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Thu, 7 May 2020 00:44:37 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 30t1r95cpc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 07 May 2020 00:44:37 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0470iX0S026145; Thu, 7 May 2020 00:44:34 GMT Received: from ayz-linux.localdomain (/68.7.158.207) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 06 May 2020 17:44:33 -0700 From: Anthony Yznaga To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: willy@infradead.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, rppt@linux.ibm.com, akpm@linux-foundation.org, hughd@google.com, ebiederm@xmission.com, masahiroy@kernel.org, ardb@kernel.org, ndesaulniers@google.com, dima@golovin.in, daniel.kiper@oracle.com, nivedita@alum.mit.edu, rafael.j.wysocki@intel.com, dan.j.williams@intel.com, zhenzhong.duan@oracle.com, jroedel@suse.de, bhe@redhat.com, guro@fb.com, Thomas.Lendacky@amd.com, andriy.shevchenko@linux.intel.com, keescook@chromium.org, hannes@cmpxchg.org, minchan@kernel.org, mhocko@kernel.org, ying.huang@intel.com, yang.shi@linux.alibaba.com, gustavo@embeddedor.com, ziqian.lzq@antfin.com, vdavydov.dev@gmail.com, jason.zeng@intel.com, kevin.tian@intel.com, zhiyuan.lv@intel.com, lei.l.li@intel.com, paul.c.lai@intel.com, ashok.raj@intel.com, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org Subject: [RFC 33/43] PKRAM: atomically add and remove link pages Date: Wed, 6 May 2020 17:41:59 -0700 Message-Id: <1588812129-8596-34-git-send-email-anthony.yznaga@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1588812129-8596-1-git-send-email-anthony.yznaga@oracle.com> References: <1588812129-8596-1-git-send-email-anthony.yznaga@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9613 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0 suspectscore=0 spamscore=0 mlxlogscore=999 malwarescore=0 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005070001 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9613 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 clxscore=1015 suspectscore=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005070001 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: Add and remove pkram_link pages from a pkram_obj atomically to prepare for multithreading. Signed-off-by: Anthony Yznaga --- mm/pkram.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/mm/pkram.c b/mm/pkram.c index 5f4e4d12865f..042c14dedc25 100644 --- a/mm/pkram.c +++ b/mm/pkram.c @@ -551,22 +551,31 @@ static void pkram_truncate(void) static void pkram_add_link(struct pkram_link *link, struct pkram_obj *obj) { - link->link_pfn = obj->link_pfn; - obj->link_pfn = page_to_pfn(virt_to_page(link)); + __u64 link_pfn = page_to_pfn(virt_to_page(link)); + __u64 *head = &obj->link_pfn; + + do { + link->link_pfn = *head; + } while (cmpxchg64(head, link->link_pfn, link_pfn) != link->link_pfn); } static struct pkram_link *pkram_remove_link(struct pkram_obj *obj) { struct pkram_link *current_link; + __u64 *head = &obj->link_pfn; + __u64 head_pfn = *head; + + while (head_pfn) { + current_link = pfn_to_kaddr(head_pfn); + if (cmpxchg64(head, head_pfn, current_link->link_pfn) == head_pfn) { + current_link->link_pfn = 0; + return current_link; + } - if (!obj->link_pfn) - return NULL; - - current_link = pfn_to_kaddr(obj->link_pfn); - obj->link_pfn = current_link->link_pfn; - current_link->link_pfn = 0; + head_pfn = *head; + } - return current_link; + return NULL; } static void pkram_stream_init(struct pkram_stream *ps,