Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753679AbeAKDnH convert rfc822-to-8bit (ORCPT + 1 other); Wed, 10 Jan 2018 22:43:07 -0500 Received: from smtp.h3c.com ([60.191.123.56]:44316 "EHLO h3cmg01-ex.h3c.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753377AbeAKDnG (ORCPT ); Wed, 10 Jan 2018 22:43:06 -0500 From: Changwei Ge To: Gang He , "jlbec@evilplan.org" , "mfasheh@versity.com" CC: "ocfs2-devel@oss.oracle.com" , "linux-kernel@vger.kernel.org" Subject: Re: [Ocfs2-devel] [PATCH v2 2/2] ocfs2: add trimfs lock to avoid duplicated trims in cluster Thread-Topic: [Ocfs2-devel] [PATCH v2 2/2] ocfs2: add trimfs lock to avoid duplicated trims in cluster Thread-Index: AdOJ3PVpr6PIaeXlR1CPvv/Xoq4ERA== Date: Thu, 11 Jan 2018 03:41:22 +0000 Message-ID: <63ADC13FD55D6546B7DECE290D39E373F290EF51@H3CMLB12-EX.srv.huawei-3com.com> References: <1513228484-2084-1-git-send-email-ghe@suse.com> <1513228484-2084-2-git-send-email-ghe@suse.com> <63ADC13FD55D6546B7DECE290D39E373F290E6C5@H3CMLB12-EX.srv.huawei-3com.com> <5A5647C2020000F9000A2929@prv-mh.provo.novell.com> <63ADC13FD55D6546B7DECE290D39E373F290E878@H3CMLB12-EX.srv.huawei-3com.com> <5A5657D8020000F9000A2987@prv-mh.provo.novell.com> <63ADC13FD55D6546B7DECE290D39E373F290E930@H3CMLB12-EX.srv.huawei-3com.com> <5A57372A020000F9000A2E01@prv-mh.provo.novell.com> <63ADC13FD55D6546B7DECE290D39E373F290EED7@H3CMLB12-EX.srv.huawei-3com.com> <5A574B7F020000F9000A2EF7@prv-mh.provo.novell.com> Accept-Language: en-US, zh-CN Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.125.136.231] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On 2018/1/11 11:33, Gang He wrote: > Hi Changwei, > > >>>> >> On 2018/1/11 10:07, Gang He wrote: >>> Hi Changwei, >>> >>> >>>>>> >>>> On 2018/1/10 18:14, Gang He wrote: >>>>> Hi Changwei, >>>>> >>>>> >>>>>>>> >>>>>> On 2018/1/10 17:05, Gang He wrote: >>>>>>> Hi Changwei, >>>>>>> >>>>>>> >>>>>>>>>> >>>>>>>> Hi Gang, >>>>>>>> >>>>>>>> On 2017/12/14 13:16, Gang He wrote: >>>>>>>>> As you know, ocfs2 has support trim the underlying disk via >>>>>>>>> fstrim command. But there is a problem, ocfs2 is a shared disk >>>>>>>>> cluster file system, if the user configures a scheduled fstrim >>>>>>>>> job on each file system node, this will trigger multiple nodes >>>>>>>>> trim a shared disk simultaneously, it is very wasteful for CPU >>>>>>>>> and IO consumption, also might negatively affect the lifetime >>>>>>>>> of poor-quality SSD devices. >>>>>>>>> Then, we introduce a trimfs dlm lock to communicate with each >>>>>>>>> other in this case, which will make only one fstrim command to >>>>>>>>> do the trimming on a shared disk among the cluster, the fstrim >>>>>>>>> commands from the other nodes should wait for the first fstrim >>>>>>>>> to finish and returned success directly, to avoid running a the >>>>>>>>> same trim on the shared disk again. >>>>>>>>> >>>>>>>>> Compare with first version, I change the fstrim commands' returned >>>>>>>>> value and behavior in case which meets a fstrim command is running >>>>>>>>> on a shared disk. >>>>>>>>> >>>>>>>>> Signed-off-by: Gang He >>>>>>>>> --- >>>>>>>>> fs/ocfs2/alloc.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ >>>>>>>>> 1 file changed, 44 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c >>>>>>>>> index ab5105f..5c9c3e2 100644 >>>>>>>>> --- a/fs/ocfs2/alloc.c >>>>>>>>> +++ b/fs/ocfs2/alloc.c >>>>>>>>> @@ -7382,6 +7382,7 @@ int ocfs2_trim_fs(struct super_block *sb, struct >>>>>>>> fstrim_range *range) >>>>>>>>> struct buffer_head *gd_bh = NULL; >>>>>>>>> struct ocfs2_dinode *main_bm; >>>>>>>>> struct ocfs2_group_desc *gd = NULL; >>>>>>>>> + struct ocfs2_trim_fs_info info, *pinfo = NULL; >>>>>>>> >>>>>>>> I think *pinfo* is not necessary. >>>>>>> This pointer is necessary, since it can be NULL or non-NULL depend on the >>>>>> code logic. >>>>>> >>>>>> This point is OK for me. >>>>>> >>>>>>> >>>>>>>>> >>>>>>>>> start = range->start >> osb->s_clustersize_bits; >>>>>>>>> len = range->len >> osb->s_clustersize_bits; >>>>>>>>> @@ -7419,6 +7420,42 @@ int ocfs2_trim_fs(struct super_block *sb, struct >>>>>>>> fstrim_range *range) >>>>>>>>> >>>>>>>>> trace_ocfs2_trim_fs(start, len, minlen); >>>>>>>>> >>>>>>>>> + ocfs2_trim_fs_lock_res_init(osb); >>>>>>>>> + ret = ocfs2_trim_fs_lock(osb, NULL, 1); >>>>>>>> >>>>>>>> I don't get why try to lock here and if fails, acquire the same lock again >>>>>>>> later but wait until granted. >>>>>>> Please think about the user case, the patch is only used to handle this >>>>>> case. >>>>>>> When the administer configures a fstrim schedule task on each node, then >>>>>> each node will trigger a fstrim on shared disks concurrently. >>>>>>> In this case, we should avoid duplicated fstrim on a shared disk since this >>>>>> will waste CPU/IO resources and affect SSD lifetime sometimes. >>>>>> >>>>>> I'm not worrying about that trimfs will affect SSD's lifetime quite a lot, >>>>>> since physical-logical address converting table resides in RAM while SSD is >>>>>> working. >>>>>> And that table won't be at a big scale. My point here is not affecting this >>>>>> patch. Just a tip here. >>>>> This depend on SSD firmware implementation, but for secure-trim, it really >>>> possibly affect SSD lifetime. >>>>> >>>>>>> Firstly, we use try_lock to get fstrim dlm lock to identify if there is any >>>>>> other node which is doing fstrim on the disk. >>>>>>> If not, this node is the first one, this node should do fstrim operation on >>>>>> the disk. >>>>>>> If yes, this node is not the first one, this node should wait until the >>>>>> first node is done for fstrim operation, then return the result from DLM >>>>>> lock's value. >>>>>>> >>>>>>>> Can it just acquire the _trimfs_ lock as a blocking one directly here? >>>>>>> We can not do a blocking lock directly, since we need to identify if there >>>>>> is any other node has being do fstrim operation when this node start to do >>>>>> fstrim. >>>>>> >>>>>> Thanks for your elaboration. >>>>>> >>>>>> Well how about the third node trying to trimming fs too? >>>>>> It needs LVB from the second node. >>>>>> But it seems that the second node can't provide a valid LVB. >>>>>> So the third node will perform trimfs once more. >>>>> No, the second node does not change DLM lock's value, but the DLM lock's >>>> value is still valid. >>>>> The third node also refer to this DLM lock's value, then do the same logic >>>> like the second node. >>>> >>>> Hi Gang, >>>> I don't see any places where ocfs2_lock_res::ocfs2_lock_res_ops::set_lvb is >>>> set while flag LOCK_TYPE_USES_LVB is added. >>>> >>>> Are you sure below code path can work well? >>> Yes, have done a full testing on two and three nodes. >>> >>>> ocfs2_process_blocked_lock >>>> ocfs2_unblock_lock >>>> Reference to ::set_lvb since LOCK_TYPE_USES_LVB is set. >>>> >>> the set_lvb callback function is not necessary, if we update DLM lock value >> by ourselves before unlock. >> >> I think this may relates to *LOCK_TYPE_REQUIRES_REFRESH* flag. > Alright, I think *LOCK_TYPE_REQUIRES_REFRESH* flag is harmless here, although this flag is probably unnecessary. OK, I agree with adding *LOCK_TYPE_REQUIRES_REFRESH* for now. Can you give a explanation for my another concern about three nodes' concurrent trimming fs.? For your convenience, I paste it here: The LVB passing path should be like below: NODE 1 lvb (ex granted at time1) -> NODE 2 lvb(ex granted at time2) -> NODE 3 lvb(ex granted at time3). time1 < time2 < time3 So I think NODE 3 can't obtain LVB from NODE 1 but from NODE 2. Moreover, if node 1 is the master of trimfs lock resource, node 1's LVB will be updated to be the same as node 2. > >> Actually, I don't see why this flag is necessary to _orphan scan_. >> Why can't _orphan scan_ also set LVB during >> ocfs2_process_blocked_lock->ocfs2_unblock_lock? >> >> And it seems that _orphan scan_ also doesn't need to persist any stuff in >> LVB into disk. > More comments, you can look at dlmglue.c file carefully. > set_lvb is a callback function, which