1 files changed, 81 insertions, 3 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 968ca93..6fea87d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -81,6 +81,7 @@ static int ext4_feature_set_ok(struct super_block *sb, int readonly);
 static void ext4_destroy_lazyinit_thread(void);
 static void ext4_unregister_li_request(struct super_block *sb);
 static void ext4_clear_request_list(void);
+static int ext4_reserve_clusters(struct ext4_sb_info *, ext4_fsblk_t);
 
 #if !defined(CONFIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
 static struct file_system_type ext2_fs_type = {
@@ -2382,6 +2383,17 @@ struct ext4_attr {
 	int offset;
 };
 
+static int parse_strtoull(const char *buf,
+		unsigned long long max, unsigned long long *value)
+{
+	int ret;
+
+	ret = kstrtoull(skip_spaces(buf), 0, value);
+	if (!ret && *value > max)
+		ret = -EINVAL;
+	return ret;
+}
+
 static int parse_strtoul(const char *buf,
 		unsigned long max, unsigned long *value)
 {
@@ -2466,6 +2478,27 @@ static ssize_t sbi_ui_store(struct ext4_attr *a,
 	return count;
 }
 
+static ssize_t reserved_clusters_show(struct ext4_attr *a,
+				  struct ext4_sb_info *sbi, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%llu\n",
+		(unsigned long long) atomic64_read(&sbi->s_resv_clusters));
+}
+
+static ssize_t reserved_clusters_store(struct ext4_attr *a,
+				   struct ext4_sb_info *sbi,
+				   const char *buf, size_t count)
+{
+	unsigned long long val;
+	int ret;
+
+	if (parse_strtoull(buf, -1ULL, &val))
+		return -EINVAL;
+	ret = ext4_reserve_clusters(sbi, val);
+
+	return ret ? ret : count;
+}
+
 static ssize_t trigger_test_error(struct ext4_attr *a,
 				  struct ext4_sb_info *sbi,
 				  const char *buf, size_t count)
@@ -2503,6 +2536,7 @@ static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
 EXT4_RO_ATTR(delayed_allocation_blocks);
 EXT4_RO_ATTR(session_write_kbytes);
 EXT4_RO_ATTR(lifetime_write_kbytes);
+EXT4_RW_ATTR(reserved_clusters);
 EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
 		 inode_readahead_blks_store, s_inode_readahead_blks);
 EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
@@ -2520,6 +2554,7 @@ static struct attribute *ext4_attrs[] = {
 	ATTR_LIST(delayed_allocation_blocks),
 	ATTR_LIST(session_write_kbytes),
 	ATTR_LIST(lifetime_write_kbytes),
+	ATTR_LIST(reserved_clusters),
 	ATTR_LIST(inode_readahead_blks),
 	ATTR_LIST(inode_goal),
 	ATTR_LIST(mb_stats),
@@ -3195,6 +3230,40 @@ int ext4_calculate_overhead(struct super_block *sb)
 	return 0;
 }
 
+
+static ext4_fsblk_t ext4_calculate_resv_clusters(struct ext4_sb_info *sbi)
+{
+	ext4_fsblk_t resv_clusters;
+
+	/*
+	 * By default we reserve 2% or 4096 clusters, whichever is smaller.
+	 * This should cover the situations where we can not afford to run
+	 * out of space like for example punch hole, or converting
+	 * uninitialized extents in delalloc path. In most cases such
+	 * allocation would require 1, or 2 blocks, higher numbers are
+	 * very rare.
+	 */
+	resv_clusters = ext4_blocks_count(sbi->s_es) >> sbi->s_cluster_bits;
+
+	do_div(resv_clusters, 50);
+	resv_clusters = min_t(ext4_fsblk_t, resv_clusters, 4096);
+
+	return resv_clusters;
+}
+
+
+static int ext4_reserve_clusters(struct ext4_sb_info *sbi, ext4_fsblk_t count)
+{
+	ext4_fsblk_t clusters = ext4_blocks_count(sbi->s_es) >>
+				sbi->s_cluster_bits;
+
+	if (count >= clusters)
+		return -EINVAL;
+
+	atomic64_set(&sbi->s_resv_clusters, count);
+	return 0;
+}
+
 static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 {
 	char *orig_data = kstrdup(data, GFP_KERNEL);
@@ -3918,6 +3987,13 @@ no_journal:
 			 "available");
 	}
 
+	err = ext4_reserve_clusters(sbi, ext4_calculate_resv_clusters(sbi));
+	if (err) {
+		ext4_msg(sb, KERN_ERR, "failed to reserve %llu clusters for "
+			 "reserved pool", ext4_calculate_resv_clusters(sbi));
+		goto failed_mount4a;
+	}
+
 	err = ext4_setup_system_zone(sb);
 	if (err) {
 		ext4_msg(sb, KERN_ERR, "failed to initialize system "
@@ -4750,9 +4826,10 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
 	struct super_block *sb = dentry->d_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
-	ext4_fsblk_t overhead = 0;
+	ext4_fsblk_t overhead = 0, resv_blocks;
 	u64 fsid;
 	s64 bfree;
+	resv_blocks = EXT4_C2B(sbi, atomic64_read(&sbi->s_resv_clusters));
 
 	if (!test_opt(sb, MINIX_DF))
 		overhead = sbi->s_overhead;
@@ -4764,8 +4841,9 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
 		percpu_counter_sum_positive(&sbi->s_dirtyclusters_counter);
 	/* prevent underflow in case that few free space is available */
 	buf->f_bfree = EXT4_C2B(sbi, max_t(s64, bfree, 0));
-	buf->f_bavail = buf->f_bfree - ext4_r_blocks_count(es);
-	if (buf->f_bfree < ext4_r_blocks_count(es))
+	buf->f_bavail = buf->f_bfree -
+			(ext4_r_blocks_count(es) + resv_blocks);
+	if (buf->f_bfree < (ext4_r_blocks_count(es) + resv_blocks))
 		buf->f_bavail = 0;
 	buf->f_files = le32_to_cpu(es->s_inodes_count);
 	buf->f_ffree = percpu_counter_sum_positive(&sbi->s_freeinodes_counter);