f2fs: expose features to sysfs entry

This patch exposes what features are supported by current f2fs build to sysfs
entry via:

/sys/fs/f2fs/features/
/sys/fs/f2fs/dev/features
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/sysfs.c

@@ -18,7 +18,6 @@
 #include "gc.h"
 
 static struct proc_dir_entry *f2fs_proc_root;
-static struct kset *f2fs_kset;
 
 /* Sysfs support for f2fs */
 enum {
@@ -41,6 +40,7 @@ struct f2fs_attr {
 			 const char *, size_t);
 	int struct_type;
 	int offset;
+	int id;
 };
 
 static unsigned char *__struct_ptr(struct f2fs_sb_info *sbi, int struct_type)
@@ -76,6 +76,34 @@ static ssize_t lifetime_write_kbytes_show(struct f2fs_attr *a,
 			BD_PART_WRITTEN(sbi)));
 }
 
+static ssize_t features_show(struct f2fs_attr *a,
+		struct f2fs_sb_info *sbi, char *buf)
+{
+	struct super_block *sb = sbi->sb;
+	int len = 0;
+
+	if (!sb->s_bdev->bd_part)
+		return snprintf(buf, PAGE_SIZE, "0\n");
+
+	if (f2fs_sb_has_crypto(sb))
+		len += snprintf(buf, PAGE_SIZE - len, "%s",
+						"encryption");
+	if (f2fs_sb_mounted_blkzoned(sb))
+		len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
+				len ? ", " : "", "blkzoned");
+	if (f2fs_sb_has_extra_attr(sb))
+		len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
+				len ? ", " : "", "extra_attr");
+	if (f2fs_sb_has_project_quota(sb))
+		len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
+				len ? ", " : "", "projquota");
+	if (f2fs_sb_has_inode_chksum(sb))
+		len += snprintf(buf + len, PAGE_SIZE - len, "%s%s",
+				len ? ", " : "", "inode_checksum");
+	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
+	return len;
+}
+
 static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
 			struct f2fs_sb_info *sbi, char *buf)
 {
@@ -155,6 +183,30 @@ static void f2fs_sb_release(struct kobject *kobj)
 	complete(&sbi->s_kobj_unregister);
 }
 
+enum feat_id {
+	FEAT_CRYPTO = 0,
+	FEAT_BLKZONED,
+	FEAT_ATOMIC_WRITE,
+	FEAT_EXTRA_ATTR,
+	FEAT_PROJECT_QUOTA,
+	FEAT_INODE_CHECKSUM,
+};
+
+static ssize_t f2fs_feature_show(struct f2fs_attr *a,
+		struct f2fs_sb_info *sbi, char *buf)
+{
+	switch (a->id) {
+	case FEAT_CRYPTO:
+	case FEAT_BLKZONED:
+	case FEAT_ATOMIC_WRITE:
+	case FEAT_EXTRA_ATTR:
+	case FEAT_PROJECT_QUOTA:
+	case FEAT_INODE_CHECKSUM:
+		return snprintf(buf, PAGE_SIZE, "supported\n");
+	}
+	return 0;
+}
+
 #define F2FS_ATTR_OFFSET(_struct_type, _name, _mode, _show, _store, _offset) \
 static struct f2fs_attr f2fs_attr_##_name = {			\
 	.attr = {.name = __stringify(_name), .mode = _mode },	\
@@ -172,6 +224,13 @@ static struct f2fs_attr f2fs_attr_##_name = {			\
 #define F2FS_GENERAL_RO_ATTR(name) \
 static struct f2fs_attr f2fs_attr_##name = __ATTR(name, 0444, name##_show, NULL)
 
+#define F2FS_FEATURE_RO_ATTR(_name, _id)			\
+static struct f2fs_attr f2fs_attr_##_name = {			\
+	.attr = {.name = __stringify(_name), .mode = 0444 },	\
+	.show	= f2fs_feature_show,				\
+	.id	= _id,						\
+}
+
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_min_sleep_time, min_sleep_time);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_max_sleep_time, max_sleep_time);
 F2FS_RW_ATTR(GC_THREAD, f2fs_gc_kthread, gc_no_gc_sleep_time, no_gc_sleep_time);
@@ -196,6 +255,18 @@ 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);
 #endif
 F2FS_GENERAL_RO_ATTR(lifetime_write_kbytes);
+F2FS_GENERAL_RO_ATTR(features);
+
+#ifdef CONFIG_F2FS_FS_ENCRYPTION
+F2FS_FEATURE_RO_ATTR(encryption, FEAT_CRYPTO);
+#endif
+#ifdef CONFIG_BLK_DEV_ZONED
+F2FS_FEATURE_RO_ATTR(block_zoned, FEAT_BLKZONED);
+#endif
+F2FS_FEATURE_RO_ATTR(atomic_write, FEAT_ATOMIC_WRITE);
+F2FS_FEATURE_RO_ATTR(extra_attr, FEAT_EXTRA_ATTR);
+F2FS_FEATURE_RO_ATTR(project_quota, FEAT_PROJECT_QUOTA);
+F2FS_FEATURE_RO_ATTR(inode_checksum, FEAT_INODE_CHECKSUM);
 
