From nobody Fri Dec 19 16:53:31 2025 Received: from mail-pg1-f180.google.com (mail-pg1-f180.google.com [209.85.215.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 34C7B1CF7AF for ; Wed, 4 Sep 2024 08:41:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725439284; cv=none; b=liQxwAiJa3VOyRlGvUZGZbnOR1oXyOyEsTOCguO7wlYXZXEwdStmne3MzTpuLGkWgQgurCVWUgS6xyIav3hYykty6NmZbsxy+ddvG8F6M6EQBSyAxo6rsMsG7vVpBDATcV309CwOVjDEGLF+8YJljHn2Zrta0GyCT7VPEAhWUro= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725439284; c=relaxed/simple; bh=hlsEpWmf1qa6LsjjHd7NQfjzneKSvrpzaH+0KKra15I=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=lOK0xI29+Q21XjVjCXNNAHGqMgC22KxjVg2L2KUwTmZ0DSA8AGdUoHPpwMKK6qlRXU2wMKDLdxFEUbQ2izEqAz8xGt0CjKV49j2SlCZ+VjtBlVlwwRtV94D+DKMmk9gnIz2GHsbBOliNgONr4wexwKzmu1gFpbU1a/t9t8H/Mbw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=TzmGGeR4; arc=none smtp.client-ip=209.85.215.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="TzmGGeR4" Received: by mail-pg1-f180.google.com with SMTP id 41be03b00d2f7-6e7b121be30so3911056a12.1 for ; Wed, 04 Sep 2024 01:41:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1725439282; x=1726044082; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=pGIEfQHzsThgJvUA20OC+gjd0SFgF9+h9gc5ip8dlng=; b=TzmGGeR4OjyX+vdh9g+O+p7U0yyJ/FyMALADy2OCaQb2zk/lzTGCVXr+EFq37k2pJ4 S7n4uaEhKptnQF8CKhAD2cBULWvseCQ944xVQIQUtMpYVeUOX7IUuMPpSHolemlv1KUw CaT/4mH/WNBuLR6Qjyojxxr5UdpbKPN67bEiJucMBkarx2uUD3i0aAQz6crTJA1GWf2Z e7hY/QAInIwnDppxsA/wl9kardvOy49E3dT2wlJ4kXn646/PRpeIXxYju6fgNaK+BenU kT8VGTcYQwo/YpJ83pLJwcqHlxaqutvj964tPqfTzkTs/6NtKmgG3LHX8ZpDp01EQ1Vk Icbw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1725439282; x=1726044082; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=pGIEfQHzsThgJvUA20OC+gjd0SFgF9+h9gc5ip8dlng=; b=Z0kRY93/bO6Vi65fsGYEno603f10aeRaWdsopG52/VvoDE7FB47hyAIK50Us9SeUoJ D6LwqkOnjGZJmr0XHL18Xw/32GaSSCCwPiiUPP+AhXILQARExkK9SmI1809u1WtFqd6j RHy7G/1eBwH4LWYf75tVE+JvfLM2Qk2vECq5LmipVp/oxpSb0GNyZ1BT8mDTK5sC9363 IQcDobfctvf5WYM9F1vJLiHuFqtL7OYYkuPLvVyYTz7We89deobDQwBV5Q5XR09D2HAx bVLNGQPSFB3hYNm/BAEo0wBSCp6JWdOux9fs4d0j3zAiAs1r4xNc7T6op87RT5coEyoj mwNg== X-Gm-Message-State: AOJu0YzLVG22pV0wsfE20gaz+0OHvH9ZnlDY95AXS0aWyFZgCqQvBpyJ MbRfX73Vjwfsr+wxrYB1H++LLpM9Oe9gfxnM1Rt7wkb4+DTE5w7hsH15dA6e7SU= X-Google-Smtp-Source: AGHT+IGQLG6wPNgDOgfzFUGIly89eF+GLm9izjxQGbRYP1g8ZSKlFJK5pYdbKQOnPMpn9+eqCP/7EQ== X-Received: by 2002:a05:6a21:2d86:b0:1c8:b65b:3db8 with SMTP id adf61e73a8af0-1ced607378emr11775108637.9.1725439282360; Wed, 04 Sep 2024 01:41:22 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([139.177.225.242]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-206ae95a51csm9414045ad.117.2024.09.04.01.41.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Sep 2024 01:41:22 -0700 (PDT) From: Qi Zheng To: david@redhat.com, hughd@google.com, willy@infradead.org, muchun.song@linux.dev, vbabka@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, vishal.moola@gmail.com, peterx@redhat.com, ryan.roberts@arm.com, christophe.leroy2@cs-soprasteria.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, Qi Zheng Subject: [PATCH v3 06/14] mm: handle_pte_fault() use pte_offset_map_rw_nolock() Date: Wed, 4 Sep 2024 16:40:14 +0800 Message-Id: <20240904084022.32728-7-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20240904084022.32728-1-zhengqi.arch@bytedance.com> References: <20240904084022.32728-1-zhengqi.arch@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In handle_pte_fault(), we may modify the vmf->pte after acquiring the vmf->ptl, so convert it to using pte_offset_map_rw_nolock(). But since we will do the pte_same() check, so there is no need to get pmdval to do pmd_same() check, just pass a dummy variable to it. Signed-off-by: Qi Zheng Acked-by: David Hildenbrand Reviewed-by: Muchun Song --- mm/memory.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 42674c0748cba..06674f94b7a4e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5498,14 +5498,24 @@ static vm_fault_t handle_pte_fault(struct vm_fault = *vmf) vmf->pte =3D NULL; vmf->flags &=3D ~FAULT_FLAG_ORIG_PTE_VALID; } else { + pmd_t dummy_pmdval; + /* * A regular pmd is established and it can't morph into a huge * pmd by anon khugepaged, since that takes mmap_lock in write * mode; but shmem or file collapse to THP could still morph * it into a huge pmd: just retry later if so. + * + * Use the maywrite version to indicate that vmf->pte may be + * modified, but since we will use pte_same() to detect the + * change of the !pte_none() entry, there is no need to recheck + * the pmdval. Here we chooes to pass a dummy variable instead + * of NULL, which helps new user think about why this place is + * special. */ - vmf->pte =3D pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); + vmf->pte =3D pte_offset_map_rw_nolock(vmf->vma->vm_mm, vmf->pmd, + vmf->address, &dummy_pmdval, + &vmf->ptl); if (unlikely(!vmf->pte)) return 0; vmf->orig_pte =3D ptep_get_lockless(vmf->pte); --=20 2.20.1