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Thu, 24 Sep 2026 21:37:36 -0700 (PDT) From: Donggeun Yoo To: Kiryl Shutsemau Cc: Donggeun Yoo , akpm@linux-foundation.org, rppt@kernel.org, peterx@redhat.com, surenb@google.com, aarcange@redhat.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, mhocko@suse.com, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v1 1/2] userfaultfd: clear the inherited uffd bit in move_swap_pte() Date: Fri, 25 Sep 2026 13:37:29 +0900 Message-ID: <20260925043729.2362287-1-donggeunyoo.kernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: <20260919004630.1159895-1-donggeunyoo.kernel@gmail.com> <20260919004630.1159895-2-donggeunyoo.kernel@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B4C81120006 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: r1rk1sne5hwk6bqdzhjtmbnzn58ah567 X-HE-Tag: 1790311057-434970 X-HE-Meta: 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 /3pdmZJQ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 23, 2026 at 12:18:30PM +0100, Kiryl Shutsemau wrote: > Putting it in the 'else' is wrong. Clear uffd on the source > unconditionally and re-arm based on the target VMA: > > orig_src_pte = pte_swp_clear_uffd(orig_src_pte); > /* Re-arm RWP on the moved swap entry if dst_vma is RWP-registered. */ > if (userfaultfd_rwp(dst_vma)) > orig_src_pte = pte_swp_mkuffd(orig_src_pte); > > That is what move_pages_huge_pmd() does with clear_uffd_wp_pmd() before > its own re-arm, and it is the logically correct way to do this: the > source's state is gone, the destination decides. Done in v2: https://lore.kernel.org/all/20260925042907.2330519-1-donggeunyoo.kernel@gmail.com/ Thanks, Donggeun