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Shutemov" , Hugh Dickins , Axel Rasmussen , Matthew Wilcox , Andrew Morton , Andrea Arcangeli , Nadav Amit Subject: [PATCH RFC 10/30] mm: Introduce zap_details.zap_flags Date: Fri, 15 Jan 2021 12:08:47 -0500 Message-Id: <20210115170907.24498-11-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210115170907.24498-1-peterx@redhat.com> References: <20210115170907.24498-1-peterx@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable 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: Instead of trying to introduce one variable for every new zap_details fie= lds, let's introduce a flag so that it can start to encode true/false informat= ions. Let's start to use this flag first to clean up the only check_mapping var= iable. Firstly, the name "check_mapping" implies this is a "boolean", but actual= ly it stores the mapping inside, just in a way that it won't be set if we don't= want to check the mapping. To make things clearer, introduce the 1st zap flag ZAP_FLAG_CHECK_MAPPING= , so that we only check against the mapping if this bit set. At the same time= , we can rename check_mapping into zap_mapping and set it always. Since at it, introduce another helper zap_check_mapping_skip() and use it= in zap_pte_range() properly. Some old comments have been removed in zap_pte_range() because they're duplicated, and since now we're with ZAP_FLAG_CHECK_MAPPING flag, it'll b= e very easy to grep this information by simply grepping the flag. It'll also make life easier when we want to e.g. pass in zap_flags into t= he callers like unmap_mapping_pages() (instead of adding new booleans beside= s the even_cows parameter). Signed-off-by: Peter Xu --- include/linux/mm.h | 19 ++++++++++++++++++- mm/memory.c | 31 ++++++++----------------------- 2 files changed, 26 insertions(+), 24 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index faf9538c13b2..2380e1df6a49 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1630,13 +1630,30 @@ static inline bool can_do_mlock(void) { return fa= lse; } extern int user_shm_lock(size_t, struct user_struct *); extern void user_shm_unlock(size_t, struct user_struct *); =20 +/* Whether to check page->mapping when zapping */ +#define ZAP_FLAG_CHECK_MAPPING BIT(0) + /* * Parameter block passed down to zap_pte_range in exceptional cases. */ struct zap_details { - struct address_space *check_mapping; /* Check page->mapping if set */ + struct address_space *zap_mapping; /* Check page->mapping if set */ + unsigned long zap_flags; /* Special flags for zapping */ }; =20 +/* Return true if skip zapping this page, false otherwise */ +static inline bool +zap_check_mapping_skip(struct zap_details *details, struct page *page) +{ + if (!details || !page) + return false; + + if (!(details->zap_flags & ZAP_FLAG_CHECK_MAPPING)) + return false; + + return details->zap_mapping !=3D page_rmapping(page); +} + struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long ad= dr, pte_t pte); struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned lon= g addr, diff --git a/mm/memory.c b/mm/memory.c index dd49dea276e3..43d8641dbe18 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1226,16 +1226,8 @@ static unsigned long zap_pte_range(struct mmu_gath= er *tlb, struct page *page; =20 page =3D vm_normal_page(vma, addr, ptent); - if (unlikely(details) && page) { - /* - * unmap_shared_mapping_pages() wants to - * invalidate cache without truncating: - * unmap shared but keep private pages. - */ - if (details->check_mapping && - details->check_mapping !=3D page_rmapping(page)) - continue; - } + if (unlikely(zap_check_mapping_skip(details, page))) + continue; ptent =3D ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); tlb_remove_tlb_entry(tlb, pte, addr); @@ -1267,17 +1259,8 @@ static unsigned long zap_pte_range(struct mmu_gath= er *tlb, if (is_device_private_entry(entry)) { struct page *page =3D device_private_entry_to_page(entry); =20 - if (unlikely(details && details->check_mapping)) { - /* - * unmap_shared_mapping_pages() wants to - * invalidate cache without truncating: - * unmap shared but keep private pages. - */ - if (details->check_mapping !=3D - page_rmapping(page)) - continue; - } - + if (unlikely(zap_check_mapping_skip(details, page))) + continue; pte_clear_not_present_full(mm, addr, pte, tlb->fullmm); rss[mm_counter(page)]--; page_remove_rmap(page, false); @@ -3185,9 +3168,11 @@ void unmap_mapping_pages(struct address_space *map= ping, pgoff_t start, pgoff_t nr, bool even_cows) { pgoff_t first_index =3D start, last_index =3D start + nr - 1; - struct zap_details details =3D { }; + struct zap_details details =3D { .zap_mapping =3D mapping }; + + if (!even_cows) + details.zap_flags |=3D ZAP_FLAG_CHECK_MAPPING; =20 - details.check_mapping =3D even_cows ? NULL : mapping; if (last_index < first_index) last_index =3D ULONG_MAX; =20 --=20 2.26.2