From nobody Fri Dec 19 04:07:47 2025 Received: from mail-qt1-f202.google.com (mail-qt1-f202.google.com [209.85.160.202]) (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 BD83322DFB3 for ; Thu, 27 Feb 2025 13:32:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740663162; cv=none; b=VAlupGbUmSO9VaWfpsTWc1nHqGgZzxCceWDyo8/PUISrJEaUAOqSS7BSJd1xTPvQqXPaMcxwashVgBmmeVZTsFHLJ4Q2jl/ha6iAx4pZ0WBopFNX91Pg9HeLoojMakSXISO5ut1DsVxcDSCwGxHkXszdjzUtnBqVwuLIWlVNC4c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740663162; c=relaxed/simple; bh=ZkqjquJmqyKCF3YVGXF3s6NPgWRXSZRfFKpweGnRmXM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=qxR9sikqk8yyHdK0G8o2J+tvGZx3RfRKnSK58wUsWRikVhXMvldypyU9Qu2zSWzN92Xf2gXv/YydmDzBRj8TnK/oQOb1GVySGpnYGO9tssmYLN1Nus3dQ9bDpd3kwPDf5Yaj4Fso5BbJ8dx2h+ZVwQIiH5/0qXRTsfAXO/Gz89A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--bgeffon.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=PZ5Cer2V; arc=none smtp.client-ip=209.85.160.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--bgeffon.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="PZ5Cer2V" Received: by mail-qt1-f202.google.com with SMTP id d75a77b69052e-47217c14be9so31388381cf.1 for ; Thu, 27 Feb 2025 05:32:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740663158; x=1741267958; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=HyfS+UvHxKI14QQn8t0ml/VJXb1kYrctFLX+Mu/t1JE=; b=PZ5Cer2VvgawBAiwj32e9OgWrX0Wc/394uBq8zscQBGuxPx+G3JcasoxLfxmnNxGKB nHfvWjIfcacTtvsNFpK7Ohv9QpDnHZTScQseyAxAorFzDzvultHWOpWwSh0y7VpEeby3 xdOwH0IBEJS4LcH55uubqIdfAFB7en2Ztd37U2i6Agt6tW1MmZm4UkxY7gW38j8djDED yr6WAWavJsNA6B69QZH2WW7CcS8uqNQVl94ZC0BmjYd/HSgmr8rLbHsXK4S2IIX2pF+6 V/ZHlv2d89OBWciWU2/GNJZQm+MXcbWU8+xE4Ym73yMKrHPmg8BkZlWRyPBtE6u3anxM xt1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740663158; x=1741267958; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=HyfS+UvHxKI14QQn8t0ml/VJXb1kYrctFLX+Mu/t1JE=; b=NfwdKffZsu5QLHZ4f2IxxrVxTHH8Rf+dp3cHqR8sxIit/JPqVDqFvHb3ZvGT2xpXdM SbG8j3VfN0RzeSNvccbUJ5vLSJSlunyvADofBHYAFMBTE5NqK/yj+nvueQumnLkNEtVQ FpPVnl2JurSlMiKq1T90yef0UrBa4C+LJkC+Pn+XjAQK6Rl6JlrafN/1uoC4cQWhMJmn TzkvZ0Gi9ovGLbbdPTFHjLs+FUqNaDZaIjsvk26dYTV1+6UXXbk2kejdPY1mg88PqWQY sO1D0vpVSdqrM+Q9enueI+VYTUvw9m4fsxoLgw320Usg/8YCo3fjGDLdporOouicBe88 t0XA== X-Forwarded-Encrypted: i=1; AJvYcCU4yDJzMhZPZQBKV1s4nF7chLEtcH62XE95fOI7KanO/jKpwOSNzE6aSAyCNMZYjpmSLmx78dm0Kh7GSYc=@vger.kernel.org X-Gm-Message-State: AOJu0Yzz5ffGSKOYr8gKECzT3EOGezcFsunc+xO9wuSfdaV/FjIJbA6/ A87WRPyGQxfcWI3pPvYB4Po59CRH/2Pue74/KFxYZWTgj5/w8iX+fxgM8E+ED2f20RsiKDGLk8+ hS+jgyQ== X-Google-Smtp-Source: AGHT+IHvETM3+pn2QTpJ1tsLr3mG9ApdH9Fim1Cx8ibw/PLC8WURMDcwwL5DzLuRErYfJClH2Bb5qxGCi7L2 X-Received: from qtbcm27.prod.google.com ([2002:a05:622a:251b:b0:472:122b:3255]) (user=bgeffon job=prod-delivery.src-stubby-dispatcher) by 2002:ac8:5d16:0:b0:472:1573:fa9c with SMTP id d75a77b69052e-47377118705mr141991131cf.6.1740663158655; Thu, 27 Feb 2025 05:32:38 -0800 (PST) Date: Thu, 27 Feb 2025 08:32:36 -0500 In-Reply-To: <20250226114815.758217-1-bgeffon@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250226114815.758217-1-bgeffon@google.com> X-Mailer: git-send-email 2.48.1.711.g2feabab25a-goog Message-ID: <20250227133236.1296853-1-bgeffon@google.com> Subject: [PATCH v3] mm: fix finish_fault() handling for large folios From: Brian Geffon To: Andrew Morton Cc: Zi Yan , Kefeng Wang , Suren Baghdasaryan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox , David Hildenbrand , Brian Geffon , stable@vger.kernel.org, Hugh Dickins , Baolin Wang , Marek Maslanka Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When handling faults for anon shmem finish_fault() will attempt to install ptes for the entire folio. Unfortunately if it encounters a single non-pte_none entry in that range it will bail, even if the pte that triggered the fault is still pte_none. When this situation happens the fault will be retried endlessly never making forward progress. This patch fixes this behavior and if it detects that a pte in the range is not pte_none it will fall back to setting a single pte. Cc: stable@vger.kernel.org Cc: Hugh Dickins Fixes: 43e027e41423 ("mm: memory: extend finish_fault() to support large fo= lio") Suggested-by: Baolin Wang Reported-by: Marek Maslanka Signed-off-by: Brian Geffon --- mm/memory.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index b4d3d4893267..f3054bbb3c1e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5183,7 +5183,11 @@ vm_fault_t finish_fault(struct vm_fault *vmf) bool is_cow =3D (vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED); int type, nr_pages; - unsigned long addr =3D vmf->address; + unsigned long addr; + bool needs_fallback =3D false; + +fallback: + addr =3D vmf->address; =20 /* Did we COW the page? */ if (is_cow) @@ -5222,7 +5226,8 @@ vm_fault_t finish_fault(struct vm_fault *vmf) * approach also applies to non-anonymous-shmem faults to avoid * inflating the RSS of the process. */ - if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) { + if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma)) || + unlikely(needs_fallback)) { nr_pages =3D 1; } else if (nr_pages > 1) { pgoff_t idx =3D folio_page_idx(folio, page); @@ -5258,9 +5263,9 @@ vm_fault_t finish_fault(struct vm_fault *vmf) ret =3D VM_FAULT_NOPAGE; goto unlock; } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) { - update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages); - ret =3D VM_FAULT_NOPAGE; - goto unlock; + needs_fallback =3D true; + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto fallback; } =20 folio_ref_add(folio, nr_pages - 1); --=20 2.48.1.711.g2feabab25a-goog