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Date:   Fri, 27 Oct 2017 10:44:40 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        Yunlong Song <yunlong.song@...wei.com>
Subject: Re: [PATCH RESEND] f2fs: support soft block reservation

On 2017/10/26 22:44, Jaegeuk Kim wrote:
> On 10/26, Chao Yu wrote:
>> On 2017/10/26 17:07, Jaegeuk Kim wrote:
>>> On 10/26, Chao Yu wrote:
>>>> From: Yunlong Song <yunlong.song@...wei.com>
>>>>
>>>> It supports to extend reserved_blocks sysfs interface to be soft
>>>> threshold, which allows user configure it exceeding current available
>>>> user space.
>>>
>>> So, how can we change sbi->reserved_blocks?
>>> Could you please summarize how reserved_blocks and current_reserved_blocks
>>> are different?
>>
>> Okay, let me explain this:
>>
>> Previously, we just support hard reservation of blocks, it means if system
>> has 200MB free blocks, we only can reserve <= 200MB free blocks through sysfs,
>> otherwise, reserving will fail.
>>
>> In this patch, we begin to support soft one, it can reserve blocks exceeding
>> free blocks, which means, if system has 200MB free blocks, we can reserve >
>> 200MB free blocks.
>>>
>>> What does current_reserved_blocks mean? Isn't "reserved_blocks" current?
>>
>> So, reserved_blocks means the target block number we want to reserve, and
>> current_reserved_blocks is current block number we have reserved. Meanwhile
>> blocks are freed by user, we will reserve more free blocks until
>> current_reserved_blocks touching the target reserved_blocks.
> 
> So, what about target_reserved_blocks and current_reserved_blocks? Then, after

Better. :)

> user deletes some files, can we update current_reserved_blocks automatically?
> We're able to update it in dev_valid_blocks(), as I guess.

Yup.

> 
> Please update the description in the patch, and use two sysfs entries to change
> each of values.

OK, let me update this patch.

