Re: [PATCH] f2fs: introduce cur_reserved_blocks in sysfs

[Chao Yu]

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@xxxxxxxxxx>
> ---
>  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@xxxxxxxxxx>
>  Description:
>  		 Controls sleep time of GC urgent mode
> +
> +What:		/sys/fs/f2fs/<disk>/cur_reserved_blocks
> +Date:		August 2017
> +Contact:	"Yunlong Song" <yunlong.song@xxxxxxxxxx>
> +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,
>  };
>  
>