It renames reserved_blocks sysfs interface to target_reserved_blocks,
and supports to extend it to be soft threshold, which allows user
configure it exceeding current available user space. So this patch
also introduces a new sysfs interface called current_reserved_blocks to
show the current blocks which have already been reserved.

Signed-off-by: Yunlong Song <yunlong.s...@huawei.com>
Signed-off-by: Chao Yu <yuch...@huawei.com>
---
 Documentation/ABI/testing/sysfs-fs-f2fs | 15 +++++++++++++--
 fs/f2fs/f2fs.h                          | 15 ++++++++++++---
 fs/f2fs/super.c                         |  5 +++--
 fs/f2fs/sysfs.c                         | 20 +++++++++++++++-----
 4 files changed, 43 insertions(+), 12 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs 
b/Documentation/ABI/testing/sysfs-fs-f2fs
index 11b7f4e..482d78b 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -134,11 +134,22 @@ Contact:  "Sheng Yong" <shengyo...@huawei.com>
 Description:
                 Controls the injection type.
 
-What:          /sys/fs/f2fs/<disk>/reserved_blocks
+What:          /sys/fs/f2fs/<disk>/target_reserved_blocks
 Date:          June 2017
 Contact:       "Chao Yu" <yuch...@huawei.com>
 Description:
-                Controls current reserved blocks in system.
+                Controls target reserved blocks in system, the threshold
+                is soft, it could exceed current available user space.
+
+What:          /sys/fs/f2fs/<disk>/current_reserved_blocks
+Date:          October 2017
+Contact:       "Yunlong Song" <yunlong.s...@huawei.com>
+Contact:       "Chao Yu" <yuch...@huawei.com>
+Description:
+                Shows current reserved blocks in system, it may be temporarily
+                smaller than target_reserved_blocks, but will gradually
+                increase to target_reserved_blocks when more free blocks are
+                freed by user later.
 
 What:          /sys/fs/f2fs/<disk>/gc_urgent
 Date:          August 2017
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 13a96b8..c26fccb 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1081,7 +1081,8 @@ struct f2fs_sb_info {
        block_t total_valid_block_count;        /* # of valid blocks */
        block_t discard_blks;                   /* discard command candidats */
        block_t last_valid_block_count;         /* for recovery */
-       block_t reserved_blocks;                /* configurable reserved blocks 
*/
+       block_t target_reserved_blocks;         /* configurable reserved blocks 
*/
+       block_t current_reserved_blocks;        /* current reserved blocks */
 
        u32 s_next_generation;                  /* for NFS support */
 
@@ -1557,7 +1558,8 @@ 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;
@@ -1591,6 +1593,10 @@ 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->target_reserved_blocks &&
+               sbi->current_reserved_blocks < sbi->target_reserved_blocks)
+               sbi->current_reserved_blocks = min(sbi->target_reserved_blocks,
+                                       sbi->current_reserved_blocks + count);
        spin_unlock(&sbi->stat_lock);
        f2fs_i_blocks_write(inode, count, false, true);
 }
@@ -1737,7 +1743,7 @@ 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;
@@ -1780,6 +1786,9 @@ static inline void dec_valid_node_count(struct 
f2fs_sb_info *sbi,
 
        sbi->total_valid_node_count--;
        sbi->total_valid_block_count--;
+       if (sbi->target_reserved_blocks &&
+               sbi->current_reserved_blocks < sbi->target_reserved_blocks)
+               sbi->current_reserved_blocks++;
 
        spin_unlock(&sbi->stat_lock);
 
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 213d2c1..c682978 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -987,7 +987,7 @@ 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;
 
@@ -2457,7 +2457,8 @@ static int f2fs_fill_super(struct super_block *sb, void 
*data, int silent)
        sbi->total_valid_block_count =
                                le64_to_cpu(sbi->ckpt->valid_block_count);
        sbi->last_valid_block_count = sbi->total_valid_block_count;
-       sbi->reserved_blocks = 0;
+       sbi->target_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 e09e59c..568e32f 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -30,7 +30,7 @@ enum {
        FAULT_INFO_RATE,        /* struct f2fs_fault_info */
        FAULT_INFO_TYPE,        /* struct f2fs_fault_info */
 #endif
-       RESERVED_BLOCKS,
+       RESERVED_BLOCKS,        /* struct f2fs_sb_info */
 };
 
 struct f2fs_attr {
@@ -114,6 +114,12 @@ static ssize_t features_show(struct f2fs_attr *a,
        return len;
 }
 
+static ssize_t current_reserved_blocks_show(struct f2fs_attr *a,
+                                       struct f2fs_sb_info *sbi, char *buf)
+{
+       return snprintf(buf, PAGE_SIZE, "%u\n", sbi->current_reserved_blocks);
+}
+
 static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
                        struct f2fs_sb_info *sbi, char *buf)
 {
@@ -153,12 +159,13 @@ 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->target_reserved_blocks,
+                               sbi->user_block_count - valid_user_blocks(sbi));
                spin_unlock(&sbi->stat_lock);
                return count;
        }
@@ -272,7 +279,8 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, reclaim_segments, rec_prefree_segments);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, max_small_discards, max_discards);
 F2FS_RW_ATTR(DCC_INFO, discard_cmd_control, discard_granularity, 
discard_granularity);
-F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, reserved_blocks, reserved_blocks);
+F2FS_RW_ATTR(RESERVED_BLOCKS, f2fs_sb_info, target_reserved_blocks,
+                                                       target_reserved_blocks);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, batched_trim_sections, trim_sections);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, ipu_policy, ipu_policy);
 F2FS_RW_ATTR(SM_INFO, f2fs_sm_info, min_ipu_util, min_ipu_util);
@@ -293,6 +301,7 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
 F2FS_GENERAL_RO_ATTR(dirty_segments);
 F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
 F2FS_GENERAL_RO_ATTR(features);
+F2FS_GENERAL_RO_ATTR(current_reserved_blocks);
 
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 F2FS_FEATURE_RO_ATTR(encryption, FEAT_CRYPTO);
@@ -337,7 +346,8 @@ static ssize_t f2fs_feature_show(struct f2fs_attr *a,
        ATTR_LIST(dirty_segments),
        ATTR_LIST(lifetime_write_kbytes),
        ATTR_LIST(features),
-       ATTR_LIST(reserved_blocks),
+       ATTR_LIST(target_reserved_blocks),
+       ATTR_LIST(current_reserved_blocks),
        NULL,
 };
 
-- 
1.8.5.2

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