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Biederman" , Andy Lutomirski , Sebastian Andrzej Siewior , "Liam R. Howlett" , Fenghua Yu , Andrei Vagin , Barret Rhoden , Michal Hocko , "Jason A. Donenfeld" , Alexey Gladkov , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Dinglan Peng , Pedro Fonseca , Jim Huang , Huichun Feng , Chih-En Lin Subject: [PATCH v4 04/14] mm/rmap: Break COW PTE in rmap walking Date: Tue, 7 Feb 2023 11:51:29 +0800 Message-Id: <20230207035139.272707-5-shiyn.lin@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230207035139.272707-1-shiyn.lin@gmail.com> References: <20230207035139.272707-1-shiyn.lin@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org Some of the features (unmap, migrate, device exclusive, mkclean, etc) might modify the pte entry via rmap. Add a new page vma mapped walk flag, PVMW_BREAK_COW_PTE, to indicate the rmap walking to break COW PTE. Signed-off-by: Chih-En Lin --- include/linux/rmap.h | 2 ++ mm/migrate.c | 3 ++- mm/page_vma_mapped.c | 4 ++++ mm/rmap.c | 9 +++++---- mm/vmscan.c | 3 ++- 5 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index bd3504d11b15..d0f07e551973 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -368,6 +368,8 @@ int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, #define PVMW_SYNC (1 << 0) /* Look for migration entries rather than present PTEs */ #define PVMW_MIGRATION (1 << 1) +/* Break COW-ed PTE during walking */ +#define PVMW_BREAK_COW_PTE (1 << 2) struct page_vma_mapped_walk { unsigned long pfn; diff --git a/mm/migrate.c b/mm/migrate.c index a4d3fc65085f..04376ce05aa8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -183,7 +183,8 @@ void putback_movable_pages(struct list_head *l) static bool remove_migration_pte(struct folio *folio, struct vm_area_struct *vma, unsigned long addr, void *old) { - DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, PVMW_SYNC | PVMW_MIGRATION); + DEFINE_FOLIO_VMA_WALK(pvmw, old, vma, addr, + PVMW_SYNC | PVMW_MIGRATION | PVMW_BREAK_COW_PTE); while (page_vma_mapped_walk(&pvmw)) { rmap_t rmap_flags = RMAP_NONE; diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index 93e13fc17d3c..7b35e85b9964 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -251,6 +251,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) step_forward(pvmw, PMD_SIZE); continue; } + if (pvmw->flags & PVMW_BREAK_COW_PTE) { + if (break_cow_pte(vma, pvmw->pmd, pvmw->address)) + return not_found(pvmw); + } if (!map_pte(pvmw)) goto next_pte; this_pte: diff --git a/mm/rmap.c b/mm/rmap.c index b616870a09be..bce97496b1f6 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1012,7 +1012,8 @@ static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw) static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma, unsigned long address, void *arg) { - DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC); + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, + PVMW_SYNC | PVMW_BREAK_COW_PTE); int *cleaned = arg; *cleaned += page_vma_mkclean_one(&pvmw); @@ -1463,7 +1464,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, unsigned long address, void *arg) { struct mm_struct *mm = vma->vm_mm; - DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_BREAK_COW_PTE); pte_t pteval; struct page *subpage; bool anon_exclusive, ret = true; @@ -1834,7 +1835,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, unsigned long address, void *arg) { struct mm_struct *mm = vma->vm_mm; - DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_BREAK_COW_PTE); pte_t pteval; struct page *subpage; bool anon_exclusive, ret = true; @@ -2187,7 +2188,7 @@ static bool page_make_device_exclusive_one(struct folio *folio, struct vm_area_struct *vma, unsigned long address, void *priv) { struct mm_struct *mm = vma->vm_mm; - DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_BREAK_COW_PTE); struct make_exclusive_args *args = priv; pte_t pteval; struct page *subpage; diff --git a/mm/vmscan.c b/mm/vmscan.c index bf3eedf0209c..15eda32146fd 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1882,7 +1882,8 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, /* * The folio is mapped into the page tables of one or more - * processes. Try to unmap it here. + * processes. Try to unmap it here. Also, since it will write + * to the page tables, break COW PTE if they are. */ if (folio_mapped(folio)) { enum ttu_flags flags = TTU_BATCH_FLUSH;