Message-ID: <58a75537-d7ff-1e9b-8b4b-86b78935ae62@huawei.com>
Date:   Fri, 11 Aug 2017 18:18:25 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Yunlong Song <yunlong.song@...wei.com>, <jaegeuk@...nel.org>,
        <chao@...nel.org>, <yunlong.song@...oud.com>
CC:     <miaoxie@...wei.com>, <bintian.wang@...wei.com>,
        <linux-fsdevel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: introduce cur_reserved_blocks in sysfs

On 2017/8/10 19:41, Yunlong Song wrote:
> It may block the system in such case, but so does the hard version 
> design. In the hard version,

We'd better not let soft/hard reserved_blocks to eat all left free space, at
least needs to leave enough space for supporting system's activation.

Thanks,

> when reserve_blocks is set to the value = user_block_count - 
> total_valid_block_count, then
> the user free space can also drop to zero and has the same problem. IMO, 
> kernel does not need
> to take this responsibility, it's android's responsibility.
> 
> On 2017/8/10 19:26, Chao Yu wrote:
>> On 2017/8/10 11:58, Yunlong Song wrote:
>>> I think the aim of reserved_blocks function is to leave space for f2fs
>>> and FTL, so I change it to a
>>> soft version so that it can be used to fit to the data image which does
>>> not satisfy the hard version,
>>> especially for backward compatibility when updated kernel with new
>>> default reserved_blocks set
>>> (currently it is initially set 0 as default, but can be set any value
>>> with my new patch).
>>>
>>> As for the uid/gid, does current f2fs space management design consider
>>> this issue? IMO, I think we
>> Upper layer application has considered this issue, as when free space touchs the
>> threshold, system will block any operation and give a hint to clean up user's
>> data. So w/o uid/gid reserved block, it will be OK. But for your requirement,
>> user free space will drop to zero, and before current reserved block number
>> touch soft reserved block limitation, user can only do deletion, so in this
>> time, if any system/service flow depends on file creation, could result in
>> blocking the system.
>>
>>> can just ensure the reserved space for file system no matter user/system
>>> type. Whether the value of
>>> reserved_blocks is OK or not, should not be filesystem's issue.
>>> Filesystem just provide this interface,
>>> and the upper layer, such as android vold should take care of the value
>>> of reserved_blocks and make
>>> sure its value is appropriate and will not block any activation of
>>> system user, if it really happens, android
>>> should change the value dynamically, it is fine, since we make
>>> reserved_blocks to a soft version.
>> We can not make sure in strategy changing flow, there is no file creation
>> dependence. Even if we can, if the reserved_blocks is not appropriate, why not
>> setting it correctly before?
>>
>> Thanks,
>>
>>> On 2017/8/10 11:15, Chao Yu wrote:
>>>> On 2017/8/8 21:43, Yunlong Song wrote:
>>>>> In this patch, we add a new sysfs interface, we can use it to gradually achieve
>>>>> the reserved_blocks finally, even when reserved_blocks is initially set over
>>>>> user_block_count - total_valid_block_count. This is very useful, especially when
>>>>> we upgrade kernel with new reserved_blocks value, but old disk image unluckily has
>>>>> user_block_count - total_valid_block_count smaller than the desired reserved_blocks.
>>>>> With this patch, f2fs can try its best to reserve space and get close to the
>>>>> reserved_blocks, and the current value of achieved reserved_blocks can be shown
>>>>> in real time.
>>>> Oh, this looks like a soft limitation in quota system, but original
>>>> reserved_blocks implementation likes a hard one, so this patch changes the
>>>> semantics of reserved_blocks.
>>>>
>>>> Actually, I doubt that it would be hard to reserve all left free space in real
>>>> user scenario now, since system user's activation may depend on free space of
>>>> data partition due to file creation requirement, so w/o supporting feature of
>>>> uid/gid reserved block, soft reservation will block any activation of system
>>>> user, such as android.
>>>>
>>>> Thanks,
>>>>
>>>>> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>>>> ---
>>>>>    Documentation/ABI/testing/sysfs-fs-f2fs |  6 ++++++
