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AJvYcCXaag765xP6d1X6KVQShydx6ePfje+Onlo4uf4hLLQAVaswJJ2EU+m2zbbHZxQlvWW2VZXjDCOEUA==@kvack.org X-Gm-Message-State: AOJu0YyVw0zErdouyXLnscASkLJpM7z5a2ebu2b3/+CoPlPoKbEie6JJ nX97cO6TWIcgHiAiYetjUolqswwZOS3dEn02alpIRytItnLvDKAWk1cI6Wy4wG6vDKkLYTuV5pv bvqaFzA== X-Google-Smtp-Source: AGHT+IGETZUu141OjsGUsrKL/0fxcfLOq3YpRMsVuVapIyy/5BXoaepYsdLR4P7IA7Dg0sPqBGRJHRWtp8Cd X-Received: from qvbml23.prod.google.com ([2002:a05:6214:5857:b0:6dd:d16:e8ab]) (user=bgeffon job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6214:130b:b0:6d4:c6d:17fe with SMTP id 6a1803df08f44-6e87ab52085mr112509186d6.25.1740587024722; Wed, 26 Feb 2025 08:23:44 -0800 (PST) Date: Wed, 26 Feb 2025 11:23:41 -0500 In-Reply-To: <20250226114815.758217-1-bgeffon@google.com> Mime-Version: 1.0 References: <20250226114815.758217-1-bgeffon@google.com> X-Mailer: git-send-email 2.48.1.711.g2feabab25a-goog Message-ID: <20250226162341.915535-1-bgeffon@google.com> Subject: [PATCH v2] 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 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 93447C0002 X-Stat-Signature: a954qopih1xkyi1ea33mwxwaayc8h8ep X-Rspam-User: X-HE-Tag: 1740587025-73023 X-HE-Meta: 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 sZbaUDVv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000016, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 folio") 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..b6c467fdbfa4 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 = (vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED); int type, nr_pages; - unsigned long addr = vmf->address; + unsigned long addr; + bool needs_fallback = false; + +fallback: + addr = vmf->address; /* 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 = 1; } else if (nr_pages > 1) { pgoff_t idx = folio_page_idx(folio, page); @@ -5258,9 +5263,9 @@ vm_fault_t finish_fault(struct vm_fault *vmf) ret = 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 = VM_FAULT_NOPAGE; - goto unlock; + needs_fallback = true; + pte_unmap_unlock(vmf->pte, vmf->ptl); + goto fallback; } folio_ref_add(folio, nr_pages - 1);