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Date:   Tue, 15 Jan 2019 08:00:36 +0000
From:   Changwei Ge <ge.changwei@....com>
To:     Gang He <ghe@...e.com>, "jlbec@...lplan.org" <jlbec@...lplan.org>,
        "mark@...heh.com" <mark@...heh.com>,
        "jiangqi903@...il.com" <jiangqi903@...il.com>
CC:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Ocfs2-devel] [PATCH] ocfs2: fix the application IO timeout
 when fstrim is running

On 2019/1/15 13:49, Gang He wrote:
> Hello Changewei,
> 
>>>> On 2019/1/15 at 11:50, in message
> <63ADC13FD55D6546B7DECE290D39E3730127825EFD@...MLB12-EX.srv.huawei-3com.com>,
> Changwei Ge <ge.changwei@....com> wrote:
>> Hi Gang,
>>
>> Most parts of this patch look sane to me, just a tiny question...
>>
>> On 2019/1/11 17:01, Gang He wrote:
>>> The user reported this problem, the upper application IO was
>>> timeout when fstrim was running on this ocfs2 partition. the
>>> application monitoring resource agent considered that this
>>> application did not work, then this node was fenced by the cluster
>>> brain (e.g. pacemaker).
>>> The root cause is that fstrim thread always holds main_bm meta-file
>>> related locks until all the cluster groups are trimmed.
>>> This patch will make fstrim thread release main_bm meta-file
>>> related locks when each cluster group is trimmed, this will let
>>> the current application IO has a chance to claim the clusters from
>>> main_bm meta-file.
>>>
>>> Signed-off-by: Gang He <ghe@...e.com>
>>> ---
>>>    fs/ocfs2/alloc.c       | 159 +++++++++++++++++++++++++----------------
>>>    fs/ocfs2/dlmglue.c     |   5 ++
>>>    fs/ocfs2/ocfs2.h       |   1 +
>>>    fs/ocfs2/ocfs2_trace.h |   2 +
>>>    fs/ocfs2/super.c       |   2 +
>>>    5 files changed, 106 insertions(+), 63 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
>>> index d1cbb27808e2..6f0999015a44 100644
>>> --- a/fs/ocfs2/alloc.c
>>> +++ b/fs/ocfs2/alloc.c
>>> @@ -7532,10 +7532,11 @@ static int ocfs2_trim_group(struct super_block *sb,
>>>    	return count;
>>>    }
>>>    
>>> -int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
>>> +static
>>> +int ocfs2_trim_mainbm(struct super_block *sb, struct fstrim_range *range)
>>>    {
>>>    	struct ocfs2_super *osb = OCFS2_SB(sb);
>>> -	u64 start, len, trimmed, first_group, last_group, group;
>>> +	u64 start, len, trimmed = 0, first_group, last_group = 0, group = 0;
>>>    	int ret, cnt;
>>>    	u32 first_bit, last_bit, minlen;
>>>    	struct buffer_head *main_bm_bh = NULL;
>>> @@ -7543,7 +7544,6 @@ 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;
>>>    
>>>    	start = range->start >> osb->s_clustersize_bits;
>>>    	len = range->len >> osb->s_clustersize_bits;
>>> @@ -7552,6 +7552,9 @@ int ocfs2_trim_fs(struct super_block *sb, struct
>> fstrim_range *range)
>>>    	if (minlen >= osb->bitmap_cpg || range->len < sb->s_blocksize)
>>>    		return -EINVAL;
>>>    
>>> +	trace_ocfs2_trim_mainbm(start, len, minlen);
>>> +
>>> +next_group:
>>>    	main_bm_inode = ocfs2_get_system_file_inode(osb,
>>>    						    GLOBAL_BITMAP_SYSTEM_INODE,
>>>    						    OCFS2_INVALID_SLOT);
>>> @@ -7570,64 +7573,34 @@ int ocfs2_trim_fs(struct super_block *sb, struct
>> fstrim_range *range)
>>>    	}
>>>    	main_bm = (struct ocfs2_dinode *)main_bm_bh->b_data;
>>>    
>>> -	if (start >= le32_to_cpu(main_bm->i_clusters)) {
>>> -		ret = -EINVAL;
>>> -		goto out_unlock;
>>> -	}
>>> -
>>> -	len = range->len >> osb->s_clustersize_bits;
>>> -	if (start + len > le32_to_cpu(main_bm->i_clusters))
>>> -		len = le32_to_cpu(main_bm->i_clusters) - start;
>>> -
>>> -	trace_ocfs2_trim_fs(start, len, minlen);
>>> -
>>> -	ocfs2_trim_fs_lock_res_init(osb);
>>> -	ret = ocfs2_trim_fs_lock(osb, NULL, 1);
>>> -	if (ret < 0) {
>>> -		if (ret != -EAGAIN) {
>>> -			mlog_errno(ret);
>>> -			ocfs2_trim_fs_lock_res_uninit(osb);
>>> +	/*
>>> +	 * Do some check before trim the first group.
>>> +	 */
>>> +	if (!group) {
>>> +		if (start >= le32_to_cpu(main_bm->i_clusters)) {
>>> +			ret = -EINVAL;
>>>    			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);
>>> -			goto out_unlock;
>>> -		}
>>> +		if (start + len > le32_to_cpu(main_bm->i_clusters))
