Re: [PATCH v2 27/47] mm/mmu_gather: fix flushing ranges with 4 GiB or larger

[SJ Park]

On Thu, 29 Oct 2026 21:33:22 +0100 "David Hildenbrand (Arm)" <david@xxxxxxxxxx> wrote:

> From: Josef Bacik <josef@xxxxxxxxxxxxxx>
> 
> __tlb_adjust_range() takes the size of the range which has to be flushed
> as an unsigned int. Its callers, tlb_flush_{pte,pmd,pud,p4d}_range(), get
> and pass an unsigned long. Consequently, a range that is 4 GiB or larger
> gets truncated, possibly to 0.
> 
> On arm64 with hugetlb, a 64k kernel can have 16 GiB hugetlb folios
> mapped contiguously at the PMD level and flush them when unmapping, and a
> 16k kernel can flush 64 GiB PUDs through tlb_unshare_pmd_ptdesc(). So
> at least these two scenarios are affected.
> 
> Fix it by flushing the proper range instead of the truncated one by
> properly using "unsigned long" for range_size.

Makes sense to me.

> 
> Fix generated by an LLM and sent by Josef Bacik in private.
> 
> Fixes: b528e4b6405b ("mm/hugetlb: add tlb_remove_hugetlb_entry for handling hugetlb pages")
> Fixes: 8ce720d5bd91 ("mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Acked-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> [ david: use two-tab indent, simplify description ]

It seems the convention [1] is to put the above modification note right before
the last S-o-b: of David.  Maybe you forgot moving it after adding R-b: and
T-b: from great reviewers?

> Reviewed-by: Qi Zheng <qi.zheng@xxxxxxxxx>
> Reviewed-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> Tested-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> Reviewed-by: Dev Jain <dev.jain@xxxxxxx>
> Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
> Reviewed-by: Pedro Falcato <pfalcato@xxxxxxx>
> Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

Reviewed-by: SJ Park <sj@xxxxxxxxxx>

[1] https://docs.kernel.org/maintainer/modifying-patches.html


Thanks,
SJ

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