/*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */

  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>

  #include <linux/kobject.h>

  #include <linux/bug.h>

  #include <linux/genhd.h>

  #include <linux/debugfs.h>

  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"

  #include "sysfs.h"

  #include "volumes.h"

  static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj);

  static inline struct btrfs_fs_devices *to_fs_devs(struct kobject *kobj);

  static u64 get_features(struct btrfs_fs_info *fs_info,
  			enum btrfs_feature_set set)

  {

  	struct btrfs_super_block *disk_super = fs_info->super_copy;
  	if (set == FEAT_COMPAT)
  		return btrfs_super_compat_flags(disk_super);
  	else if (set == FEAT_COMPAT_RO)
  		return btrfs_super_compat_ro_flags(disk_super);
  	else
  		return btrfs_super_incompat_flags(disk_super);

  }

  static void set_features(struct btrfs_fs_info *fs_info,
  			 enum btrfs_feature_set set, u64 features)
  {
  	struct btrfs_super_block *disk_super = fs_info->super_copy;
  	if (set == FEAT_COMPAT)
  		btrfs_set_super_compat_flags(disk_super, features);
  	else if (set == FEAT_COMPAT_RO)
  		btrfs_set_super_compat_ro_flags(disk_super, features);
  	else
  		btrfs_set_super_incompat_flags(disk_super, features);
  }
  
  static int can_modify_feature(struct btrfs_feature_attr *fa)
  {
  	int val = 0;
  	u64 set, clear;
  	switch (fa->feature_set) {
  	case FEAT_COMPAT:
  		set = BTRFS_FEATURE_COMPAT_SAFE_SET;
  		clear = BTRFS_FEATURE_COMPAT_SAFE_CLEAR;
  		break;
  	case FEAT_COMPAT_RO:
  		set = BTRFS_FEATURE_COMPAT_RO_SAFE_SET;
  		clear = BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR;
  		break;
  	case FEAT_INCOMPAT:
  		set = BTRFS_FEATURE_INCOMPAT_SAFE_SET;
  		clear = BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR;
  		break;
  	default:

  		pr_warn("btrfs: sysfs: unknown feature set %d
  ",

  				fa->feature_set);
  		return 0;

  	}
  
  	if (set & fa->feature_bit)
  		val |= 1;
  	if (clear & fa->feature_bit)
  		val |= 2;
  
  	return val;
  }

  static ssize_t btrfs_feature_attr_show(struct kobject *kobj,
  				       struct kobj_attribute *a, char *buf)

  {

  	int val = 0;

  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	struct btrfs_feature_attr *fa = to_btrfs_feature_attr(a);

  	if (fs_info) {

  		u64 features = get_features(fs_info, fa->feature_set);
  		if (features & fa->feature_bit)
  			val = 1;

  	} else
  		val = can_modify_feature(fa);

  
  	return snprintf(buf, PAGE_SIZE, "%d
  ", val);

  }

  static ssize_t btrfs_feature_attr_store(struct kobject *kobj,
  					struct kobj_attribute *a,
  					const char *buf, size_t count)
  {
  	struct btrfs_fs_info *fs_info;
  	struct btrfs_feature_attr *fa = to_btrfs_feature_attr(a);

  	u64 features, set, clear;
  	unsigned long val;
  	int ret;
  
  	fs_info = to_fs_info(kobj);
  	if (!fs_info)
  		return -EPERM;

  	if (sb_rdonly(fs_info->sb))

  		return -EROFS;

  	ret = kstrtoul(skip_spaces(buf), 0, &val);
  	if (ret)
  		return ret;
  
  	if (fa->feature_set == FEAT_COMPAT) {
  		set = BTRFS_FEATURE_COMPAT_SAFE_SET;
  		clear = BTRFS_FEATURE_COMPAT_SAFE_CLEAR;
  	} else if (fa->feature_set == FEAT_COMPAT_RO) {
  		set = BTRFS_FEATURE_COMPAT_RO_SAFE_SET;
  		clear = BTRFS_FEATURE_COMPAT_RO_SAFE_CLEAR;
  	} else {
  		set = BTRFS_FEATURE_INCOMPAT_SAFE_SET;
  		clear = BTRFS_FEATURE_INCOMPAT_SAFE_CLEAR;
  	}
  
  	features = get_features(fs_info, fa->feature_set);
  
