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[73.93.239.127]) by smtp.gmail.com with ESMTPSA id m14sm76733pff.17.2021.05.26.13.12.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 May 2021 13:12:43 -0700 (PDT) From: Yang Shi To: hughd@google.com, ziy@nvidia.com, kirill.shutemov@linux.intel.com, minchan@kernel.org, naoya.horiguchi@nec.com, wangyugui@e16-tech.com, akpm@linux-foundation.org Cc: shy828301@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [v4 PATCH 2/2] mm: rmap: make try_to_unmap() void function Date: Wed, 26 May 2021 13:12:39 -0700 Message-Id: <20210526201239.3351-2-shy828301@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210526201239.3351-1-shy828301@gmail.com> References: <20210526201239.3351-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently try_to_unmap() return bool value by checking page_mapcount(), however this may return false positive since page_mapcount() doesn't check all subpages of compound page. The total_mapcount() could be used instead, but its cost is higher since it traverses all subpages. Actually the most callers of try_to_unmap() don't care about the return value at all. So just need check if page is still mapped by page_mapped() when necessary. And page_mapped() does bail out early when it finds mapped subpage. Suggested-by: Hugh Dickins Acked-by: Hugh Dickins Signed-off-by: Yang Shi --- v4: Updated the comment of try_to_unmap() per Minchan. Minor fix and patch reorder per Hugh. Collected ack tag from Hugh. include/linux/rmap.h | 2 +- mm/memory-failure.c | 15 +++++++-------- mm/rmap.c | 7 +++---- mm/vmscan.c | 3 ++- 4 files changed, 13 insertions(+), 14 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index def5c62c93b3..116cb193110a 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -194,7 +194,7 @@ static inline void page_dup_rmap(struct page *page, bool compound) int page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg, unsigned long *vm_flags); -bool try_to_unmap(struct page *, enum ttu_flags flags); +void try_to_unmap(struct page *, enum ttu_flags flags); /* Avoid racy checks */ #define PVMW_SYNC (1 << 0) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 9dcc9bcea731..07e462588df9 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1063,7 +1063,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, enum ttu_flags ttu = TTU_IGNORE_MLOCK; struct address_space *mapping; LIST_HEAD(tokill); - bool unmap_success = true; + bool unmap_success; int kill = 1, forcekill; struct page *hpage = *hpagep; bool mlocked = PageMlocked(hpage); @@ -1126,7 +1126,7 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED); if (!PageHuge(hpage)) { - unmap_success = try_to_unmap(hpage, ttu); + try_to_unmap(hpage, ttu); } else { if (!PageAnon(hpage)) { /* @@ -1138,17 +1138,16 @@ static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, */ mapping = hugetlb_page_mapping_lock_write(hpage); if (mapping) { - unmap_success = try_to_unmap(hpage, - ttu|TTU_RMAP_LOCKED); + try_to_unmap(hpage, ttu|TTU_RMAP_LOCKED); i_mmap_unlock_write(mapping); - } else { + } else pr_info("Memory failure: %#lx: could not lock mapping for mapped huge page\n", pfn); - unmap_success = false; - } } else { - unmap_success = try_to_unmap(hpage, ttu); + try_to_unmap(hpage, ttu); } } + + unmap_success = !page_mapped(hpage); if (!unmap_success) pr_err("Memory failure: %#lx: failed to unmap page (mapcount=%d)\n", pfn, page_mapcount(hpage)); diff --git a/mm/rmap.c b/mm/rmap.c index a35cbbbded0d..d4e0d89726b8 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1749,9 +1749,10 @@ static int page_not_mapped(struct page *page) * Tries to remove all the page table entries which are mapping this * page, used in the pageout path. Caller must hold the page lock. * - * If unmap is successful, return true. Otherwise, false. + * It is the callers' responsibility to check if the page is still + * mapped when needed. */ -bool try_to_unmap(struct page *page, enum ttu_flags flags) +void try_to_unmap(struct page *page, enum ttu_flags flags) { struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, @@ -1776,8 +1777,6 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags) rmap_walk_locked(page, &rwc); else rmap_walk(page, &rwc); - - return !page_mapcount(page) ? true : false; } /** diff --git a/mm/vmscan.c b/mm/vmscan.c index f96d62159720..fa5052ace415 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1499,7 +1499,8 @@ static unsigned int shrink_page_list(struct list_head *page_list, if (unlikely(PageTransHuge(page))) flags |= TTU_SPLIT_HUGE_PMD; - if (!try_to_unmap(page, flags)) { + try_to_unmap(page, flags); + if (page_mapped(page)) { stat->nr_unmap_fail += nr_pages; if (!was_swapbacked && PageSwapBacked(page)) stat->nr_lazyfree_fail += nr_pages; -- 2.26.2