On 16.10.19 13:13, Vladimir Sementsov-Ogievskiy wrote: > 14.10.2019 18:39, Max Reitz wrote: >> Sometimes it is useful to be able to add a node to the block graph that >> takes or unshare a certain set of permissions for debugging purposes. >> This patch adds this capability to blkdebug. >> >> (Note that you cannot make blkdebug release or share permissions that it >> needs to take or cannot share, because this might result in assertion >> failures in the block layer. But if the blkdebug node has no parents, >> it will not take any permissions and share everything by default, so you >> can then freely choose what permissions to take and share.) >> >> Signed-off-by: Max Reitz <[email protected]> >> --- >> qapi/block-core.json | 14 ++++++- >> block/blkdebug.c | 91 +++++++++++++++++++++++++++++++++++++++++++- >> 2 files changed, 103 insertions(+), 2 deletions(-) >> >> diff --git a/qapi/block-core.json b/qapi/block-core.json >> index f66553aac7..054ce651de 100644 >> --- a/qapi/block-core.json >> +++ b/qapi/block-core.json >> @@ -3453,6 +3453,16 @@ >> # >> # @set-state: array of state-change descriptions >> # >> +# @take-child-perms: Permissions to take on @image in addition to what >> +# is necessary anyway (which depends on how the >> +# blkdebug node is used). Defaults to none. >> +# (since 4.2) >> +# >> +# @unshare-child-perms: Permissions not to share on @image in addition >> +# to what cannot be shared anyway (which depends >> +# on how the blkdebug node is used). Defaults >> +# to none. (since 4.2) >> +# >> # Since: 2.9 >> ## >> { 'struct': 'BlockdevOptionsBlkdebug', >> @@ -3462,7 +3472,9 @@ >> '*opt-write-zero': 'int32', '*max-write-zero': 'int32', >> '*opt-discard': 'int32', '*max-discard': 'int32', >> '*inject-error': ['BlkdebugInjectErrorOptions'], >> - '*set-state': ['BlkdebugSetStateOptions'] } } >> + '*set-state': ['BlkdebugSetStateOptions'], >> + '*take-child-perms': ['BlockPermission'], >> + '*unshare-child-perms': ['BlockPermission'] } } >> >> ## >> # @BlockdevOptionsBlklogwrites: >> diff --git a/block/blkdebug.c b/block/blkdebug.c >> index 5ae96c52b0..6807c03065 100644 >> --- a/block/blkdebug.c >> +++ b/block/blkdebug.c >> @@ -28,10 +28,14 @@ >> #include "qemu/cutils.h" >> #include "qemu/config-file.h" >> #include "block/block_int.h" >> +#include "block/qdict.h" >> #include "qemu/module.h" >> #include "qemu/option.h" >> +#include "qapi/qapi-visit-block-core.h" >> #include "qapi/qmp/qdict.h" >> +#include "qapi/qmp/qlist.h" >> #include "qapi/qmp/qstring.h" >> +#include "qapi/qobject-input-visitor.h" >> #include "sysemu/qtest.h" >> >> typedef struct BDRVBlkdebugState { >> @@ -44,6 +48,9 @@ typedef struct BDRVBlkdebugState { >> uint64_t opt_discard; >> uint64_t max_discard; >> >> + uint64_t take_child_perms; >> + uint64_t unshare_child_perms; >> + >> /* For blkdebug_refresh_filename() */ >> char *config_file; >> >> @@ -344,6 +351,67 @@ static void blkdebug_parse_filename(const char >> *filename, QDict *options, >> qdict_put_str(options, "x-image", filename); >> } >> >> +static int blkdebug_parse_perm_list(uint64_t *dest, QDict *options, >> + const char *prefix, Error **errp) >> +{ >> + int ret = 0; >> + QDict *subqdict = NULL; >> + QObject *crumpled_subqdict = NULL; >> + Visitor *v = NULL; >> + BlockPermissionList *perm_list = NULL, *element; >> + Error *local_err = NULL; >> + >> + qdict_extract_subqdict(options, &subqdict, prefix); >> + if (!qdict_size(subqdict)) { > > > Hmm, you consider it as a success, so you mean default. Then, it's safer to > set *dest = 0 here.
“Safer” depends on the purpose of this function, and right now it’s
simply to set all fields that are given in the options; not to reset any
that aren’t.
I suppose there’s no harm in changing the purpose of the function, though.
>> + goto out;
>> + }
>> +
>> + crumpled_subqdict = qdict_crumple(subqdict, errp);
>> + if (!crumpled_subqdict) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> + v = qobject_input_visitor_new(crumpled_subqdict);
>> + visit_type_BlockPermissionList(v, NULL, &perm_list, &local_err);
>> + if (local_err) {
>> + error_propagate(errp, local_err);
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>
> I'd prefer explicitly set *dest = 0 here too.
>
>> + for (element = perm_list; element; element = element->next) {
>> + *dest |= UINT64_C(1) << element->value;
>
> Hmm, so, you rely on correct correspondence between generated BlockPermission
> enum
> and unnamed enum with BLK_PERM_* constants...
>
> I'm afraid it's unsafe, so, in xdbg_graph_add_edge() special mapping variable
> is
> used + QEMU_BUILD_BUG_ON on BLK_PERM_ALL.
>
> I think something like this should be done here.
I don’t really like it because I think it’s cool to have a 1-to-1
relationship between the BLK_PERM_* constants and what’s defined in
QAPI. I don’t quite like assuming there isn’t, because there’s no
reason why they wouldn’t correspond.
In fact, I’d rather define the BLK_PERM_* constants based on the QAPI
enum, but I don’t know whether we want to include the QAPI header into
block.h. ...Well, judging from a quick test it looks like the header is
included into it recursively anyway. So maybe I’ll do that instead.
Max
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