  	/* Nothing to do */
  	if ((val && (features & fa->feature_bit)) ||
  	    (!val && !(features & fa->feature_bit)))
  		return count;
  
  	if ((val && !(set & fa->feature_bit)) ||
  	    (!val && !(clear & fa->feature_bit))) {
  		btrfs_info(fs_info,
  			"%sabling feature %s on mounted fs is not supported.",
  			val ? "En" : "Dis", fa->kobj_attr.attr.name);
  		return -EPERM;
  	}
  
  	btrfs_info(fs_info, "%s %s feature flag",
  		   val ? "Setting" : "Clearing", fa->kobj_attr.attr.name);

  	spin_lock(&fs_info->super_lock);
  	features = get_features(fs_info, fa->feature_set);
  	if (val)
  		features |= fa->feature_bit;
  	else
  		features &= ~fa->feature_bit;
  	set_features(fs_info, fa->feature_set, features);
  	spin_unlock(&fs_info->super_lock);

  	/*
  	 * We don't want to do full transaction commit from inside sysfs
  	 */
  	btrfs_set_pending(fs_info, COMMIT);
  	wake_up_process(fs_info->transaction_kthread);

  
  	return count;
  }

  static umode_t btrfs_feature_visible(struct kobject *kobj,
  				     struct attribute *attr, int unused)

  {

  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
  	umode_t mode = attr->mode;
  
  	if (fs_info) {
  		struct btrfs_feature_attr *fa;
  		u64 features;
  
  		fa = attr_to_btrfs_feature_attr(attr);
  		features = get_features(fs_info, fa->feature_set);

  		if (can_modify_feature(fa))
  			mode |= S_IWUSR;
  		else if (!(features & fa->feature_bit))

  			mode = 0;
  	}
  
  	return mode;

  }
  
  BTRFS_FEAT_ATTR_INCOMPAT(mixed_backref, MIXED_BACKREF);
  BTRFS_FEAT_ATTR_INCOMPAT(default_subvol, DEFAULT_SUBVOL);
  BTRFS_FEAT_ATTR_INCOMPAT(mixed_groups, MIXED_GROUPS);
  BTRFS_FEAT_ATTR_INCOMPAT(compress_lzo, COMPRESS_LZO);

  BTRFS_FEAT_ATTR_INCOMPAT(compress_zstd, COMPRESS_ZSTD);

  BTRFS_FEAT_ATTR_INCOMPAT(big_metadata, BIG_METADATA);
  BTRFS_FEAT_ATTR_INCOMPAT(extended_iref, EXTENDED_IREF);
  BTRFS_FEAT_ATTR_INCOMPAT(raid56, RAID56);
  BTRFS_FEAT_ATTR_INCOMPAT(skinny_metadata, SKINNY_METADATA);

  BTRFS_FEAT_ATTR_INCOMPAT(no_holes, NO_HOLES);

  BTRFS_FEAT_ATTR_COMPAT_RO(free_space_tree, FREE_SPACE_TREE);

  
  static struct attribute *btrfs_supported_feature_attrs[] = {
  	BTRFS_FEAT_ATTR_PTR(mixed_backref),
  	BTRFS_FEAT_ATTR_PTR(default_subvol),
  	BTRFS_FEAT_ATTR_PTR(mixed_groups),
  	BTRFS_FEAT_ATTR_PTR(compress_lzo),

  	BTRFS_FEAT_ATTR_PTR(compress_zstd),

  	BTRFS_FEAT_ATTR_PTR(big_metadata),
  	BTRFS_FEAT_ATTR_PTR(extended_iref),
  	BTRFS_FEAT_ATTR_PTR(raid56),
  	BTRFS_FEAT_ATTR_PTR(skinny_metadata),

  	BTRFS_FEAT_ATTR_PTR(no_holes),

  	BTRFS_FEAT_ATTR_PTR(free_space_tree),

  	NULL
  };
  
  static const struct attribute_group btrfs_feature_attr_group = {
  	.name = "features",

