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block: Add *tighten_restrictions to *check*_perm() 

This patch makes three functions report whether the necessary permission
change tightens restrictions or not.  These functions are:
- bdrv_check_perm()
- bdrv_check_update_perm()
- bdrv_child_check_perm()

Callers can use this result to decide whether a failure is fatal or not
(see the next patch).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2019-05-22 19:03:50 +02:00 committed by Kevin Wolf
parent 87ace5f8b6
commit 9eab154415
1 changed files with 70 additions and 17 deletions
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87
block.c
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@ -1706,7 +1706,8 @@ static int bdrv_fill_options(QDict **options, const char *filename,
static int bdrv_child_check_perm(BdrvChild *c, BlockReopenQueue *q,
uint64_t perm, uint64_t shared,
GSList *ignore_children, Error **errp);
GSList *ignore_children,
bool *tighten_restrictions, Error **errp);
static void bdrv_child_abort_perm_update(BdrvChild *c);
static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared);
static void bdrv_get_cumulative_perm(BlockDriverState *bs, uint64_t *perm,
@ -1781,18 +1782,43 @@ static void bdrv_child_perm(BlockDriverState *bs, BlockDriverState *child_bs,
* permissions of all its parents. This involves checking whether all necessary
* permission changes to child nodes can be performed.
*
* Will set *tighten_restrictions to true if and only if new permissions have to
* be taken or currently shared permissions are to be unshared. Otherwise,
* errors are not fatal as long as the caller accepts that the restrictions
* remain tighter than they need to be. The caller still has to abort the
* transaction.
* @tighten_restrictions cannot be used together with @q: When reopening, we may
* encounter fatal errors even though no restrictions are to be tightened. For
* example, changing a node from RW to RO will fail if the WRITE permission is
* to be kept.
*
* A call to this function must always be followed by a call to bdrv_set_perm()
* or bdrv_abort_perm_update().
*/
static int bdrv_check_perm(BlockDriverState *bs, BlockReopenQueue *q,
uint64_t cumulative_perms,
uint64_t cumulative_shared_perms,
GSList *ignore_children, Error **errp)
GSList *ignore_children,
bool *tighten_restrictions, Error **errp)
{
BlockDriver *drv = bs->drv;
BdrvChild *c;
int ret;
assert(!q || !tighten_restrictions);
if (tighten_restrictions) {
uint64_t current_perms, current_shared;
uint64_t added_perms, removed_shared_perms;
bdrv_get_cumulative_perm(bs, &current_perms, &current_shared);
added_perms = cumulative_perms & ~current_perms;
removed_shared_perms = current_shared & ~cumulative_shared_perms;
*tighten_restrictions = added_perms || removed_shared_perms;
}
/* Write permissions never work with read-only images */
if ((cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) &&
!bdrv_is_writable_after_reopen(bs, q))
@ -1833,11 +1859,18 @@ static int bdrv_check_perm(BlockDriverState *bs, BlockReopenQueue *q,
/* Check all children */
QLIST_FOREACH(c, &bs->children, next) {
uint64_t cur_perm, cur_shared;
bool child_tighten_restr;
bdrv_child_perm(bs, c->bs, c, c->role, q,
cumulative_perms, cumulative_shared_perms,
&cur_perm, &cur_shared);
ret = bdrv_child_check_perm(c, q, cur_perm, cur_shared,
ignore_children, errp);
ret = bdrv_child_check_perm(c, q, cur_perm, cur_shared, ignore_children,
tighten_restrictions ? &child_tighten_restr
: NULL,
errp);
if (tighten_restrictions) {
*tighten_restrictions |= child_tighten_restr;
}
if (ret < 0) {
return ret;
}
@ -1961,17 +1994,23 @@ char *bdrv_perm_names(uint64_t perm)
* set, the BdrvChild objects in this list are ignored in the calculations;
* this allows checking permission updates for an existing reference.
*
* See bdrv_check_perm() for the semantics of @tighten_restrictions.
