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[2003:d8:2f0d:f000:eec9:2b8d:4913:f32a]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-450d7fa21e4sm180154785e9.11.2025.06.03.14.16.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Jun 2025 14:16:38 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, David Hildenbrand , Andrew Morton , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Dan Williams Subject: [PATCH v1 1/2] mm/huge_memory: don't mark refcounted pages special in vmf_insert_folio_pmd() Date: Tue, 3 Jun 2025 23:16:33 +0200 Message-ID: <20250603211634.2925015-2-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250603211634.2925015-1-david@redhat.com> References: <20250603211634.2925015-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: W4S6X9Wpqr5BqmYaGUEpsTBADBnP9OOnMMu0yK_6A5w_1748985399 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Queue-Id: E9F0E2000A X-Stat-Signature: h1i34b6cuc4rajbc8nxb3f8yt4oj6qzo X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1748985403-743033 X-HE-Meta: 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 U8iYiqA+ cfzwQPqO/FIbKn7DgduPIVGtGqclLREZhGkAt16kzCYy6jazhnpjleMgh8127ehCmsGL/8UYFjHTr0kitFfGYnkKap+UR7USC4n/9zqQy8tlGlvh7R4ueH7lvdeP5fQkyQjAVWS6qssu8v3UOLZUWAfwwA4wq1hAi8wM+bVdOY+pfL6uh27xJxkVUjc/SXjShX6hk04/ST15iIDyBjD20L7j6acXCNtebOdhIEzc0UEPR+wG9RZ3L0DyBrdIXJn70IVxb20O2O/VhrbmJwVxtRvQASiQHwovXdjb5IkmFTHa+M6CQ8NZw+XEXzSn6jAF1ZYzH+cMaag56+1LjZsi+K0DyLiBjiAb8kOjXWOklfPhlAQ7v2m5AGd64eMkMp4FRpU6F/8Vukf4F1ZvZp7M9wgsrfJylfOUE0kuQUY7Jt7Lp8DxkYwFQGMRn4vwPS3kxlZm8QWNCz/nVTpNvBoiKHTVdzPoM/iD53jj0ENQfZ8W70Nmx/6AHjvTgYv/CfaWV+4hkrtkUibp+7cqxO2MOXGfrDlyYbjohbf0E X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Marking PMDs that map a "normal" refcounted folios as special is against our rules documented for vm_normal_page(). Fortunately, there are not that many pmd_special() check that can be mislead, and most vm_normal_page_pmd()/vm_normal_folio_pmd() users that would get this wrong right now are rather harmless: e.g., none so far bases decisions whether to grab a folio reference on that decision. Well, and GUP-fast will fallback to GUP-slow. All in all, so far no big implications as it seems. Getting this right will get more important as we use folio_normal_page_pmd() in more places. Fix it by just inlining the relevant code, making the whole pmd_none() handling cleaner. We can now use folio_mk_pmd(). While at it, make sure that a pmd that is not-none is actually present before comparing PFNs. Fixes: 6c88f72691f8 ("mm/huge_memory: add vmf_insert_folio_pmd()") Signed-off-by: David Hildenbrand --- mm/huge_memory.c | 39 ++++++++++++++++++++++++++++++++------- 1 file changed, 32 insertions(+), 7 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d3e66136e41a3..f9e23dfea76f8 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1474,9 +1474,10 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf, struct folio *folio, struct vm_area_struct *vma = vmf->vma; unsigned long addr = vmf->address & PMD_MASK; struct mm_struct *mm = vma->vm_mm; + pmd_t *pmd = vmf->pmd; spinlock_t *ptl; pgtable_t pgtable = NULL; - int error; + pmd_t entry; if (addr < vma->vm_start || addr >= vma->vm_end) return VM_FAULT_SIGBUS; @@ -1490,17 +1491,41 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf, struct folio *folio, return VM_FAULT_OOM; } - ptl = pmd_lock(mm, vmf->pmd); - if (pmd_none(*vmf->pmd)) { + ptl = pmd_lock(mm, pmd); + if (pmd_none(*pmd)) { folio_get(folio); folio_add_file_rmap_pmd(folio, &folio->page, vma); add_mm_counter(mm, mm_counter_file(folio), HPAGE_PMD_NR); + + entry = folio_mk_pmd(folio, vma->vm_page_prot); + if (write) { + entry = pmd_mkyoung(pmd_mkdirty(entry)); + entry = maybe_pmd_mkwrite(entry, vma); + } + set_pmd_at(mm, addr, pmd, entry); + update_mmu_cache_pmd(vma, addr, pmd); + + if (pgtable) { + pgtable_trans_huge_deposit(mm, pmd, pgtable); + mm_inc_nr_ptes(mm); + pgtable = NULL; + } + } else if (pmd_present(*pmd) && write) { + /* + * We only allow for upgrading write permissions if the + * same folio is already mapped. + */ + if (pmd_pfn(*pmd) == folio_pfn(folio)) { + entry = pmd_mkyoung(*pmd); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) + update_mmu_cache_pmd(vma, addr, pmd); + } else { + WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); + } } - error = insert_pfn_pmd(vma, addr, vmf->pmd, - pfn_to_pfn_t(folio_pfn(folio)), vma->vm_page_prot, - write, pgtable); spin_unlock(ptl); - if (error && pgtable) + if (pgtable) pte_free(mm, pgtable); return VM_FAULT_NOPAGE; -- 2.49.0