This patch allows root to reserve some blocks via mount option.

"-o reserve_root=N" means N x 4KB-sized blocks for root only.

Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---

Change log from v3:
 - fix 0.2% calculation
 - preserve reserve_root=%u from remount_fs

 fs/f2fs/f2fs.h  | 26 ++++++++++++++++++++++----
 fs/f2fs/super.c | 35 ++++++++++++++++++++++++++++++-----
 fs/f2fs/sysfs.c |  3 ++-
 3 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 5f7f42267221..9dde05c62b1c 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -95,6 +95,7 @@ extern char *fault_name[FAULT_MAX];
 #define F2FS_MOUNT_PRJQUOTA            0x00200000
 #define F2FS_MOUNT_QUOTA               0x00400000
 #define F2FS_MOUNT_INLINE_XATTR_SIZE   0x00800000
+#define F2FS_MOUNT_RESERVE_ROOT                0x01000000
 
 #define clear_opt(sbi, option) ((sbi)->mount_opt.opt &= ~F2FS_MOUNT_##option)
 #define set_opt(sbi, option)   ((sbi)->mount_opt.opt |= F2FS_MOUNT_##option)
@@ -1110,6 +1111,7 @@ struct f2fs_sb_info {
        block_t last_valid_block_count;         /* for recovery */
        block_t reserved_blocks;                /* configurable reserved blocks 
*/
        block_t current_reserved_blocks;        /* current reserved blocks */
+       block_t root_reserved_blocks;           /* root reserved blocks */
 
        unsigned int nquota_files;              /* # of quota sysfile */
 
@@ -1562,6 +1564,12 @@ static inline bool f2fs_has_xattr_block(unsigned int ofs)
        return ofs == XATTR_NODE_OFFSET;
 }
 
+static inline block_t reserve_root_limit(struct f2fs_sb_info *sbi)
+{
+       /* limit is 0.2% */
+       return (sbi->user_block_count << 1) / 1000;
+}
+
 static inline void f2fs_i_blocks_write(struct inode *, block_t, bool, bool);
 static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
                                 struct inode *inode, blkcnt_t *count)
@@ -1591,11 +1599,17 @@ static inline int inc_valid_block_count(struct 
f2fs_sb_info *sbi,
        sbi->total_valid_block_count += (block_t)(*count);
        avail_user_block_count = sbi->user_block_count -
                                        sbi->current_reserved_blocks;
+
+       if (!(test_opt(sbi, RESERVE_ROOT) && capable(CAP_SYS_RESOURCE)))
+               avail_user_block_count -= sbi->root_reserved_blocks;
+
        if (unlikely(sbi->total_valid_block_count > avail_user_block_count)) {
                diff = sbi->total_valid_block_count - avail_user_block_count;
+               if (diff > *count)
+                       diff = *count;
                *count -= diff;
                release = diff;
-               sbi->total_valid_block_count = avail_user_block_count;
+               sbi->total_valid_block_count -= diff;
                if (!*count) {
                        spin_unlock(&sbi->stat_lock);
                        percpu_counter_sub(&sbi->alloc_valid_block_count, diff);
@@ -1784,9 +1798,13 @@ 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->current_reserved_blocks >
-                                               sbi->user_block_count)) {
+       valid_block_count = sbi->total_valid_block_count +
+                                       sbi->current_reserved_blocks + 1;
+
+       if (!(test_opt(sbi, RESERVE_ROOT) && capable(CAP_SYS_RESOURCE)))
+               valid_block_count += sbi->root_reserved_blocks;
+
+       if (unlikely(valid_block_count > sbi->user_block_count)) {
                spin_unlock(&sbi->stat_lock);
                goto enospc;
        }
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index cb876d905ca5..3c62492b6a0d 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -107,6 +107,7 @@ enum {
        Opt_noextent_cache,
        Opt_noinline_data,
        Opt_data_flush,
+       Opt_reserve_root,
        Opt_mode,
        Opt_io_size_bits,
        Opt_fault_injection,
@@ -157,6 +158,7 @@ static match_table_t f2fs_tokens = {
        {Opt_noextent_cache, "noextent_cache"},
        {Opt_noinline_data, "noinline_data"},
        {Opt_data_flush, "data_flush"},
+       {Opt_reserve_root, "reserve_root=%u"},
        {Opt_mode, "mode=%s"},
        {Opt_io_size_bits, "io_bits=%u"},
        {Opt_fault_injection, "fault_injection=%u"},
@@ -488,6 +490,18 @@ static int parse_options(struct super_block *sb, char 
*options)
                case Opt_data_flush:
                        set_opt(sbi, DATA_FLUSH);
                        break;
+               case Opt_reserve_root:
+                       if (args->from && match_int(args, &arg))
+                               return -EINVAL;
+                       if (test_opt(sbi, RESERVE_ROOT)) {
+                               f2fs_msg(sb, KERN_INFO,
+                                       "Preserve previous reserve_root=%u",
+                                       sbi->root_reserved_blocks);
+                       } else {
+                               sbi->root_reserved_blocks = arg;
+                               set_opt(sbi, RESERVE_ROOT);
+                       }
+                       break;
                case Opt_mode:
                        name = match_strdup(&args[0]);
 
