f2fs: expose extension_list sysfs entry

This patch adds a sysfs entry 'extension_list' to support
query/add/del item in extension list.

Query:
cat /sys/fs/f2fs/<device>/extension_list

Add:
echo 'extension' > /sys/fs/f2fs/<device>/extension_list

Del:
echo '!extension' > /sys/fs/f2fs/<device>/extension_list

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/sysfs.c

@@ -136,6 +136,18 @@ static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
 	if (!ptr)
 		return -EINVAL;
 
+	if (!strcmp(a->attr.name, "extension_list")) {
+		__u8 (*extlist)[F2FS_EXTENSION_LEN] =
+					sbi->raw_super->extension_list;
+		int count = le32_to_cpu(sbi->raw_super->extension_count);
+		int len = 0, i;
+
+		for (i = 0; i < count; i++)
+			len += snprintf(buf + len, PAGE_SIZE - len, "%s\n",
+								extlist[i]);
+		return len;
+	}
+
 	ui = (unsigned int *)(ptr + a->offset);
 
 	return snprintf(buf, PAGE_SIZE, "%u\n", *ui);
@@ -154,6 +166,32 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 	if (!ptr)
 		return -EINVAL;
 
+	if (!strcmp(a->attr.name, "extension_list")) {
+		const char *name = strim((char *)buf);
+		bool set = true;
+
+		if (name[0] == '!') {
+			name++;
+			set = false;
+		}
+
+		if (strlen(name) >= F2FS_EXTENSION_LEN)
+			return -EINVAL;
+
+		down_write(&sbi->sb_lock);
+
+		ret = update_extension_list(sbi, name, set);
+		if (ret)
+			goto out;
+
+		ret = f2fs_commit_super(sbi, false);
+		if (ret)
+			update_extension_list(sbi, name, !set);
+out:
+		up_write(&sbi->sb_lock);
+		return ret ? ret : count;
+	}
+
 	ui = (unsigned int *)(ptr + a->offset);
 
 	ret = kstrtoul(skip_spaces(buf), 0, &t);
@@ -307,6 +345,7 @@ F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, idle_interval, interval_time[REQ_TIME]);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, iostat_enable, iostat_enable);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, readdir_ra, readdir_ra);
 F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_pin_file_thresh, gc_pin_file_threshold);
+F2FS_RW_ATTR(F2FS_SBI, f2fs_super_block, extension_list, extension_list);
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 F2FS_RW_ATTR(FAULT_INFO_RATE, f2fs_fault_info, inject_rate, inject_rate);
 F2FS_RW_ATTR(FAULT_INFO_TYPE, f2fs_fault_info, inject_type, inject_type);
@@ -357,6 +396,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(iostat_enable),
 	ATTR_LIST(readdir_ra),
 	ATTR_LIST(gc_pin_file_thresh),
+	ATTR_LIST(extension_list),
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 	ATTR_LIST(inject_rate),
 	ATTR_LIST(inject_type),