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[2003:cb:c734:b800:12c4:65cd:348a:aee6]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-38dd9c48173sm5308677f8f.37.2025.02.10.11.39.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 10 Feb 2025 11:39:04 -0800 (PST) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, nouveau@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, damon@lists.linux.dev, David Hildenbrand , Andrew Morton , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Jonathan Corbet , Alex Shi , Yanteng Si , Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , SeongJae Park , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pasha Tatashin , Peter Xu , Alistair Popple , Jason Gunthorpe Subject: [PATCH v2 16/17] mm/rmap: keep mapcount untouched for device-exclusive entries Date: Mon, 10 Feb 2025 20:37:58 +0100 Message-ID: <20250210193801.781278-17-david@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250210193801.781278-1-david@redhat.com> References: <20250210193801.781278-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 9g1XwR8W-gkal9wuh8oMV_UQ5-TckhwKZqMnxGQSg-U_1739216346 X-Mimecast-Originator: redhat.com content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspam-User: X-Rspamd-Queue-Id: 6272840006 X-Stat-Signature: 35n7bftz816zhr4onwyyapdpezsnp9gf X-Rspamd-Server: rspam03 X-HE-Tag: 1739216349-250 X-HE-Meta: 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 t2Y7BjGa JmAcGJs7w+08MmPvqcjnahT7o1EjqyjuC8/RWorqybapWOCWtNoZABp0+9aSDpCD2elWuH49sb99YyOceJ8sjYN+PCTSuuyb0pBXcfc8vJSCfmpStZUqrMzQ7vdaKqirEIMODsDf/QoDrfz9nBjwTX7alx0Tl2STwbC9qd5e+mNZ/RUMCvPqNifmJWKelERoORGZg7um6yf9yNdYOlJonecRdHK/b26YMtOurrV6sh760K14ryLr0W7KPm8u6K7Z6BZ66sZFr3X+4Y+gLTnyhOxM4TsOwLaZKQSKSgkYPF4jNfjb5FD63WIntfZL0LwwBBJsdLheBzor0uMsAS8HTtiolPtebaBF12C3ROSGGOj+U+QyF85OHMuuOqMhZjq/hzyPuRy/bSnujTIhCJJCvwg83O2CzWkAqzGhVZC5Gb+etEA1zODWMJ2I3KGAhR1QmXwVj624AmnhUFVI2L867pp6VWKwrYMHrWHPp X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Now that conversion to device-exclusive does no longer perform an rmap walk and all page_vma_mapped_walk() users were taught to properly handle device-exclusive entries, let's treat device-exclusive entries just as if they would be present, similar to how we handle device-private entries already. This fixes swapout/migration/split/hwpoison of folios with device-exclusive entries. We only had to take care of page_vma_mapped_walk() users, because these traditionally assume pte_present(). Other page table walkers already have to handle !pte_present(), and some of them might simply skip them (e.g., MADV_PAGEOUT) if they are not specialized on them. This change doesn't modify the latter. Note that while folios with device-exclusive PTEs can now get migrated, khugepaged will not collapse a THP if there is device-exclusive PTE. Doing so might also not be desired if the device frequently performs atomics to the same page. Similarly, KSM will never merge order-0 folios that are device-exclusive. Fixes: b756a3b5e7ea ("mm: device exclusive memory access") Signed-off-by: David Hildenbrand --- mm/memory.c | 17 +---------------- mm/rmap.c | 7 ------- 2 files changed, 1 insertion(+), 23 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index ba33ba3b7ea17..e9f54065b117f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -741,20 +741,6 @@ static void restore_exclusive_pte(struct vm_area_struct *vma, VM_BUG_ON_FOLIO(pte_write(pte) && (!folio_test_anon(folio) && PageAnonExclusive(page)), folio); - - /* - * No need to take a page reference as one was already - * created when the swap entry was made. - */ - if (folio_test_anon(folio)) - folio_add_anon_rmap_pte(folio, page, vma, address, RMAP_NONE); - else - /* - * Currently device exclusive access only supports anonymous - * memory so the entry shouldn't point to a filebacked page. - */ - WARN_ON_ONCE(1); - set_pte_at(vma->vm_mm, address, ptep, pte); /* @@ -1626,8 +1612,7 @@ static inline int zap_nonpresent_ptes(struct mmu_gather *tlb, */ WARN_ON_ONCE(!vma_is_anonymous(vma)); rss[mm_counter(folio)]--; - if (is_device_private_entry(entry)) - folio_remove_rmap_pte(folio, page, vma); + folio_remove_rmap_pte(folio, page, vma); folio_put(folio); } else if (!non_swap_entry(entry)) { /* Genuine swap entries, hence a private anon pages */ diff --git a/mm/rmap.c b/mm/rmap.c index 7b737f0f68fb5..e2a543f639ce3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2511,13 +2511,6 @@ struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr, /* The pte is writable, uffd-wp does not apply. */ set_pte_at(mm, addr, fw.ptep, swp_pte); - /* - * TODO: The device-exclusive PFN swap PTE holds a folio reference but - * does not count as a mapping (mapcount), which is wrong and must be - * fixed, otherwise RMAP walks don't behave as expected. - */ - folio_remove_rmap_pte(folio, page, vma); - folio_walk_end(&fw, vma); mmu_notifier_invalidate_range_end(&range); *foliop = folio;