will be invoked automatically before downgrade. > you can use this mechanism, you also do not do like that. > you just need to make sure to update DLM lock value before unlock/downgrade. > > Thanks > Gang > >> >> Thanks, >> Changwei >> >>> By the way, the code is transparent to the underlying DLM stack (o2cb or >> pcmk). >> >> True. >>> >>> Thanks >>> Gang >>> >>>> Thanks, >>>> Changwei >>>> >>>>> >>>>>> >>>>>> IOW, three nodes are trying to trimming fs concurrently. Is your patch able >>>>>> to handle such a scenario? >>>>> Yes, the patch can handle this case. >>>>> >>>>>> >>>>>> Even the second lock request with QUEUE set just follows >>>>>> ocfs2_trim_fs_lock_res_uninit() will not get rid of concurrent trimfs. >>>>>> >>>>>>> >>>>>>>> >>>>>>>>> + if (ret < 0) { >>>>>>>>> + if (ret != -EAGAIN) { >>>>>>>>> + mlog_errno(ret); >>>>>>>>> + ocfs2_trim_fs_lock_res_uninit(osb); >>>>>>>>> + goto out_unlock; >>>>>>>>> + } >>>>>>>>> + >>>>>>>>> + mlog(ML_NOTICE, "Wait for trim on device (%s) to " >>>>>>>>> + "finish, which is running from another node.\n", >>>>>>>>> + osb->dev_str); >>>>>>>>> + ret = ocfs2_trim_fs_lock(osb, &info, 0); >>>>>>>>> + if (ret < 0) { >>>>>>>>> + mlog_errno(ret); >>>>>>>>> + ocfs2_trim_fs_lock_res_uninit(osb); >>>>>>>> >>>>>>>> In ocfs2_trim_fs_lock_res_uninit(), you drop lock. But it is never granted. >>>>>>>> Still need to drop lock resource? >>>>>>> Yes, we need to init/uninit fstrim dlm lock resource for each time. >>>>>>> Otherwise, trylock does not work, this is a little different from other dlm >>>>>> lock usage in ocfs2. >>>>>> >>>>>> This point is OK for now, too. >>>>>>> >>>>>>>> >>>>>>>>> + goto out_unlock; >>>>>>>>> + } >>>>>>>>> + >>>>>>>>> + if (info.tf_valid && info.tf_success && >>>>>>>>> + info.tf_start == start && info.tf_len == len && >>>>>>>>> + info.tf_minlen == minlen) { >>>>>>>>> + /* Avoid sending duplicated trim to a shared device */ >>>>>>>>> + mlog(ML_NOTICE, "The same trim on device (%s) was " >>>>>>>>> + "just done from node (%u), return.\n", >>>>>>>>> + osb->dev_str, info.tf_nodenum); >>>>>>>>> + range->len = info.tf_trimlen; >>>>>>>>> + goto out_trimunlock; >>>>>>>>> + } >>>>>>>>> + } >>>>>>>>> + >>>>>>>>> + info.tf_nodenum = osb->node_num; >>>>>>>>> + info.tf_start = start; >>>>>>>>> + info.tf_len = len; >>>>>>>>> + info.tf_minlen = minlen; >>>>>>>> >>>>>>>> If we faild during dong trimfs, I think we should not cache above info in >>>>>>>> LVB. >>>>>>> It is necessary, if the second node is waiting the first node, the first >>>>>> node fails to do fstrim, >>>>>>> the first node should update dlm lock's value, then the second node can get >>>>>> the latest dlm lock value (rather than the last time DLM lock value), >>>>>>> the second node will do the fstrim again, since the first node has failed. >>>>>> >>>>>> Yes, it makes scene. >>>>>>> >>>>>>>> BTW, it seems that this patch is on top of 'try lock' patches which you >>>>>>>> previously sent out. >>>>>>>> Are they related? >>>>>>> try lock patch is related to non-block aio support for ocfs2. >>>>>>> >>>>>>> Thanks >>>>>>> Gang >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Changwei >>>>>>>> >>>>>>>>> + >>>>>>>>> /* Determine first and last group to examine based on start and len */ >>>>>>>>> first_group = ocfs2_which_cluster_group(main_bm_inode, start); >>>>>>>>> if (first_group == osb->first_cluster_group_blkno) >>>>>>>>> @@ -7463,6 +7500,13 @@ int ocfs2_trim_fs(struct super_block *sb, struct >>>>>>>> fstrim_range *range) >>>>>>>>> group += ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg); >>>>>>>>> } >>>>>>>>> range->len = trimmed * sb->s_blocksize; >>>>>>>>> + >>>>>>>>> + info.tf_trimlen = range->len; >>>>>>>>> + info.tf_success = (ret ? 0 : 1); >>>>>>>>> + pinfo = &info; >>>>>>>>> +out_trimunlock: >>>>>>>>> + ocfs2_trim_fs_unlock(osb, pinfo); >>>>>>>>> + ocfs2_trim_fs_lock_res_uninit(osb); >>>>>>>>> out_unlock: >>>>>>>>> ocfs2_inode_unlock(main_bm_inode, 0); >>>>>>>>> brelse(main_bm_bh); >>>>>>>>> >>>>>>> >>>>> >>> >