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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Jul 05, 2025 at 10:14:18AM +1000, Balbir Singh wrote: > On 7/4/25 21:10, Mika Penttilä wrote: > >> /* Racy check whether the huge page can be split */ > >> @@ -3543,6 +3594,10 @@ static int __split_unmapped_folio(struct folio *folio, int new_order, > >> ((mapping || swap_cache) ? > >> folio_nr_pages(release) : 0)); > >> > >> + if (folio_is_device_private(release)) > >> + percpu_ref_get_many(&release->pgmap->ref, > >> + (1 << new_order) - 1); > > > > pgmap refcount should not be modified here, count should remain the same after the split also Agreed. > > > > > > Good point, let me revisit the accounting Yes, hopefully we can just delete it. > For this patch series, the tests did not catch it since new ref's evaluate to 0 You may not notice bad accounting here unless you unload the kernel module, which can hang during memunmap() pages waiting for the refcount to go to zero. > Thanks, > Balbir Singh