] block: Split bdrv_default_perms_for_storage()

[Max Reitz <mreitz@redhat.com>]

We can be less restrictive about pure data children than those with
metadata on them.

For bdrv_format_default_perms(), we keep the safe option of
bdrv_default_perms_for_metadata() (until we drop
bdrv_format_default_perms() altogether).

That means that bdrv_default_perms_for_data() is unused at this point.
We will use it for all children that have the DATA role, but not the
METADATA role.  So far, no child has any role, so we do not use it, but
that will change.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 10 deletions(-)

diff --git a/block.c b/block.c
index b7999696d4..3619756175 100644
--- a/block.c
+++ b/block.c
@@ -2318,18 +2318,17 @@ static void bdrv_default_perms_for_backing(BlockDriverState *bs, BdrvChild *c,
     *nshared = shared;
 }
 
-static void bdrv_default_perms_for_storage(BlockDriverState *bs, BdrvChild *c,
-                                           const BdrvChildClass *child_class,
-                                           BdrvChildRole role,
-                                           BlockReopenQueue *reopen_queue,
-                                           uint64_t perm, uint64_t shared,
-                                           uint64_t *nperm, uint64_t *nshared)
+static void bdrv_default_perms_for_metadata(BlockDriverState *bs, BdrvChild *c,
+                                            const BdrvChildClass *child_class,
+                                            BdrvChildRole role,
+                                            BlockReopenQueue *reopen_queue,
+                                            uint64_t perm, uint64_t shared,
+                                            uint64_t *nperm, uint64_t *nshared)
 {
     int flags;
 
     assert(child_class == &child_file ||
-           (child_class == &child_of_bds &&
-            (role & (BDRV_CHILD_METADATA | BDRV_CHILD_DATA))));
+           (child_class == &child_of_bds && (role & BDRV_CHILD_METADATA)));
 
     flags = bdrv_reopen_get_flags(reopen_queue, bs);
 
@@ -2362,6 +2361,40 @@ static void bdrv_default_perms_for_storage(BlockDriverState *bs, BdrvChild *c,
     *nshared = shared;
 }
 
+/* TODO: Use */
+static void __attribute__((unused))
+bdrv_default_perms_for_data(BlockDriverState *bs, BdrvChild *c,
+                            const BdrvChildClass *child_class,
+                            BdrvChildRole role,
+                            BlockReopenQueue *reopen_queue,
+                            uint64_t perm, uint64_t shared,
+                            uint64_t *nperm, uint64_t *nshared)
+{
+    assert(child_class == &child_of_bds && (role & BDRV_CHILD_DATA));
+
+    /*
+     * Apart from the modifications below, the same permissions are
+     * forwarded and left alone as for filters
+     */
+    bdrv_filter_default_perms(bs, c, child_class, role, reopen_queue,
+                              perm, shared, &perm, &shared);
+
+    /*
+     * We cannot allow other users to resize the file because the
+     * format driver might have some assumptions about the size
+     * (e.g. because it is stored in metadata, or because the file is
+     * split into fixed-size data files).
+     */
+    shared &= ~BLK_PERM_RESIZE;
+
+    if (bs->open_flags & BDRV_O_INACTIVE) {
+        shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
+    }
+
+    *nperm = perm;
+    *nshared = shared;
+}
+
 void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
                                const BdrvChildClass *child_class,
                                BdrvChildRole role,
@@ -2373,8 +2406,8 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
     assert(child_class == &child_backing || child_class == &child_file);
 
     if (!backing) {
-        bdrv_default_perms_for_storage(bs, c, child_class, role, reopen_queue,
-                                       perm, shared, nperm, nshared);
+        bdrv_default_perms_for_metadata(bs, c, child_class, role, reopen_queue,
+                                        perm, shared, nperm, nshared);
     } else {
         bdrv_default_perms_for_backing(bs, c, child_class, role, reopen_queue,
                                        perm, shared, nperm, nshared);
-- 
2.24.1