Re: [PATCH 3/4] block: add IOC_PR_READ_KEYS ioctl

Stefan Hajnoczi
2025-12-01T18:36:34Z

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On Mon, Dec 01, 2025 at 05:26:27PM +0100, Krzysztof Kozlowski wrote:
> On 01/12/2025 16:06, Stefan Hajnoczi wrote:
> > On Sat, Nov 29, 2025 at 03:32:35PM +0100, Krzysztof Kozlowski wrote:
> >> On 27/11/2025 08:07, Hannes Reinecke wrote:
> >>>
> >>>> + size_t keys_info_len = struct_size(keys_info, keys, inout.num_keys);
> >>>> +
> >>>> + keys_info = kzalloc(keys_info_len, GFP_KERNEL);
> >>>> + if (!keys_info)
> >>>> + return -ENOMEM;
> >>>> +
> >>>> + keys_info->num_keys = inout.num_keys;
> >>>> +
> >>>> + ret = ops->pr_read_keys(bdev, keys_info);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + /* Copy out individual keys */
> >>>> + u64 __user *keys_ptr = u64_to_user_ptr(inout.keys_ptr);
> >>>> + u32 num_copy_keys = min(inout.num_keys, keys_info->num_keys);
> >>>> + size_t keys_copy_len = num_copy_keys * sizeof(keys_info->keys[0]);
> >>>
> >>> We just had the discussion about variable declarations on the ksummit
> >>> lists; I really would prefer to have all declarations at the start of
> >>> the scope (read: at the start of the function here).
> >>
> >> Then also cleanup.h should not be used here.
> >
> > Hi Krzysztof,
> > The documentation in cleanup.h says:
> >
> > * Given that the "__free(...) = NULL" pattern for variables defined at
> > * the top of the function poses this potential interdependency problem
> > * the recommendation is to always define and assign variables in one
> > ^^^^^^^^^^^^^^
> > * statement and not group variable definitions at the top of the
> > * function when __free() is used.
> >
> > This is a recommendation, not mandatory. It is also describing a
> > scenario that does not apply here.
>
> If you have actual argument, so allocation in some if branch, the of course.

I'm pointing out that the documentation uses the word "recommendation",
which is usually not considered mandatory but a suggestion.

Please update the documentation to clarify that __free() _must_ be
assigned the real value (no NULL initialization) so that it's clear this
is not a suggestion but mandatory.

Stefan

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