>>> +			len = le32_to_cpu(main_bm->i_clusters) - start;
>>>    
>>> -		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;
>>> -		}
>>> +		/*
>>> +		 * 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)
>>> +			first_bit = start;
>>> +		else
>>> +			first_bit = start - ocfs2_blocks_to_clusters(sb,
>>> +								first_group);
>>> +		last_group = ocfs2_which_cluster_group(main_bm_inode,
>>> +						       start + len - 1);
>>> +		group = first_group;
>>>    	}
>>>    
>>> -	info.tf_nodenum = osb->node_num;
>>> -	info.tf_start = start;
>>> -	info.tf_len = len;
>>> -	info.tf_minlen = minlen;
>>> -
>>> -	/* 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)
>>> -		first_bit = start;
>>> -	else
>>> -		first_bit = start - ocfs2_blocks_to_clusters(sb, first_group);
>>> -	last_group = ocfs2_which_cluster_group(main_bm_inode, start + len - 1);
>>> -	last_bit = osb->bitmap_cpg;
>>> -
>>> -	trimmed = 0;
>>> -	for (group = first_group; group <= last_group;) {
>>> +	do {
>>>    		if (first_bit + len >= osb->bitmap_cpg)
>>>    			last_bit = osb->bitmap_cpg;
>>>    		else
>>> @@ -7659,21 +7632,81 @@ int ocfs2_trim_fs(struct super_block *sb, struct
>> fstrim_range *range)
>>>    			group = ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
>>>    		else
>>>    			group += ocfs2_clusters_to_blocks(sb, osb->bitmap_cpg);
>>> -	}
>>> -	range->len = trimmed * sb->s_blocksize;
>>> +	} while (0);
>>>    
>>> -	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);
>>> +	main_bm_bh = NULL;
>>>    out_mutex:
>>>    	inode_unlock(main_bm_inode);
>>>    	iput(main_bm_inode);
>>> +
>>> +	/*
>>> +	 * If all the groups trim are not done or failed, but we should release
>>> +	 * main_bm related locks for avoiding the current IO starve, then go to
>>> +	 * trim the next group
>>> +	 */
>>> +	if (ret >= 0 && group <= last_group)
>>> +		goto next_group;
>>>    out:
>>> +	range->len = trimmed * sb->s_blocksize;
>>> +	return ret;
>>> +}
>>> +
>>> +int ocfs2_trim_fs(struct super_block *sb, struct fstrim_range *range)
>>> +{
>>> +	int ret;
>>> +	struct ocfs2_super *osb = OCFS2_SB(sb);
>>> +	struct ocfs2_trim_fs_info info, *pinfo = NULL;
>>> +
>>> +	ocfs2_trim_fs_lock_res_init(osb);
>>> +
>>> +	trace_ocfs2_trim_fs(range->start, range->len, range->minlen);
>>> +
>>> +	ret = ocfs2_trim_fs_lock(osb, NULL, 1);
>>> +	if (ret < 0) {
>>> +		if (ret != -EAGAIN) {
>>> +			mlog_errno(ret);
>>> +			ocfs2_trim_fs_lock_res_uninit(osb);
>>> +			return ret;
>>> +		}
>>> +
>>> +		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);
>>> +			return ret;
>>> +		}
>>> +
>>> +		if (info.tf_valid && info.tf_success &&
>>> +		    info.tf_start == range->start &&
>>> +		    info.tf_len == range->len &&
>>> +		    info.tf_minlen == range->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;
>>> +		}
>>> +	}
>>> +
>>> +	info.tf_nodenum = osb->node_num;
>>> +	info.tf_start = range->start;
>>> +	info.tf_len = range->len;
>>> +	info.tf_minlen = range->minlen;
>>> +
>>> +	ret = ocfs2_trim_mainbm(sb, range);
>>> +
>>> +	info.tf_trimlen = range->len;
>>> +	info.tf_success = (ret < 0 ? 0 : 1);
>>> +	pinfo = &info;
>>> +out:
>>> +	ocfs2_trim_fs_unlock(osb, pinfo);
>>> +	ocfs2_trim_fs_lock_res_uninit(osb);
>>>    	return ret;
>>>    }
>>> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
>>> index 7c835824247e..af405586c5b1 100644
>>> --- a/fs/ocfs2/dlmglue.c
>>> +++ b/fs/ocfs2/dlmglue.c
>>> @@ -686,6 +686,9 @@ void ocfs2_trim_fs_lock_res_init(struct ocfs2_super *osb)
>>>    {
>>>    	struct ocfs2_lock_res *lockres = &osb->osb_trim_fs_lockres;
>>>    
>>> +	/* Only one trimfs thread are allowed to work at the same time. */
>>> +	mutex_lock(&osb->obs_trim_fs_mutex);
>>> +
>>
>> Cluster lock of fstrim have a trylock behavior, will it be better if we
>> trylock here?
> Here, I prefer to just serialize fstrim threads on the local node to simplify the code logic,
> maybe the user want to do like that, although this behavior is not recommended.
> You know, on one node, ideally, the user should call  fstrim command once regularly.
> If he calls fstrim command more times in a very short time,
> the code will not make each fstrim command return to failure, just do the fstrim task one by one.

