From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx48CnmbXlcQYioZTFAvkcEoD2UTm0FuZDzLWrl2W0f+1LGvgcXX5EFSOQBFe45BG4RMyKi/5 ARC-Seal: i=1; a=rsa-sha256; t=1522168548; cv=none; d=google.com; s=arc-20160816; b=DCVrC/xNbzVfsWubFrYeMNSoFjNZZiRemPLRBTQJ2hkNfT9X6YOw5TVs6lpct6Zjyf U+wAcuQlVhucZw87SQzfXiCazDv33Fdg762aXOs1thiIwrE4lnIagF8v3aAn2L2n9t7p P3uGcJVwt0nj8uEBM44DUkg6SCxMZN9nGnHdOb4TETZrXWz0mDPHt8zOn8En+Eji24dS VFeSJfIbO+Ec2PJ9omf62Y9/Bq58L/MR80BfocsZ5rZ7U5FGPXTcyIKMoiUwTqs+89Tf Q1HGlgcOkqBfQYJ/iCJxbjX9gskbxNqBimGWkWKPeFMsElyVJYtOe3VP/WGrBamy8Mzn w0hg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=jp81KnXk541V0C6/jcSQoDzvGhxvPSGBRW3kP7/6KRc=; b=F5RjtlmusEtgfTOLIDu3sWmPr8D1DqGUbeMtqlphlLHd8YFQklXPitdTwy7kx5tDSF r/xxJB3j2rrQBSL/TcvfbpzqEMaiStMkxpUSfsZ057KEVOppP9G4v288GRDcMYM2oQLv JyiwmDtgnJ8rCBgCq2/m5f1OWk2qcM0J/BYMVxqYwr3jsnBy+lZfTAJZeKGV87xf2uWF rFYE20FfQy28tNlHKn4P0Tny3sG1LHbpy6HtuURgDjxqWqw+pDXzmQFioDbHsf9m35OK w0+CVfv4DeRqAdBlO6b2c5OVaMw7mu7laa1SwXp/Zx90j6yOrQ1YzWqea1O254fXWBxv Rt+g== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Kirill A. Shutemov" , Laura Abbott , Jerome Marchand , Vlastimil Babka , Andrew Morton , Linus Torvalds Subject: [PATCH 4.14 049/101] mm/khugepaged.c: convert VM_BUG_ON() to collapse fail Date: Tue, 27 Mar 2018 18:27:21 +0200 Message-Id: <20180327162753.037315086@linuxfoundation.org> X-Mailer: git-send-email 2.16.3 In-Reply-To: <20180327162749.993880276@linuxfoundation.org> References: <20180327162749.993880276@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1596109134052943557?= X-GMAIL-MSGID: =?utf-8?q?1596109408053950414?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kirill A. Shutemov commit fece2029a9e65b9a990831afe2a2b83290cbbe26 upstream. khugepaged is not yet able to convert PTE-mapped huge pages back to PMD mapped. We do not collapse such pages. See check khugepaged_scan_pmd(). But if between khugepaged_scan_pmd() and __collapse_huge_page_isolate() somebody managed to instantiate THP in the range and then split the PMD back to PTEs we would have a problem -- VM_BUG_ON_PAGE(PageCompound(page)) will get triggered. It's possible since we drop mmap_sem during collapse to re-take for write. Replace the VM_BUG_ON() with graceful collapse fail. Link: http://lkml.kernel.org/r/20180315152353.27989-1-kirill.shutemov@linux.intel.com Fixes: b1caa957ae6d ("khugepaged: ignore pmd tables with THP mapped with ptes") Signed-off-by: Kirill A. Shutemov Cc: Laura Abbott Cc: Jerome Marchand Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/khugepaged.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -530,7 +530,12 @@ static int __collapse_huge_page_isolate( goto out; } - VM_BUG_ON_PAGE(PageCompound(page), page); + /* TODO: teach khugepaged to collapse THP mapped with pte */ + if (PageCompound(page)) { + result = SCAN_PAGE_COMPOUND; + goto out; + } + VM_BUG_ON_PAGE(!PageAnon(page), page); /*