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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4526e056138sm133067405e9.5.2025.06.10.00.08.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jun 2025 00:08:45 -0700 (PDT) Message-ID: <398d49f6-00c8-4bd8-ba30-62cbf0efee46@redhat.com> Date: Tue, 10 Jun 2025 09:08:44 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] mm: use folio_expected_ref_count() helper for reference counting To: Shivank Garg , mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-mm@kvack.org References: <20250609170806.447302-2-shivankg@amd.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 09.06.25 19:08, Shivank Garg wrote: > Replace open-coded folio reference count calculations with the > folio_expected_ref_count() helper to improve code maintainability > and reduce duplication. > > No functional changes intended. > > Signed-off-by: Shivank Garg > --- > kernel/events/uprobes.c | 5 +++-- > mm/memfd.c | 4 ++-- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 4c965ba77f9f..c978c8c27340 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -434,10 +434,11 @@ static int __uprobe_write_opcode(struct vm_area_struct *vma, > /* > * When unregistering, we may only zap a PTE if uffd is disabled and > * there are no unexpected folio references ... > + * Expected refs: mappings + swapcache. > + * We hold one additional reference (+1). > */ > if (is_register || userfaultfd_missing(vma) || > - (folio_ref_count(folio) != folio_mapcount(folio) + 1 + > - folio_test_swapcache(folio) * folio_nr_pages(folio))) > + (folio_ref_count(folio) != folio_expected_ref_count(folio) + 1)) > goto remap; > With the comment removed (the caller holds a reference from GUP) or simplified ("Caller holds an additional folio reference.") Acked-by: David Hildenbrand -- Cheers, David / dhildenb