I have a thought having nothing to do with your patch.
Do you think it's possible for us to implement *discard on unlink file* like ext4 does.
So the application doesn't have to invoke fstrim periodically.

Thanks,
Changwei

> 
> Thanks
> Gang
> 
>>
>> Thanks,
>> Changwei
>>
>>>    	ocfs2_lock_res_init_once(lockres);
>>>    	ocfs2_build_lock_name(OCFS2_LOCK_TYPE_TRIM_FS, 0, 0, lockres->l_name);
>>>    	ocfs2_lock_res_init_common(osb, lockres, OCFS2_LOCK_TYPE_TRIM_FS,
>>> @@ -698,6 +701,8 @@ void ocfs2_trim_fs_lock_res_uninit(struct ocfs2_super
>> *osb)
>>>    
>>>    	ocfs2_simple_drop_lockres(osb, lockres);
>>>    	ocfs2_lock_res_free(lockres);
>>> +
>>> +	mutex_unlock(&osb->obs_trim_fs_mutex);
>>>    }
>>>    
>>>    static void ocfs2_orphan_scan_lock_res_init(struct ocfs2_lock_res *res,
>>> diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
>>> index 4f86ac0027b5..1f029fbe8b8d 100644
>>> --- a/fs/ocfs2/ocfs2.h
>>> +++ b/fs/ocfs2/ocfs2.h
>>> @@ -407,6 +407,7 @@ struct ocfs2_super
>>>    	struct ocfs2_lock_res osb_rename_lockres;
>>>    	struct ocfs2_lock_res osb_nfs_sync_lockres;
>>>    	struct ocfs2_lock_res osb_trim_fs_lockres;
>>> +	struct mutex obs_trim_fs_mutex;
>>>    	struct ocfs2_dlm_debug *osb_dlm_debug;
>>>    
>>>    	struct dentry *osb_debug_root;
>>> diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h
>>> index 2ee76a90ba8f..dc4bce1649c1 100644
>>> --- a/fs/ocfs2/ocfs2_trace.h
>>> +++ b/fs/ocfs2/ocfs2_trace.h
>>> @@ -712,6 +712,8 @@ TRACE_EVENT(ocfs2_trim_extent,
>>>    
>>>    DEFINE_OCFS2_ULL_UINT_UINT_UINT_EVENT(ocfs2_trim_group);
>>>    
>>> +DEFINE_OCFS2_ULL_ULL_ULL_EVENT(ocfs2_trim_mainbm);
>>> +
>>>    DEFINE_OCFS2_ULL_ULL_ULL_EVENT(ocfs2_trim_fs);
>>>    
>>>    /* End of trace events for fs/ocfs2/alloc.c. */
>>> diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
>>> index 3415e0b09398..96ae7cedd487 100644
>>> --- a/fs/ocfs2/super.c
>>> +++ b/fs/ocfs2/super.c
>>> @@ -1847,6 +1847,8 @@ static int ocfs2_mount_volume(struct super_block *sb)
>>>    	if (ocfs2_is_hard_readonly(osb))
>>>    		goto leave;
>>>    
>>> +	mutex_init(&osb->obs_trim_fs_mutex);
>>> +
>>>    	status = ocfs2_dlm_init(osb);
>>>    	if (status < 0) {
>>>    		mlog_errno(status);
>>>
> 

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