Re: [PATCH 10/15] mm/hugetlb: count again if the reserve map shrank

[sashiko-bot@kernel.org]

> hugetlb_reserve_pages() asks region_chg() how many pages of the range are
> missing in the reserve map, charges the cgroup, the subpool and the pool
> for that many, and then lets region_add() fill the gaps.
> 
> It copes with region_add() adding less, because a concurrent fault added
> an entry in the meantime; however, it does not expect it to add more.
> 
> Since restore_reserve_on_error() can delete the entry of an allocation
> that failed later on, entries also disappear without the inode lock that
> mmap() holds. For a previously unreserved page, UFFDIO_COPY can do this
> when the source is not resident: it allocates a folio, which adds the
> entry, fails to copy with page faults disabled, and takes both back.
> memfd_alloc_folio() does it when it has made a reservation and gets no
> folio it may pin.
> 
> [ ... ]
> 
> Fixes: 846be08578ed ("mm/hugetlb: expand restore_reserve_on_error functionality")
> Cc: stable@kernel.org
> Reported-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261028-fixes_hugetlb-v1-0-a0a033db180f@kernel.org?part=10