>>>>>    fs/f2fs/f2fs.h                          |  9 +++++++--
>>>>>    fs/f2fs/super.c                         |  4 +++-
>>>>>    fs/f2fs/sysfs.c                         | 15 ++++++++++-----
>>>>>    4 files changed, 26 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> index 11b7f4e..bdbb9f3 100644
>>>>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>>>>> @@ -151,3 +151,9 @@ Date:		August 2017
>>>>>    Contact:	"Jaegeuk Kim" <jaegeuk@...nel.org>
>>>>>    Description:
>>>>>    		 Controls sleep time of GC urgent mode
>>>>> +
>>>>> +What:		/sys/fs/f2fs/<disk>/cur_reserved_blocks
>>>>> +Date:		August 2017
>>>>> +Contact:	"Yunlong Song" <yunlong.song@...wei.com>
>>>>> +Description:
>>>>> +		 Shows current reserved blocks in system.
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index cea329f..3b7056f 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -1040,6 +1040,7 @@ 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 cur_reserved_blocks;		/* current reserved blocks */
>>>>>    
>>>>>    	u32 s_next_generation;			/* for NFS support */
>>>>>    
>>>>> @@ -1514,7 +1515,7 @@ 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->cur_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;
>>>>> @@ -1548,6 +1549,8 @@ 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;
>>>>> +	sbi->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>>> +									sbi->cur_reserved_blocks + count);
>>>>>    	spin_unlock(&sbi->stat_lock);
>>>>>    	f2fs_i_blocks_write(inode, count, false, true);
>>>>>    }
>>>>> @@ -1694,7 +1697,7 @@ 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->cur_reserved_blocks >
>>>>>    						sbi->user_block_count)) {
>>>>>    		spin_unlock(&sbi->stat_lock);
>>>>>    		goto enospc;
>>>>> @@ -1737,6 +1740,8 @@ static inline void dec_valid_node_count(struct f2fs_sb_info *sbi,
>>>>>    
>>>>>    	sbi->total_valid_node_count--;
>>>>>    	sbi->total_valid_block_count--;
>>>>> +	sbi->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>>> +									sbi->cur_reserved_blocks + 1);
>>>>>    
>>>>>    	spin_unlock(&sbi->stat_lock);
>>>>>    
>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>> index 4c1bdcb..2934aa2 100644
>>>>> --- a/fs/f2fs/super.c
>>>>> +++ b/fs/f2fs/super.c
>>>>> @@ -957,7 +957,7 @@ 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->cur_reserved_blocks;
>>>>>    
>>>>>    	avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
>>>>>    
>>>>> @@ -2411,6 +2411,8 @@ 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->cur_reserved_blocks = min(sbi->reserved_blocks,
>>>>> +						sbi->user_block_count - sbi->total_valid_block_count);
>>>>>    
>>>>>    	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 b769a3d..405c13f 100644
>>>>> --- a/fs/f2fs/sysfs.c
>>>>> +++ b/fs/f2fs/sysfs.c
>>>>> @@ -76,6 +76,12 @@ static ssize_t lifetime_write_kbytes_show(struct f2fs_attr *a,
>>>>>    			BD_PART_WRITTEN(sbi)));
>>>>>    }
>>>>>    
>>>>> +static ssize_t cur_reserved_blocks_show(struct f2fs_attr *a,
>>>>> +		struct f2fs_sb_info *sbi, char *buf)
>>>>> +{
>>>>> +	return snprintf(buf, PAGE_SIZE, "%u\n", sbi->cur_reserved_blocks);
>>>>> +}
>>>>> +
>>>>>    static ssize_t features_show(struct f2fs_attr *a,
>>>>>    		struct f2fs_sb_info *sbi, char *buf)
>>>>>    {
>>>>> @@ -143,12 +149,9 @@ 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) {
>>>>> -			spin_unlock(&sbi->stat_lock);
>>>>> -			return -EINVAL;
>>>>> -		}
>>>>>    		*ui = t;
>>>>> +		sbi->cur_reserved_blocks = min(t, sbi->user_block_count -
>>>>> +										sbi->total_valid_block_count);
>>>>>    		spin_unlock(&sbi->stat_lock);
>>>>>    		return count;
>>>>>    	}
>>>>> @@ -274,6 +277,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
>>>>>    #endif
>>>>>    F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
>>>>>    F2FS_GENERAL_RO_ATTR(features);
>>>>> +F2FS_GENERAL_RO_ATTR(cur_reserved_blocks);
>>>>>    
>>>>>    #ifdef CONFIG_F2FS_FS_ENCRYPTION
>>>>>    F2FS_FEATURE_RO_ATTR(encryption, FEAT_CRYPTO);
>>>>> @@ -317,6 +321,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
>>>>>    	ATTR_LIST(lifetime_write_kbytes),
>>>>>    	ATTR_LIST(features),
>>>>>    	ATTR_LIST(reserved_blocks),
>>>>> +	ATTR_LIST(cur_reserved_blocks),
>>>>>    	NULL,
>>>>>    };
>>>>>    
>>>>>
>>>> .
>>>>
>>
>> .
>>
> 

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