28.10.2019 13:46, Max Reitz wrote: > 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 <mre...@redhat.com> >>> --- >>> 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. >
If BLK_PERM_* are defined in manner making the correspondence obvious, that's OK, of course. -- Best regards, Vladimir