[PATCH RESEND] f2fs: support soft block reservation

[Chao Yu]

From: Yunlong Song <yunlong.song@xxxxxxxxxx>

It supports to extend reserved_blocks sysfs interface to be soft
threshold, which allows user configure it exceeding current available
user space.

Signed-off-by: Yunlong Song <yunlong.song@xxxxxxxxxx>
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 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@xxxxxxxxxx>
 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