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From: Lance Yang In-Reply-To: <20260430042834.80895-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 220B240006 X-Stat-Signature: ohykhpctsi6n1tfi7t11cyisa6inzwo5 X-Rspam-User: X-HE-Tag: 1777525094-142365 X-HE-Meta: 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 v69yjUFe HSXAnMTbm72At3H+RYeOQc7YmaaKzMxmI7VewkNt257tIMe0hgbffdlJYtSLpUjSAVePO7u+oRim8W1iw64dBO/Uu3ZHezCiaZZqxqdPrk4cebLbAIN8Mz3EvACP9etn0jCyCuZ3Vly0zSsbXWB/pGN31ARXBFiNb3gMJrmjF1ktOMSk3Nf5EPn9mS+Gqni+KyX8LoNrxzFU8sNXJTijnLj0NyGm3gZocdKuwXdui2XRZLndwXDLm7lCNmEwuAzZvx5zibHdrWOjY8YIIQLmJQiVBfdK83x6r3hRHbdSoMiAKcK4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/4/30 12:28, Lance Yang wrote: > > On Thu, Apr 30, 2026 at 12:11:20PM +0800, Bibo Mao wrote: >> when executing command "make check" with qemu software, there is >> error report like this: >> BUG: Bad rss-counter state mm:00000000972846bc type:MM_FILEPAGES val:-4096 Comm:bios-tables-tes Pid:27802 >> BUG: Bad rss-counter state mm:00000000752180c5 type:MM_FILEPAGES val:-2048 Comm:worker Pid:27815 >> BUG: Bad rss-counter state mm:000000009c2f6a61 type:MM_FILEPAGES val:-2048 Comm:qom-test Pid:27825 > > Good catch! > >> The problem is that when application exits, rss counter is calculated >> with huge_zero_pmd huge page, instead it should be skipped. > > Looks like the same problem[1] we discussed recently. > > [1] https://lore.kernel.org/linux-mm/74a75b59-2e13-3985-ee99-d5521f39df2a@google.com/ > >> Signed-off-by: Bibo Mao >> --- >> mm/huge_memory.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 970e077019b7..3cbea344d4a2 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2423,6 +2423,9 @@ static void zap_huge_pmd_folio(struct mm_struct *mm, struct vm_area_struct *vma, >> { >> const bool is_device_private = folio_is_device_private(folio); >> >> + if (is_huge_zero_pmd(pmdval)) >> + return; >> + > > The huge zero PMD should not be returned by vm_normal_page_pmd() or > vm_normal_folio_pmd() as a normal folio. If it reaches > zap_huge_pmd_folio(), we already made the wrong normal-vs-special > decision ... > > So I don't think we should special-case it in zap_huge_pmd_folio(). That > only avoids this RSS decrement :) > > Could you please check whether the fix[2] also fixes your QEMU test? In addition, like x86-32, 64-bit LoongArch selects ARCH_HAS_PTE_SPECIAL, but not ARCH_SUPPORTS_HUGE_PFNMAP. So CONFIG_ARCH_SUPPORTS_PMD_PFNMAP is not enabled, and pmd_special() falls back to the generic stub that always returns false. So I guess the fix should do the trick :) > [2] https://lore.kernel.org/linux-mm/ea1453a6-14c9-4334-ac7e-2758586393b2@kernel.org/ > > Thanks, Lance