Re: [PATCH v2 05/36] block: add bdrv_parent_try_set_aio_context - Vladimir Sementsov-Ogievskiy

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org, armbru@redhat.com, qemu-devel@nongnu.org,
	mreitz@redhat.com, den@openvz.org, jsnow@redhat.com
Subject: Re: [PATCH v2 05/36] block: add bdrv_parent_try_set_aio_context
Date: Mon, 18 Jan 2021 20:26:10 +0300	[thread overview]
Message-ID: <61df94ea-31eb-4e5b-d1d8-1efcc4a3a636@virtuozzo.com> (raw)
In-Reply-To: <20210118150819.GF11555@merkur.fritz.box>

18.01.2021 18:08, Kevin Wolf wrote:
> Am 27.11.2020 um 15:44 hat Vladimir Sementsov-Ogievskiy geschrieben:
>> We already have bdrv_parent_can_set_aio_context(). Add corresponding
>> bdrv_parent_set_aio_context_ignore() and
>> bdrv_parent_try_set_aio_context() and use them instead of open-coding.
>>
>> Make bdrv_parent_try_set_aio_context() public, as it will be used in
>> further commit.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   include/block/block.h |  2 ++
>>   block.c               | 51 +++++++++++++++++++++++++++++++++----------
>>   2 files changed, 41 insertions(+), 12 deletions(-)
>>
>> diff --git a/include/block/block.h b/include/block/block.h
>> index ee3f5a6cca..550c5a7513 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -686,6 +686,8 @@ bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
>>                                       GSList **ignore, Error **errp);
>>   bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx,
>>                                 GSList **ignore, Error **errp);
>> +int bdrv_parent_try_set_aio_context(BdrvChild *c, AioContext *ctx,
>> +                                    Error **errp);
>>   int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz);
>>   int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
>>   
>> diff --git a/block.c b/block.c
>> index 916087ee1a..5d925c208d 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -81,6 +81,9 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
>>                                              BdrvChildRole child_role,
>>                                              Error **errp);
>>   
>> +static void bdrv_parent_set_aio_context_ignore(BdrvChild *c, AioContext *ctx,
>> +                                               GSList **ignore);
>> +
>>   /* If non-zero, use only whitelisted block drivers */
>>   static int use_bdrv_whitelist;
>>   
>> @@ -2655,17 +2658,12 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
>>        * try moving the parent into the AioContext of child_bs instead. */
>>       if (bdrv_get_aio_context(child_bs) != ctx) {
>>           ret = bdrv_try_set_aio_context(child_bs, ctx, &local_err);
>> -        if (ret < 0 && child_class->can_set_aio_ctx) {
>> -            GSList *ignore = g_slist_prepend(NULL, child);
>> -            ctx = bdrv_get_aio_context(child_bs);
> 
> You are losing this line...
> 
>> -            if (child_class->can_set_aio_ctx(child, ctx, &ignore, NULL)) {
>> -                error_free(local_err);
>> +        if (ret < 0) {
>> +            if (bdrv_parent_try_set_aio_context(child, ctx, NULL) == 0) {
> 
> ...before this one, so I think the wrong context is passed now. Instead
> of trying to move the parent to the AioContext of the child, we'll try
> to move it to the AioContext in which it already is (and which doesn't
> match the AioContext of the child).
> 

Oops, right, will fix

> 
>>                   ret = 0;
>> -                g_slist_free(ignore);
>> -                ignore = g_slist_prepend(NULL, child);
>> -                child_class->set_aio_ctx(child, ctx, &ignore);
>> +                error_free(local_err);
>> +                local_err = NULL;
>>               }
>> -            g_slist_free(ignore);
>>           }
>>           if (ret < 0) {
>>               error_propagate(errp, local_err);
>> @@ -6452,9 +6450,7 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
>>           if (g_slist_find(*ignore, child)) {
>>               continue;
>>           }
>> -        assert(child->klass->set_aio_ctx);
>> -        *ignore = g_slist_prepend(*ignore, child);
>> -        child->klass->set_aio_ctx(child, new_context, ignore);
>> +        bdrv_parent_set_aio_context_ignore(child, new_context, ignore);
>>       }
>>   
>>       bdrv_detach_aio_context(bs);
>> @@ -6511,6 +6507,37 @@ static bool bdrv_parent_can_set_aio_context(BdrvChild *c, AioContext *ctx,
>>       return true;
>>   }
>>   
>> +static void bdrv_parent_set_aio_context_ignore(BdrvChild *c, AioContext *ctx,
>> +                                               GSList **ignore)
>> +{
>> +    if (g_slist_find(*ignore, c)) {
>> +        return;
>> +    }
>> +    *ignore = g_slist_prepend(*ignore, c);
>> +
>> +    assert(c->klass->set_aio_ctx);
>> +    c->klass->set_aio_ctx(c, ctx, ignore);
>> +}
>> +
>> +int bdrv_parent_try_set_aio_context(BdrvChild *c, AioContext *ctx,
>> +                                    Error **errp)
>> +{
>> +    GSList *ignore = NULL;
>> +
>> +    if (!bdrv_parent_can_set_aio_context(c, ctx, &ignore, errp)) {
>> +        g_slist_free(ignore);
>> +        return -EPERM;
>> +    }
>> +
>> +    g_slist_free(ignore);
>> +    ignore = NULL;
>> +
>> +    bdrv_parent_set_aio_context_ignore(c, ctx, &ignore);
>> +    g_slist_free(ignore);
>> +
>> +    return 0;
>> +}
>> +
>>   bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
>>                                       GSList **ignore, Error **errp)
>>   {
>> -- 
>> 2.21.3
>>
> 


-- 
Best regards,
Vladimir