  	.is_visible = btrfs_feature_visible,

  	.attrs = btrfs_supported_feature_attrs,
  };

  static ssize_t btrfs_show_u64(u64 *value_ptr, spinlock_t *lock, char *buf)
  {
  	u64 val;
  	if (lock)
  		spin_lock(lock);
  	val = *value_ptr;
  	if (lock)
  		spin_unlock(lock);
  	return snprintf(buf, PAGE_SIZE, "%llu
  ", val);
  }
  
  static ssize_t global_rsv_size_show(struct kobject *kobj,
  				    struct kobj_attribute *ka, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj->parent);
  	struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
  	return btrfs_show_u64(&block_rsv->size, &block_rsv->lock, buf);
  }

  BTRFS_ATTR(global_rsv_size, global_rsv_size_show);

  
  static ssize_t global_rsv_reserved_show(struct kobject *kobj,
  					struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj->parent);
  	struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
  	return btrfs_show_u64(&block_rsv->reserved, &block_rsv->lock, buf);
  }

  BTRFS_ATTR(global_rsv_reserved, global_rsv_reserved_show);

  
  #define to_space_info(_kobj) container_of(_kobj, struct btrfs_space_info, kobj)

  #define to_raid_kobj(_kobj) container_of(_kobj, struct raid_kobject, kobj)

  
  static ssize_t raid_bytes_show(struct kobject *kobj,
  			       struct kobj_attribute *attr, char *buf);
  BTRFS_RAID_ATTR(total_bytes, raid_bytes_show);
  BTRFS_RAID_ATTR(used_bytes, raid_bytes_show);
  
  static ssize_t raid_bytes_show(struct kobject *kobj,
  			       struct kobj_attribute *attr, char *buf)
  
  {
  	struct btrfs_space_info *sinfo = to_space_info(kobj->parent);
  	struct btrfs_block_group_cache *block_group;

  	int index = to_raid_kobj(kobj)->raid_type;

  	u64 val = 0;
  
  	down_read(&sinfo->groups_sem);
  	list_for_each_entry(block_group, &sinfo->block_groups[index], list) {
  		if (&attr->attr == BTRFS_RAID_ATTR_PTR(total_bytes))
  			val += block_group->key.offset;
  		else
  			val += btrfs_block_group_used(&block_group->item);
  	}
  	up_read(&sinfo->groups_sem);
  	return snprintf(buf, PAGE_SIZE, "%llu
  ", val);
  }
  
  static struct attribute *raid_attributes[] = {
  	BTRFS_RAID_ATTR_PTR(total_bytes),
  	BTRFS_RAID_ATTR_PTR(used_bytes),
  	NULL
  };
  
  static void release_raid_kobj(struct kobject *kobj)
  {

  	kfree(to_raid_kobj(kobj));

  }
  
  struct kobj_type btrfs_raid_ktype = {
  	.sysfs_ops = &kobj_sysfs_ops,
  	.release = release_raid_kobj,
  	.default_attrs = raid_attributes,
  };
  
  #define SPACE_INFO_ATTR(field)						\
  static ssize_t btrfs_space_info_show_##field(struct kobject *kobj,	\
  					     struct kobj_attribute *a,	\
  					     char *buf)			\
  {									\
  	struct btrfs_space_info *sinfo = to_space_info(kobj);		\
  	return btrfs_show_u64(&sinfo->field, &sinfo->lock, buf);	\
  }									\

  BTRFS_ATTR(field, btrfs_space_info_show_##field)

  
  static ssize_t btrfs_space_info_show_total_bytes_pinned(struct kobject *kobj,
  						       struct kobj_attribute *a,
  						       char *buf)
  {
  	struct btrfs_space_info *sinfo = to_space_info(kobj);
  	s64 val = percpu_counter_sum(&sinfo->total_bytes_pinned);
  	return snprintf(buf, PAGE_SIZE, "%lld
  ", val);
  }
  