@@ -994,21 +1008,22 @@ static int f2fs_statfs(struct dentry *dentry, struct 
kstatfs *buf)
        struct super_block *sb = dentry->d_sb;
        struct f2fs_sb_info *sbi = F2FS_SB(sb);
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
-       block_t total_count, user_block_count, start_count, ovp_count;
+       block_t total_count, user_block_count, start_count;
        u64 avail_node_count;
 
        total_count = le64_to_cpu(sbi->raw_super->block_count);
        user_block_count = sbi->user_block_count;
        start_count = le32_to_cpu(sbi->raw_super->segment0_blkaddr);
-       ovp_count = SM_I(sbi)->ovp_segments << sbi->log_blocks_per_seg;
        buf->f_type = F2FS_SUPER_MAGIC;
        buf->f_bsize = sbi->blocksize;
 
        buf->f_blocks = total_count - start_count;
-       buf->f_bfree = user_block_count - valid_user_blocks(sbi) + ovp_count;
+       buf->f_bfree = user_block_count - valid_user_blocks(sbi) -
+                                               sbi->current_reserved_blocks +
+                                               sbi->root_reserved_blocks;
        buf->f_bavail = user_block_count - valid_user_blocks(sbi) -
-                                               sbi->current_reserved_blocks;
-
+                                               sbi->current_reserved_blocks -
+                                               sbi->root_reserved_blocks;
        avail_node_count = sbi->total_node_count - sbi->nquota_files -
                                                F2FS_RESERVED_NODE_NUM;
 
@@ -1136,6 +1151,9 @@ static int f2fs_show_options(struct seq_file *seq, struct 
dentry *root)
        else if (test_opt(sbi, LFS))
                seq_puts(seq, "lfs");
        seq_printf(seq, ",active_logs=%u", sbi->active_logs);
+       if (test_opt(sbi, RESERVE_ROOT))
+               seq_printf(seq, ",reserve_root=%u",
+                               sbi->root_reserved_blocks);
        if (F2FS_IO_SIZE_BITS(sbi))
                seq_printf(seq, ",io_size=%uKB", F2FS_IO_SIZE_KB(sbi));
 #ifdef CONFIG_F2FS_FAULT_INJECTION
@@ -2571,6 +2589,13 @@ static int f2fs_fill_super(struct super_block *sb, void 
*data, int silent)
        sbi->reserved_blocks = 0;
        sbi->current_reserved_blocks = 0;
 
+       if (test_opt(sbi, RESERVE_ROOT) &&
+               sbi->root_reserved_blocks > reserve_root_limit(sbi)) {
+               sbi->root_reserved_blocks = reserve_root_limit(sbi);
+               f2fs_msg(sb, KERN_INFO,
+                       "Reduce reserved blocks for root = %u\n",
+                               sbi->root_reserved_blocks);
+       }
        for (i = 0; i < NR_INODE_TYPE; i++) {
                INIT_LIST_HEAD(&sbi->inode_list[i]);
                spin_lock_init(&sbi->inode_lock[i]);
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 7e15cbc5b8e1..41887e6ec1b3 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -162,7 +162,8 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 #endif
        if (a->struct_type == RESERVED_BLOCKS) {
                spin_lock(&sbi->stat_lock);
-               if (t > (unsigned long)sbi->user_block_count) {
+               if (t > (unsigned long)(sbi->user_block_count -
+                                       sbi->root_reserved_blocks)) {
                        spin_unlock(&sbi->stat_lock);
                        return -EINVAL;
                }
-- 
2.15.0.531.g2ccb3012c9-goog

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