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Date:   Thu, 26 Oct 2017 16:44:04 +0200
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
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 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
user deletes some files, can we update current_reserved_blocks automatically?
We're able to update it in dev_valid_blocks(), as I guess.

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

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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