  SPACE_INFO_ATTR(flags);
  SPACE_INFO_ATTR(total_bytes);
  SPACE_INFO_ATTR(bytes_used);
  SPACE_INFO_ATTR(bytes_pinned);
  SPACE_INFO_ATTR(bytes_reserved);
  SPACE_INFO_ATTR(bytes_may_use);

  SPACE_INFO_ATTR(bytes_readonly);

  SPACE_INFO_ATTR(disk_used);
  SPACE_INFO_ATTR(disk_total);

  BTRFS_ATTR(total_bytes_pinned, btrfs_space_info_show_total_bytes_pinned);

  
  static struct attribute *space_info_attrs[] = {
  	BTRFS_ATTR_PTR(flags),
  	BTRFS_ATTR_PTR(total_bytes),
  	BTRFS_ATTR_PTR(bytes_used),
  	BTRFS_ATTR_PTR(bytes_pinned),
  	BTRFS_ATTR_PTR(bytes_reserved),
  	BTRFS_ATTR_PTR(bytes_may_use),

  	BTRFS_ATTR_PTR(bytes_readonly),

  	BTRFS_ATTR_PTR(disk_used),
  	BTRFS_ATTR_PTR(disk_total),
  	BTRFS_ATTR_PTR(total_bytes_pinned),
  	NULL,
  };
  
  static void space_info_release(struct kobject *kobj)
  {
  	struct btrfs_space_info *sinfo = to_space_info(kobj);
  	percpu_counter_destroy(&sinfo->total_bytes_pinned);
  	kfree(sinfo);
  }
  
  struct kobj_type space_info_ktype = {
  	.sysfs_ops = &kobj_sysfs_ops,
  	.release = space_info_release,
  	.default_attrs = space_info_attrs,
  };
  
  static const struct attribute *allocation_attrs[] = {
  	BTRFS_ATTR_PTR(global_rsv_reserved),
  	BTRFS_ATTR_PTR(global_rsv_size),
  	NULL,
  };

  static ssize_t btrfs_label_show(struct kobject *kobj,
  				struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	char *label = fs_info->super_copy->label;

  	ssize_t ret;
  
  	spin_lock(&fs_info->super_lock);
  	ret = snprintf(buf, PAGE_SIZE, label[0] ? "%s
  " : "%s", label);
  	spin_unlock(&fs_info->super_lock);
  
  	return ret;

  }
  
  static ssize_t btrfs_label_store(struct kobject *kobj,
  				 struct kobj_attribute *a,
  				 const char *buf, size_t len)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	size_t p_len;

  	if (!fs_info)
  		return -EPERM;

  	if (sb_rdonly(fs_info->sb))

  		return -EROFS;

  	/*
  	 * p_len is the len until the first occurrence of either
  	 * '
  ' or '\0'
  	 */
  	p_len = strcspn(buf, "
  ");
  
  	if (p_len >= BTRFS_LABEL_SIZE)

  		return -EINVAL;

  	spin_lock(&fs_info->super_lock);

  	memset(fs_info->super_copy->label, 0, BTRFS_LABEL_SIZE);
  	memcpy(fs_info->super_copy->label, buf, p_len);

  	spin_unlock(&fs_info->super_lock);

  	/*
  	 * We don't want to do full transaction commit from inside sysfs
  	 */
  	btrfs_set_pending(fs_info, COMMIT);
  	wake_up_process(fs_info->transaction_kthread);

  	return len;

  }

  BTRFS_ATTR_RW(label, btrfs_label_show, btrfs_label_store);

  static ssize_t btrfs_nodesize_show(struct kobject *kobj,
  				struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	return snprintf(buf, PAGE_SIZE, "%u
  ", fs_info->super_copy->nodesize);

  }

  BTRFS_ATTR(nodesize, btrfs_nodesize_show);

  
  static ssize_t btrfs_sectorsize_show(struct kobject *kobj,
  				struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			fs_info->super_copy->sectorsize);

  }

  BTRFS_ATTR(sectorsize, btrfs_sectorsize_show);

  
  static ssize_t btrfs_clone_alignment_show(struct kobject *kobj,
  				struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);

  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			fs_info->super_copy->sectorsize);