 #define ATTR_LIST(name) (&f2fs_attr_##name.attr)
 static struct attribute *f2fs_attrs[] = {
@@ -222,21 +293,53 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(inject_type),
 #endif
 	ATTR_LIST(lifetime_write_kbytes),
+	ATTR_LIST(features),
 	ATTR_LIST(reserved_blocks),
 	NULL,
 };
 
+static struct attribute *f2fs_feat_attrs[] = {
+#ifdef CONFIG_F2FS_FS_ENCRYPTION
+	ATTR_LIST(encryption),
+#endif
+#ifdef CONFIG_BLK_DEV_ZONED
+	ATTR_LIST(block_zoned),
+#endif
+	ATTR_LIST(atomic_write),
+	ATTR_LIST(extra_attr),
+	ATTR_LIST(project_quota),
+	ATTR_LIST(inode_checksum),
+	NULL,
+};
+
 static const struct sysfs_ops f2fs_attr_ops = {
 	.show	= f2fs_attr_show,
 	.store	= f2fs_attr_store,
 };
 
-static struct kobj_type f2fs_ktype = {
+static struct kobj_type f2fs_sb_ktype = {
 	.default_attrs	= f2fs_attrs,
 	.sysfs_ops	= &f2fs_attr_ops,
 	.release	= f2fs_sb_release,
 };
 
+static struct kobj_type f2fs_ktype = {
+	.sysfs_ops	= &f2fs_attr_ops,
+};
+
+static struct kset f2fs_kset = {
+	.kobj   = {.ktype = &f2fs_ktype},
+};
+
+static struct kobj_type f2fs_feat_ktype = {
+	.default_attrs	= f2fs_feat_attrs,
+	.sysfs_ops	= &f2fs_attr_ops,
+};
+
+static struct kobject f2fs_feat = {
+	.kset	= &f2fs_kset,
+};
+
 static int segment_info_seq_show(struct seq_file *seq, void *offset)
 {
 	struct super_block *sb = seq->private;
@@ -306,18 +409,29 @@ F2FS_PROC_FILE_DEF(segment_bits);
 
 int __init f2fs_init_sysfs(void)
 {
-	f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
+	int ret;
 
-	f2fs_kset = kset_create_and_add("f2fs", NULL, fs_kobj);
-	if (!f2fs_kset)
-		return -ENOMEM;
-	return 0;
+	kobject_set_name(&f2fs_kset.kobj, "f2fs");
+	f2fs_kset.kobj.parent = fs_kobj;
+	ret = kset_register(&f2fs_kset);
+	if (ret)
+		return ret;
+
+	ret = kobject_init_and_add(&f2fs_feat, &f2fs_feat_ktype,
+				   NULL, "features");
+	if (ret)
+		kset_unregister(&f2fs_kset);
+	else
+		f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
+	return ret;
 }
 
 void f2fs_exit_sysfs(void)
 {
-	kset_unregister(f2fs_kset);
+	kobject_put(&f2fs_feat);
+	kset_unregister(&f2fs_kset);
 	remove_proc_entry("fs/f2fs", NULL);
+	f2fs_proc_root = NULL;
 }
 
 int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
@@ -325,6 +439,13 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 	struct super_block *sb = sbi->sb;
 	int err;
 
+	sbi->s_kobj.kset = &f2fs_kset;
+	init_completion(&sbi->s_kobj_unregister);
+	err = kobject_init_and_add(&sbi->s_kobj, &f2fs_sb_ktype, NULL,
+				"%s", sb->s_id);
+	if (err)
+		return err;
+
 	if (f2fs_proc_root)
 		sbi->s_proc = proc_mkdir(sb->s_id, f2fs_proc_root);
 
@@ -334,32 +455,15 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 		proc_create_data("segment_bits", S_IRUGO, sbi->s_proc,
 				 &f2fs_seq_segment_bits_fops, sb);
 	}
-
-	sbi->s_kobj.kset = f2fs_kset;
-	init_completion(&sbi->s_kobj_unregister);
-	err = kobject_init_and_add(&sbi->s_kobj, &f2fs_ktype, NULL,
-							"%s", sb->s_id);
-	if (err)
-		goto err_out;
 	return 0;
-err_out:
-	if (sbi->s_proc) {
-		remove_proc_entry("segment_info", sbi->s_proc);
-		remove_proc_entry("segment_bits", sbi->s_proc);
-		remove_proc_entry(sb->s_id, f2fs_proc_root);
-	}
-	return err;
 }
 
 void f2fs_unregister_sysfs(struct f2fs_sb_info *sbi)
 {
-	kobject_del(&sbi->s_kobj);
-	kobject_put(&sbi->s_kobj);
-	wait_for_completion(&sbi->s_kobj_unregister);
-
 	if (sbi->s_proc) {
 		remove_proc_entry("segment_info", sbi->s_proc);
 		remove_proc_entry("segment_bits", sbi->s_proc);
 		remove_proc_entry(sbi->sb->s_id, f2fs_proc_root);
 	}
+	kobject_del(&sbi->s_kobj);
 }