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bh=Z+qQSwZU5O6LoNzg+Y0KcgzyFROGp1piGCQLbieshoU=; b=Fl6MNm9YhWAC35q4yRQMYFdTAKRNhljX8wcvRVfdbWwXYutitKbnaOh5P/+DUDshyOTCxB Xd+uz+EN+ul9YciGxhN8QNenLkY77kGYB53Gx6F+TkfXRIsDe1X9fw/qJWRov31VBu6zeu T/a6dbsY23gk70OfMsYfoT7v3J8p+ng= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-18-4zJ54y7iMkaiv39wEbMctA-1; Wed, 13 Sep 2023 08:51:27 -0400 X-MC-Unique: 4zJ54y7iMkaiv39wEbMctA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6E9678011AD; Wed, 13 Sep 2023 12:51:27 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.39.193.225]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1F56421B20B1; Wed, 13 Sep 2023 12:51:26 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Mike Kravetz , Muchun Song Subject: [PATCH v1 5/6] mm/rmap: simplify PageAnonExclusive sanity checks when adding anon rmap Date: Wed, 13 Sep 2023 14:51:12 +0200 Message-ID: <20230913125113.313322-6-david@redhat.com> In-Reply-To: <20230913125113.313322-1-david@redhat.com> References: <20230913125113.313322-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B79DB1C0037 X-Stat-Signature: yyc1a186mjid1yjz9g7n8g8hmpgtrkio X-Rspam-User: X-HE-Tag: 1694609491-38975 X-HE-Meta: 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 +AyvBdfi atdtYilhrfSwUq4EHkE0+u4iWzb9MjKVr7P9f0olkwE4SQj6FKNZN4OKnVbkhbUXPfRK8BZSSDQ4UAjFqwKG90YAYYAJHFU5U3wlO05tWvk/gleYsUsqrgU00N7yWCHQNs1NDU19BpTz18rZTggPzbMNvHD5Rw1+wuJIMnbAZFp0pmLI= 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: Let's sanity-check PageAnonExclusive vs. mapcount in page_add_anon_rmap() and hugepage_add_anon_rmap() after setting PageAnonExclusive simply by re-reading the mapcounts. We can stop initializing the "first" variable in page_add_anon_rmap() and no longer need an atomic_inc_and_test() in hugepage_add_anon_rmap(). While at it, switch to VM_WARN_ON_FOLIO(). Signed-off-by: David Hildenbrand Reported-by: syzbot+6e4f59235036c3c2e296@syzkaller.appspotmail.com Signed-off-by: David Hildenbrand --- mm/rmap.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 489c142d073b..10d477a0991f 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1199,7 +1199,7 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, atomic_t *mapped = &folio->_nr_pages_mapped; int nr = 0, nr_pmdmapped = 0; bool compound = flags & RMAP_COMPOUND; - bool first = true; + bool first; /* Is page being mapped by PTE? Is this its first map to be added? */ if (likely(!compound)) { @@ -1228,9 +1228,6 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, } } - VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); - VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page); - if (nr_pmdmapped) __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped); if (nr) @@ -1252,6 +1249,8 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, } if (flags & RMAP_EXCLUSIVE) SetPageAnonExclusive(page); + VM_WARN_ON_FOLIO(page_mapcount(page) > 1 && PageAnonExclusive(page), + folio); mlock_vma_folio(folio, vma, compound); } @@ -2532,15 +2531,14 @@ void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address, rmap_t flags) { struct folio *folio = page_folio(page); - int first; VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); - first = atomic_inc_and_test(&folio->_entire_mapcount); - VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); - VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page); + atomic_inc(&folio->_entire_mapcount); if (flags & RMAP_EXCLUSIVE) SetPageAnonExclusive(page); + VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 && + PageAnonExclusive(page), folio); } void hugepage_add_new_anon_rmap(struct folio *folio,