From c1087f12066a1ff34153dd10662c1a46a874087c Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Wed, 22 May 2019 19:03:46 +0200 Subject: [PATCH] block: Add bdrv_child_refresh_perms() If a block node uses bdrv_child_try_set_perm() to change the permission it takes on its child, the result may be very short-lived. If anything makes the block layer recalculate the permissions internally, it will invoke the node driver's .bdrv_child_perm() implementation. The permission/shared permissions masks that returns will then override the values previously passed to bdrv_child_try_set_perm(). If drivers want a child edge to have specific values for the permissions/shared permissions mask, it must return them in .bdrv_child_perm(). Consequentially, there is no need for them to pass the same values to bdrv_child_try_set_perm() then: It is better to have a function that invokes .bdrv_child_perm() and calls bdrv_child_try_set_perm() with the result. This patch adds such a function under the name of bdrv_child_refresh_perms(). Signed-off-by: Max Reitz Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block.c | 12 ++++++++++++ include/block/block_int.h | 15 +++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/block.c b/block.c index ceb2ea23c5..013369851b 100644 --- a/block.c +++ b/block.c @@ -2083,6 +2083,18 @@ int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared, return 0; } +int bdrv_child_refresh_perms(BlockDriverState *bs, BdrvChild *c, Error **errp) +{ + uint64_t parent_perms, parent_shared; + uint64_t perms, shared; + + bdrv_get_cumulative_perm(bs, &parent_perms, &parent_shared); + bdrv_child_perm(bs, c->bs, c, c->role, NULL, parent_perms, parent_shared, + &perms, &shared); + + return bdrv_child_try_set_perm(c, perms, shared, errp); +} + void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c, const BdrvChildRole *role, BlockReopenQueue *reopen_queue, diff --git a/include/block/block_int.h b/include/block/block_int.h index a498c2670b..d6415b53c1 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -1165,9 +1165,24 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs, void *opaque, Error **errp); void bdrv_root_unref_child(BdrvChild *child); +/** + * Sets a BdrvChild's permissions. Avoid if the parent is a BDS; use + * bdrv_child_refresh_perms() instead and make the parent's + * .bdrv_child_perm() implementation return the correct values. + */ int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared, Error **errp); +/** + * Calls bs->drv->bdrv_child_perm() and updates the child's permission + * masks with the result. + * Drivers should invoke this function whenever an event occurs that + * makes their .bdrv_child_perm() implementation return different + * values than before, but which will not result in the block layer + * automatically refreshing the permissions. + */ +int bdrv_child_refresh_perms(BlockDriverState *bs, BdrvChild *c, Error **errp); + /* Default implementation for BlockDriver.bdrv_child_perm() that can be used by * block filters: Forward CONSISTENT_READ, WRITE, WRITE_UNCHANGED and RESIZE to * all children */