Commit c1087f12 authored by Max Reitz's avatar Max Reitz Committed by Kevin Wolf
Browse files

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: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 094e3639

block.c

+12 −0
Original line number Diff line number Diff line
@@ -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,

include/block/block_int.h

+15 −0
Original line number Diff line number Diff line
@@ -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 */