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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id q67-20020a818046000000b0054f83731ad2sm314580ywf.0.2023.06.08.18.34.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 18:34:06 -0700 (PDT) Date: Thu, 8 Jun 2023 18:34:03 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 20/32] mm/madvise: clean up pte_offset_map_lock() scans In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Came here to make madvise's several pte_offset_map_lock() scans advance to next extent on failure, and remove superfluous pmd_trans_unstable() and pmd_none_or_trans_huge_or_clear_bad() calls. But also did some nearby cleanup. swapin_walk_pmd_entry(): don't name an address "index"; don't drop the lock after every pte, only when calling out to read_swap_cache_async(). madvise_cold_or_pageout_pte_range() and madvise_free_pte_range(): prefer "start_pte" for pointer, orig_pte usually denotes a saved pte value; leave lazy MMU mode before unlocking; merge the success and failure paths after split_folio(). Signed-off-by: Hugh Dickins --- mm/madvise.c | 122 ++++++++++++++++++++++++++++----------------------- 1 file changed, 68 insertions(+), 54 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index b5ffbaf616f5..0af64c4a8f82 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -188,37 +188,43 @@ static int madvise_update_vma(struct vm_area_struct *vma, #ifdef CONFIG_SWAP static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start, - unsigned long end, struct mm_walk *walk) + unsigned long end, struct mm_walk *walk) { struct vm_area_struct *vma = walk->private; - unsigned long index; struct swap_iocb *splug = NULL; + pte_t *ptep = NULL; + spinlock_t *ptl; + unsigned long addr; - if (pmd_none_or_trans_huge_or_clear_bad(pmd)) - return 0; - - for (index = start; index != end; index += PAGE_SIZE) { + for (addr = start; addr < end; addr += PAGE_SIZE) { pte_t pte; swp_entry_t entry; struct page *page; - spinlock_t *ptl; - pte_t *ptep; - ptep = pte_offset_map_lock(vma->vm_mm, pmd, index, &ptl); + if (!ptep++) { + ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + if (!ptep) + break; + } + pte = *ptep; - pte_unmap_unlock(ptep, ptl); - if (!is_swap_pte(pte)) continue; entry = pte_to_swp_entry(pte); if (unlikely(non_swap_entry(entry))) continue; + pte_unmap_unlock(ptep, ptl); + ptep = NULL; + page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE, - vma, index, false, &splug); + vma, addr, false, &splug); if (page) put_page(page); } + + if (ptep) + pte_unmap_unlock(ptep, ptl); swap_read_unplug(splug); cond_resched(); @@ -340,7 +346,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, bool pageout = private->pageout; struct mm_struct *mm = tlb->mm; struct vm_area_struct *vma = walk->vma; - pte_t *orig_pte, *pte, ptent; + pte_t *start_pte, *pte, ptent; spinlock_t *ptl; struct folio *folio = NULL; LIST_HEAD(folio_list); @@ -422,11 +428,11 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, } regular_folio: - if (pmd_trans_unstable(pmd)) - return 0; #endif tlb_change_page_size(tlb, PAGE_SIZE); - orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + if (!start_pte) + return 0; flush_tlb_batched_pending(mm); arch_enter_lazy_mmu_mode(); for (; addr < end; pte++, addr += PAGE_SIZE) { @@ -447,25 +453,28 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, * are sure it's worth. Split it if we are only owner. */ if (folio_test_large(folio)) { + int err; + if (folio_mapcount(folio) != 1) break; if (pageout_anon_only_filter && !folio_test_anon(folio)) break; + if (!folio_trylock(folio)) + break; folio_get(folio); - if (!folio_trylock(folio)) { - folio_put(folio); - break; - } - pte_unmap_unlock(orig_pte, ptl); - if (split_folio(folio)) { - folio_unlock(folio); - folio_put(folio); - orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl); - break; - } + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(start_pte, ptl); + start_pte = NULL; + err = split_folio(folio); folio_unlock(folio); folio_put(folio); - orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (err) + break; + start_pte = pte = + pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!start_pte) + break; + arch_enter_lazy_mmu_mode(); pte--; addr -= PAGE_SIZE; continue; @@ -510,8 +519,10 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, folio_deactivate(folio); } - arch_leave_lazy_mmu_mode(); - pte_unmap_unlock(orig_pte, ptl); + if (start_pte) { + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(start_pte, ptl); + } if (pageout) reclaim_pages(&folio_list); cond_resched(); @@ -612,7 +623,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, struct mm_struct *mm = tlb->mm; struct vm_area_struct *vma = walk->vma; spinlock_t *ptl; - pte_t *orig_pte, *pte, ptent; + pte_t *start_pte, *pte, ptent; struct folio *folio; int nr_swap = 0; unsigned long next; @@ -620,13 +631,12 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, next = pmd_addr_end(addr, end); if (pmd_trans_huge(*pmd)) if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next)) - goto next; - - if (pmd_trans_unstable(pmd)) - return 0; + return 0; tlb_change_page_size(tlb, PAGE_SIZE); - orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + start_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!start_pte) + return 0; flush_tlb_batched_pending(mm); arch_enter_lazy_mmu_mode(); for (; addr != end; pte++, addr += PAGE_SIZE) { @@ -664,23 +674,26 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, * deactivate all pages. */ if (folio_test_large(folio)) { + int err; + if (folio_mapcount(folio) != 1) - goto out; + break; + if (!folio_trylock(folio)) + break; folio_get(folio); - if (!folio_trylock(folio)) { - folio_put(folio); - goto out; - } - pte_unmap_unlock(orig_pte, ptl); - if (split_folio(folio)) { - folio_unlock(folio); - folio_put(folio); - orig_pte = pte_offset_map_lock(mm, pmd, addr, &ptl); - goto out; - } + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(start_pte, ptl); + start_pte = NULL; + err = split_folio(folio); folio_unlock(folio); folio_put(folio); - orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl); + if (err) + break; + start_pte = pte = + pte_offset_map_lock(mm, pmd, addr, &ptl); + if (!start_pte) + break; + arch_enter_lazy_mmu_mode(); pte--; addr -= PAGE_SIZE; continue; @@ -725,17 +738,18 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, } folio_mark_lazyfree(folio); } -out: + if (nr_swap) { if (current->mm == mm) sync_mm_rss(mm); - add_mm_counter(mm, MM_SWAPENTS, nr_swap); } - arch_leave_lazy_mmu_mode(); - pte_unmap_unlock(orig_pte, ptl); + if (start_pte) { + arch_leave_lazy_mmu_mode(); + pte_unmap_unlock(start_pte, ptl); + } cond_resched(); -next: + return 0; } -- 2.35.3