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Thu, 15 Oct 2026 19:02:43 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Fri, 16 Oct 2026 02:02:42 +0000 Message-Id: Cc: , , , Subject: Re: [PATCH bpf-next v4 2/8] bpf: Associate arena pages with their mapping From: "Alexei Starovoitov" To: "Emil Tsalapatis" , In-Reply-To: <20261014233442.8392-3-emil@etsalapatis.com> References: <20261014233442.8392-1-emil@etsalapatis.com> <20261014233442.8392-3-emil@etsalapatis.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, Oct 14, 2026 at 11:34 PM Emil Tsalapatis wrote: > Associate arena backing pages with the arena's private mapping and set > their page offsets. This allows the fault handler to delegate user PTE > installation to generic MM code, which is itself useful for avoiding > races with kfunc-related arena operations. arena_vm_fault() returns vmf->page and finish_fault() installs the pte today. That doesn't need page->mapping. VM_FAULT_LOCKED doesn't either. tcmu_vma_fault() returns it for alloc_page()-ed pages. mm folks were removing page->mapping and index from drivers. See commit 6cdef2ddce2b ("fb_defio: do not use deprecated page->mapping, index fields"). [...] > +/* Arena pages are not page-cache entries and must not be evicted by MM. */ > +static bool arena_release_folio(struct folio *folio, gfp_t gfp) > +{ > + return false; > +} The only place that looks at folio->mapping because of VM_FAULT_LOCKED is PageHWPoison() branch in __do_fault(). If that's the reason for this patch then check PageHWPoison() in arena_vm_fault() and return VM_FAULT_HWPOISON. Drop this patch.