> On Sep 22, 2026, at 02:58, Dave Jiang <[email protected]> wrote:
>
>
>
> On 9/18/26 10:03 PM, Muchun Song wrote:
>>
>>
>>> On Sep 19, 2026, at 01:02, Dave Jiang <[email protected]> wrote:
>>>
>>>
>>>
>>> On 9/15/26 2:56 AM, Muchun Song wrote:
>>>> While working on the HugeTLB Vmemmap Optimization (HVO) generalization,
>>>> Sashiko reported that memmap_init_zone_device() could be asked to
>>>> initialize struct pages with a large-page order for a physical range
>>>> that was not naturally aligned to that order.
>>>>
>>>> Following the Device DAX call path confirmed that the condition was
>>>> reachable. Device DAX range validation checks the range size, but not
>>>> its start address. An unaligned range can therefore reach
>>>> memmap_init_zone_device() after the device binds, and a subsequent write
>>>> to a userspace mapping may trigger a kernel panic. With the help of an
>>>> LLM, I was able to reproduce the failure.
>>>>
>>>> The automatic resize path has a related problem. It can split an aligned
>>>> size request across arbitrary free gaps, consume an unaligned fragment,
>>>> and leave the resize partially applied when a later allocation fails.
>>>>
>>>> This series validates both the start and size of every Device DAX range
>>>> and makes automatic resize account only for usable aligned space. It
>>>> also fixes the mapping sysfs attribute to propagate validation failures
>>>> instead of reporting success without allocating the requested range.
>>>>
>>>> Muchun Song (2):
>>>> dax/bus: fix Device DAX range alignment validation
>>>> dax/bus: fix mapping attribute error reporting
>>>>
>>>> drivers/dax/bus.c | 144 +++++++++++++++++++++++++++++++++++-----------
>>>> 1 file changed, 109 insertions(+), 35 deletions(-)
>>>>
>>>>
>>>> base-commit: 1a1de54f7369cd2b5bac0f265910e60ad3a6b4c3
>>>
>>> This commit does not exist in Linus's tree. Can you please base the series
>>> on top of the latest 7.3-rc tag so sashiko can look over it? Thanks!
>>
>> Hi,
>>
>> The series is based on linux-next 20260914, and drivers/dax/bus.c is
>> identical
>> between that branch and the latest 7.3-rc. Sashiko has also already reviewed
>> it
>> here: [1].
>>
>> Therefore, I didn't quite catch your point. Are you expecting Sashiko to
>> conduct
>> another round of review based on the 7.3-rc code? (Are you concerned about
>> issues
>> introduced by the additional commits in linux-next compared to 7.3-rc?)
>
> Ok that's fine. But next time please use a tag that's valid from Linus tree
> and not linux-next. While there's a sashiko link, I'd like to see the sashiko
> response on the mailing list for easier review. I'm not sure if it's due to
> the base commit or something else for it to not show up. Sometimes sashiko
> responds with no regression found and sometimes it just does not respond. I'm
> not sure why the varied behavior.
I previously worked based on the mm development model, and this is my
first time learning about the development rules for DAX. I will develop
DAX based on Linus's tree going forward.
Thanks,
Muchun
>
> DJ
>
>
>>
>> [1]
>> https://sashiko.dev/#/patchset/20260915095621.3744167-1-songmuchun%40bytedance.com
>>
>> Thanks,
>> Muchun
