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Thu, 20 Feb 2020 06:54:39 -0800 (PST) Received: from xz-x1.redhat.com ([104.156.64.75]) by smtp.gmail.com with ESMTPSA id v82sm1725109qka.51.2020.02.20.06.54.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Feb 2020 06:54:38 -0800 (PST) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Martin Cracauer , Mike Rapoport , Hugh Dickins , Jerome Glisse , peterx@redhat.com, "Kirill A . Shutemov" , Matthew Wilcox , Pavel Emelyanov , Brian Geffon , Maya Gokhale , Denis Plotnikov , Andrea Arcangeli , Johannes Weiner , "Dr . David Alan Gilbert" , Linus Torvalds , Mike Kravetz , Marty McFadden , David Hildenbrand , Bobby Powers , Mel Gorman Subject: [PATCH v6 02/16] mm/gup: Fix __get_user_pages() on fault retry of hugetlb Date: Thu, 20 Feb 2020 09:54:18 -0500 Message-Id: <20200220145432.4561-3-peterx@redhat.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200220145432.4561-1-peterx@redhat.com> References: <20200220145432.4561-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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: When follow_hugetlb_page() returns with *locked==0, it means we've got a VM_FAULT_RETRY within the fauling process and we've released the mmap_sem. When that happens, we should stop and bail out. Signed-off-by: Peter Xu --- mm/gup.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 1b4411bd0042..76cb420c0fb7 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -849,6 +849,16 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, i = follow_hugetlb_page(mm, vma, pages, vmas, &start, &nr_pages, i, gup_flags, locked); + if (locked && *locked == 0) { + /* + * We've got a VM_FAULT_RETRY + * and we've lost mmap_sem. + * We must stop here. + */ + BUG_ON(gup_flags & FOLL_NOWAIT); + BUG_ON(ret != 0); + goto out; + } continue; } }