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[67.231.145.42]) by mx.google.com with ESMTPS id s13si12415808pgn.123.2019.08.07.16.37.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Aug 2019 16:37:41 -0700 (PDT) Received-SPF: pass (google.com: domain of prvs=31225916b7=songliubraving@fb.com designates 67.231.145.42 as permitted sender) client-ip=67.231.145.42; Authentication-Results: mx.google.com; dkim=pass header.i=@fb.com header.s=facebook header.b="J+m5f/t4"; spf=pass (google.com: domain of prvs=31225916b7=songliubraving@fb.com designates 67.231.145.42 as permitted sender) smtp.mailfrom="prvs=31225916b7=songliubraving@fb.com"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=fb.com Received: from pps.filterd (m0044008.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x77NYIRm003950 for ; Wed, 7 Aug 2019 16:37:41 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-type; s=facebook; bh=QCXgQ1j+DyNDDAhgp7fIcjUO5uiv3v51QF0EDrfCLxw=; b=J+m5f/t4QpaD1Wrw+w57zoiiogbQqFA+DYikA89WMmTFzK3vpitmrsmCQkdquggXEV1+ +JyroykUIoO1yXXYS9WXD3BLSKUXgk59E+l+WL4OrDcX+ghbjJj2jR8UidZUdeIsXFw2 lz8Z4vl5Kb0fUbgxwxOp5dQNqBY5R8fBTso= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2u87ueg4sc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 07 Aug 2019 16:37:41 -0700 Received: from mx-out.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Wed, 7 Aug 2019 16:37:39 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 314A762E2D9E; Wed, 7 Aug 2019 16:37:39 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , , CC: , , , , , , Song Liu Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v12 3/6] mm, thp: introduce FOLL_SPLIT_PMD Date: Wed, 7 Aug 2019 16:37:26 -0700 Message-ID: <20190807233729.3899352-4-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190807233729.3899352-1-songliubraving@fb.com> References: <20190807233729.3899352-1-songliubraving@fb.com> X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-07_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908070208 X-FB-Internal: deliver 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: This patches introduces a new foll_flag: FOLL_SPLIT_PMD. As the name says FOLL_SPLIT_PMD splits huge pmd for given mm_struct, the underlining huge page stays as-is. FOLL_SPLIT_PMD is useful for cases where we need to use regular pages, but would switch back to huge page and huge pmd on. One of such example is uprobe. The following patches use FOLL_SPLIT_PMD in uprobe. Cc: Oleg Nesterov Acked-by: Kirill A. Shutemov Signed-off-by: Song Liu --- include/linux/mm.h | 1 + mm/gup.c | 8 ++++++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f189176dabed..74db879711eb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2614,6 +2614,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, #define FOLL_COW 0x4000 /* internal GUP flag */ #define FOLL_ANON 0x8000 /* don't do file mappings */ #define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */ +#define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */ /* * NOTE on FOLL_LONGTERM: diff --git a/mm/gup.c b/mm/gup.c index 98f13ab37bac..c20afe800b3f 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -399,7 +399,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, spin_unlock(ptl); return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); } - if (flags & FOLL_SPLIT) { + if (flags & (FOLL_SPLIT | FOLL_SPLIT_PMD)) { int ret; page = pmd_page(*pmd); if (is_huge_zero_page(page)) { @@ -408,7 +408,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, split_huge_pmd(vma, pmd, address); if (pmd_trans_unstable(pmd)) ret = -EBUSY; - } else { + } else if (flags & FOLL_SPLIT) { if (unlikely(!try_get_page(page))) { spin_unlock(ptl); return ERR_PTR(-ENOMEM); @@ -420,6 +420,10 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, put_page(page); if (pmd_none(*pmd)) return no_page_table(vma, flags); + } else { /* flags & FOLL_SPLIT_PMD */ + spin_unlock(ptl); + split_huge_pmd(vma, pmd, address); + ret = pte_alloc(mm, pmd) ? -ENOMEM : 0; } return ret ? ERR_PTR(ret) : -- 2.17.1