diff options
Diffstat (limited to 'block.c')
| -rw-r--r-- | block.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/block.c b/block.c index 064e9d77fa..d67819f2a2 100644 --- a/block.c +++ b/block.c @@ -1560,6 +1560,50 @@ void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c, (c->shared_perm & DEFAULT_PERM_UNCHANGED); } +void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, + const BdrvChildRole *role, + uint64_t perm, uint64_t shared, + uint64_t *nperm, uint64_t *nshared) +{ + bool backing = (role == &child_backing); + assert(role == &child_backing || role == &child_file); + + if (!backing) { + /* Apart from the modifications below, the same permissions are + * forwarded and left alone as for filters */ + bdrv_filter_default_perms(bs, c, role, perm, shared, &perm, &shared); + + /* Format drivers may touch metadata even if the guest doesn't write */ + if (!bdrv_is_read_only(bs)) { + perm |= BLK_PERM_WRITE | BLK_PERM_RESIZE; + } + + /* bs->file always needs to be consistent because of the metadata. We + * can never allow other users to resize or write to it. */ + perm |= BLK_PERM_CONSISTENT_READ; + shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); + } else { + /* We want consistent read from backing files if the parent needs it. + * No other operations are performed on backing files. */ + perm &= BLK_PERM_CONSISTENT_READ; + + /* If the parent can deal with changing data, we're okay with a + * writable and resizable backing file. */ + /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */ + if (shared & BLK_PERM_WRITE) { + shared = BLK_PERM_WRITE | BLK_PERM_RESIZE; + } else { + shared = 0; + } + + shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD | + BLK_PERM_WRITE_UNCHANGED; + } + + *nperm = perm; + *nshared = shared; +} + static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs, bool check_new_perm) { |