On 10/26, Chao Yu wrote:
> From: Yunlong Song <yunlong.s...@huawei.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?

What does current_reserved_blocks mean? Isn't "reserved_blocks" current?
We have to make sysfs entry show just one value without any string.

Thanks,

> 
> Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
> Signed-off-by: Chao Yu <yuch...@huawei.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" <yuch...@huawei.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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