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block: Pull out bdrv_default_perms_for_cow() 

Right now, bdrv_format_default_perms() is used by format parents
(generally). We want to switch to a model where most parents use a
single BdrvChildClass, which then decides the permissions based on the
child role. To do so, we have to split bdrv_format_default_perms() into
separate functions for each such role.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200513110544.176672-17-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2020-05-13 13:05:26 +02:00 committed by Kevin Wolf
parent 33f2663bd5
commit 70082db4ef
1 changed files with 40 additions and 22 deletions
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62
block.c
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@ -2468,6 +2468,44 @@ void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c,
*nshared = (shared & DEFAULT_PERM_PASSTHROUGH) | DEFAULT_PERM_UNCHANGED;
}
static void bdrv_default_perms_for_cow(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_backing ||
(child_class == &child_of_bds && (role & BDRV_CHILD_COW)));
/*
* 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;
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,
@ -2505,28 +2543,8 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
*nperm = perm;
*nshared = shared;
} 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;
if (bs->open_flags & BDRV_O_INACTIVE) {
shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
}
*nperm = perm;
*nshared = shared;
bdrv_default_perms_for_cow(bs, c, child_class, role, reopen_queue,
perm, shared, nperm, nshared);
}
}