Thanks,

> 
> Thanks,
> 
>>
>>> We have to make sysfs entry show just one value without any string.
>>
>> For better analysis? So we need another sysfs entry for current_reserved_blocks
>> if we can support this feature?
>>
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>> ---
>>>>  Documentation/ABI/testing/sysfs-fs-f2fs |  3 ++-
>>>>  fs/f2fs/f2fs.h                          | 13 +++++++++++--
>>>>  fs/f2fs/super.c                         |  3 ++-
>>>>  fs/f2fs/sysfs.c                         | 16 ++++++++++++++--
>>>>  4 files changed, 29 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> index 11b7f4ebea7c..ba282ca5eb15 100644
>>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>> @@ -138,7 +138,8 @@ What:		/sys/fs/f2fs/<disk>/reserved_blocks
>>>>  Date:		June 2017
>>>>  Contact:	"Chao Yu" <yuchao0@...wei.com>
>>>>  Description:
>>>> -		 Controls current reserved blocks in system.
>>>> +		 Controls current reserved blocks in system, the threshold
>>>> +		 is soft, it could exceed current available user space.
>>>>  
>>>>  What:		/sys/fs/f2fs/<disk>/gc_urgent
>>>>  Date:		August 2017
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index 6d2984abc50f..6680da47fb1a 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -1094,6 +1094,7 @@ struct f2fs_sb_info {
>>>>  	block_t discard_blks;			/* discard command candidats */
>>>>  	block_t last_valid_block_count;		/* for recovery */
>>>>  	block_t reserved_blocks;		/* configurable reserved blocks */
>>>> +	block_t current_reserved_blocks;	/* current reserved blocks */
>>>>  
>>>>  	u32 s_next_generation;			/* for NFS support */
>>>>  
>>>> @@ -1575,7 +1576,8 @@ static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
>>>>  
>>>>  	spin_lock(&sbi->stat_lock);
>>>>  	sbi->total_valid_block_count += (block_t)(*count);
>>>> -	avail_user_block_count = sbi->user_block_count - sbi->reserved_blocks;
>>>> +	avail_user_block_count = sbi->user_block_count -
>>>> +					sbi->current_reserved_blocks;
>>>>  	if (unlikely(sbi->total_valid_block_count > avail_user_block_count)) {
>>>>  		diff = sbi->total_valid_block_count - avail_user_block_count;
>>>>  		*count -= diff;
>>>> @@ -1609,6 +1611,10 @@ static inline void dec_valid_block_count(struct f2fs_sb_info *sbi,
>>>>  	f2fs_bug_on(sbi, sbi->total_valid_block_count < (block_t) count);
>>>>  	f2fs_bug_on(sbi, inode->i_blocks < sectors);
>>>>  	sbi->total_valid_block_count -= (block_t)count;
>>>> +	if (sbi->reserved_blocks &&
>>>> +		sbi->current_reserved_blocks < sbi->reserved_blocks)
>>>> +		sbi->current_reserved_blocks = min(sbi->reserved_blocks,
>>>> +					sbi->current_reserved_blocks + count);
>>>>  	spin_unlock(&sbi->stat_lock);
>>>>  	f2fs_i_blocks_write(inode, count, false, true);
>>>>  }
>>>> @@ -1755,7 +1761,7 @@ static inline int inc_valid_node_count(struct f2fs_sb_info *sbi,
>>>>  	spin_lock(&sbi->stat_lock);
>>>>  
>>>>  	valid_block_count = sbi->total_valid_block_count + 1;
>>>> -	if (unlikely(valid_block_count + sbi->reserved_blocks >
>>>> +	if (unlikely(valid_block_count + sbi->current_reserved_blocks >
>>>>  						sbi->user_block_count)) {
>>>>  		spin_unlock(&sbi->stat_lock);
>>>>  		goto enospc;
>>>> @@ -1798,6 +1804,9 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,
>>>>  
>>>>  	sbi->total_valid_node_count--;
>>>>  	sbi->total_valid_block_count--;
>>>> +	if (sbi->reserved_blocks &&
>>>> +		sbi->current_reserved_blocks < sbi->reserved_blocks)
>>>> +		sbi->current_reserved_blocks++;
>>>>  
>>>>  	spin_unlock(&sbi->stat_lock);
>>>>  
>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>> index 3fd62ee53eb7..3fd846ac7268 100644
>>>> --- a/fs/f2fs/super.c
>>>> +++ b/fs/f2fs/super.c
>>>> @@ -983,7 +983,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
>>>>  	buf->f_blocks = total_count - start_count;
>>>>  	buf->f_bfree = user_block_count - valid_user_blocks(sbi) + ovp_count;
>>>>  	buf->f_bavail = user_block_count - valid_user_blocks(sbi) -
>>>> -						sbi->reserved_blocks;
>>>> +						sbi->current_reserved_blocks;
>>>>  
>>>>  	avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
>>>>  
>>>> @@ -2450,6 +2450,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>  				le64_to_cpu(sbi->ckpt->valid_block_count);
>>>>  	sbi->last_valid_block_count = sbi->total_valid_block_count;
>>>>  	sbi->reserved_blocks = 0;
>>>> +	sbi->current_reserved_blocks = 0;
>>>>  
>>>>  	for (i = 0; i < NR_INODE_TYPE; i++) {
>>>>  		INIT_LIST_HEAD(&sbi->inode_list[i]);
>>>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>>>> index 751964da2bca..87487ca8f62e 100644
>>>> --- a/fs/f2fs/sysfs.c
>>>> +++ b/fs/f2fs/sysfs.c
>>>> @@ -107,12 +107,23 @@ static ssize_t features_show(struct f2fs_attr *a,
>>>>  	return len;
>>>>  }
>>>>  
>>>> +static ssize_t f2fs_reserved_blocks_show(struct f2fs_attr *a,
>>>> +					struct f2fs_sb_info *sbi, char *buf)
>>>> +{
>>>> +	return snprintf(buf, PAGE_SIZE,
>>>> +			"expected:	%u\ncurrent:	%u\n",
>>>> +			sbi->reserved_blocks, sbi->current_reserved_blocks);
>>>> +}
>>>> +
>>>>  static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
>>>>  			struct f2fs_sb_info *sbi, char *buf)
>>>>  {
>>>>  	unsigned char *ptr = NULL;
>>>>  	unsigned int *ui;
>>>>  
>>>> +	if (a->struct_type == RESERVED_BLOCKS)
>>>> +		return f2fs_reserved_blocks_show(a, sbi, buf);
>>>> +
>>>>  	ptr = __struct_ptr(sbi, a->struct_type);
>>>>  	if (!ptr)
>>>>  		return -EINVAL;
>>>> @@ -146,12 +157,13 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
>>>>  #endif
>>>>  	if (a->struct_type == RESERVED_BLOCKS) {
>>>>  		spin_lock(&sbi->stat_lock);
>>>> -		if ((unsigned long)sbi->total_valid_block_count + t >
>>>> -				(unsigned long)sbi->user_block_count) {
>>>> +		if (t > (unsigned long)sbi->user_block_count) {
>>>>  			spin_unlock(&sbi->stat_lock);
>>>>  			return -EINVAL;
>>>>  		}
>>>>  		*ui = t;
>>>> +		sbi->current_reserved_blocks = min(sbi->reserved_blocks,
>>>> +				sbi->user_block_count - valid_user_blocks(sbi));
>>>>  		spin_unlock(&sbi->stat_lock);
>>>>  		return count;
>>>>  	}
>>>> -- 
>>>> 2.13.1.388.g69e6b9b4f4a9
>>>
>>> .
>>>
> 
> .
> 

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