*
* Needs to be followed by a call to either bdrv_set_perm() or
* bdrv_abort_perm_update(). */
static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q,
uint64_t new_used_perm,
uint64_t new_shared_perm,
GSList *ignore_children, Error **errp)
GSList *ignore_children,
bool *tighten_restrictions,
Error **errp)
{
BdrvChild *c;
uint64_t cumulative_perms = new_used_perm;
uint64_t cumulative_shared_perms = new_shared_perm;
assert(!q || !tighten_restrictions);
/* There is no reason why anyone couldn't tolerate write_unchanged */
assert(new_shared_perm & BLK_PERM_WRITE_UNCHANGED);
@ -1983,6 +2022,11 @@ static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q,
if ((new_used_perm & c->shared_perm) != new_used_perm) {
char *user = bdrv_child_user_desc(c);
char *perm_names = bdrv_perm_names(new_used_perm & ~c->shared_perm);
if (tighten_restrictions) {
*tighten_restrictions = true;
}
error_setg(errp, "Conflicts with use by %s as '%s', which does not "
"allow '%s' on %s",
user, c->name, perm_names, bdrv_get_node_name(c->bs));
@ -1994,6 +2038,11 @@ static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q,
if ((c->perm & new_shared_perm) != c->perm) {
char *user = bdrv_child_user_desc(c);
char *perm_names = bdrv_perm_names(c->perm & ~new_shared_perm);
if (tighten_restrictions) {
*tighten_restrictions = true;
}
error_setg(errp, "Conflicts with use by %s as '%s', which uses "
"'%s' on %s",
user, c->name, perm_names, bdrv_get_node_name(c->bs));
@ -2007,19 +2056,21 @@ static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q,
}
return bdrv_check_perm(bs, q, cumulative_perms, cumulative_shared_perms,
ignore_children, errp);
ignore_children, tighten_restrictions, errp);
}
/* Needs to be followed by a call to either bdrv_child_set_perm() or
* bdrv_child_abort_perm_update(). */
static int bdrv_child_check_perm(BdrvChild *c, BlockReopenQueue *q,
uint64_t perm, uint64_t shared,
GSList *ignore_children, Error **errp)
GSList *ignore_children,
bool *tighten_restrictions, Error **errp)
{
int ret;
ignore_children = g_slist_prepend(g_slist_copy(ignore_children), c);
ret = bdrv_check_update_perm(c->bs, q, perm, shared, ignore_children, errp);
ret = bdrv_check_update_perm(c->bs, q, perm, shared, ignore_children,
tighten_restrictions, errp);
g_slist_free(ignore_children);
if (ret < 0) {
@ -2072,7 +2123,7 @@ int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared,
{
int ret;
ret = bdrv_child_check_perm(c, NULL, perm, shared, NULL, errp);
ret = bdrv_child_check_perm(c, NULL, perm, shared, NULL, NULL, errp);
if (ret < 0) {
bdrv_child_abort_perm_update(c);
return ret;
@ -2258,7 +2309,8 @@ static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs)
* because we're just taking a parent away, so we're loosening
* restrictions. */
bdrv_get_cumulative_perm(old_bs, &perm, &shared_perm);
bdrv_check_perm(old_bs, NULL, perm, shared_perm, NULL, &error_abort);
bdrv_check_perm(old_bs, NULL, perm, shared_perm, NULL,
NULL, &error_abort);
bdrv_set_perm(old_bs, perm, shared_perm);
/* When the parent requiring a non-default AioContext is removed, the
@ -2288,7 +2340,8 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
Error *local_err = NULL;
int ret;
ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, errp);
ret = bdrv_check_update_perm(child_bs, NULL, perm, shared_perm, NULL, NULL,
errp);
if (ret < 0) {
bdrv_abort_perm_update(child_bs);
bdrv_unref(child_bs);
@ -3369,7 +3422,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
BDRVReopenState *state = &bs_entry->state;
ret = bdrv_check_perm(state->bs, bs_queue, state->perm,
state->shared_perm, NULL, errp);
state->shared_perm, NULL, NULL, errp);
if (ret < 0) {
goto cleanup_perm;
}
@ -3381,7 +3434,7 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
state->perm, state->shared_perm,
&nperm, &nshared);
ret = bdrv_check_update_perm(state->new_backing_bs, NULL,
nperm, nshared, NULL, errp);
nperm, nshared, NULL, NULL, errp);
if (ret < 0) {
goto cleanup_perm;
}
@ -4097,7 +4150,7 @@ void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
/* Check whether the required permissions can be granted on @to, ignoring
* all BdrvChild in @list so that they can't block themselves. */
ret = bdrv_check_update_perm(to, NULL, perm, shared, list, errp);
ret = bdrv_check_update_perm(to, NULL, perm, shared, list, NULL, errp);
if (ret < 0) {
bdrv_abort_perm_update(to);
goto out;
@ -4444,7 +4497,7 @@ int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base,
/* Check whether we are allowed to switch c from top to base */
GSList *ignore_children = g_slist_prepend(NULL, c);
ret = bdrv_check_update_perm(base, NULL, c->perm, c->shared_perm,
ignore_children, &local_err);
ignore_children, NULL, &local_err);
g_slist_free(ignore_children);
if (ret < 0) {
error_report_err(local_err);
@ -5219,7 +5272,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs,
*/
bs->open_flags &= ~BDRV_O_INACTIVE;
bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, &local_err);
ret = bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, NULL, &local_err);
if (ret < 0) {
bs->open_flags |= BDRV_O_INACTIVE;
error_propagate(errp, local_err);
@ -5369,7 +5422,7 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs)
/* Update permissions, they may differ for inactive nodes */
bdrv_get_cumulative_perm(bs, &perm, &shared_perm);
bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, &error_abort);
bdrv_check_perm(bs, NULL, perm, shared_perm, NULL, NULL, &error_abort);
bdrv_set_perm(bs, perm, shared_perm);