  }

  BTRFS_ATTR(clone_alignment, btrfs_clone_alignment_show);

  static ssize_t quota_override_show(struct kobject *kobj,
  				   struct kobj_attribute *a, char *buf)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
  	int quota_override;
  
  	quota_override = test_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags);
  	return snprintf(buf, PAGE_SIZE, "%d
  ", quota_override);
  }
  
  static ssize_t quota_override_store(struct kobject *kobj,
  				    struct kobj_attribute *a,
  				    const char *buf, size_t len)
  {
  	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
  	unsigned long knob;
  	int err;
  
  	if (!fs_info)
  		return -EPERM;
  
  	if (!capable(CAP_SYS_RESOURCE))
  		return -EPERM;
  
  	err = kstrtoul(buf, 10, &knob);
  	if (err)
  		return err;
  	if (knob > 1)
  		return -EINVAL;
  
  	if (knob)
  		set_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags);
  	else
  		clear_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags);
  
  	return len;
  }
  
  BTRFS_ATTR_RW(quota_override, quota_override_show, quota_override_store);

  static const struct attribute *btrfs_attrs[] = {

  	BTRFS_ATTR_PTR(label),

  	BTRFS_ATTR_PTR(nodesize),
  	BTRFS_ATTR_PTR(sectorsize),
  	BTRFS_ATTR_PTR(clone_alignment),

  	BTRFS_ATTR_PTR(quota_override),

  	NULL,
  };

  static void btrfs_release_fsid_kobj(struct kobject *kobj)

  {

  	struct btrfs_fs_devices *fs_devs = to_fs_devs(kobj);

  	memset(&fs_devs->fsid_kobj, 0, sizeof(struct kobject));

  	complete(&fs_devs->kobj_unregister);

  }
  
  static struct kobj_type btrfs_ktype = {
  	.sysfs_ops	= &kobj_sysfs_ops,

  	.release	= btrfs_release_fsid_kobj,

  };

  static inline struct btrfs_fs_devices *to_fs_devs(struct kobject *kobj)
  {
  	if (kobj->ktype != &btrfs_ktype)
  		return NULL;

  	return container_of(kobj, struct btrfs_fs_devices, fsid_kobj);

  }

  static inline struct btrfs_fs_info *to_fs_info(struct kobject *kobj)
  {
  	if (kobj->ktype != &btrfs_ktype)
  		return NULL;

  	return to_fs_devs(kobj)->fs_info;

  }

  #define NUM_FEATURE_BITS 64
  static char btrfs_unknown_feature_names[3][NUM_FEATURE_BITS][13];
  static struct btrfs_feature_attr btrfs_feature_attrs[3][NUM_FEATURE_BITS];

  static const u64 supported_feature_masks[3] = {

  	[FEAT_COMPAT]    = BTRFS_FEATURE_COMPAT_SUPP,
  	[FEAT_COMPAT_RO] = BTRFS_FEATURE_COMPAT_RO_SUPP,
  	[FEAT_INCOMPAT]  = BTRFS_FEATURE_INCOMPAT_SUPP,
  };
  
  static int addrm_unknown_feature_attrs(struct btrfs_fs_info *fs_info, bool add)
  {
  	int set;
  
  	for (set = 0; set < FEAT_MAX; set++) {
  		int i;
  		struct attribute *attrs[2];
  		struct attribute_group agroup = {
  			.name = "features",
  			.attrs = attrs,
  		};
  		u64 features = get_features(fs_info, set);
  		features &= ~supported_feature_masks[set];
  
  		if (!features)
  			continue;
  
  		attrs[1] = NULL;
  		for (i = 0; i < NUM_FEATURE_BITS; i++) {
  			struct btrfs_feature_attr *fa;
  
  			if (!(features & (1ULL << i)))
  				continue;
  
  			fa = &btrfs_feature_attrs[set][i];
  			attrs[0] = &fa->kobj_attr.attr;
  			if (add) {
  				int ret;

  				ret = sysfs_merge_group(&fs_info->fs_devices->fsid_kobj,

  							&agroup);
  				if (ret)
  					return ret;
  			} else

  				sysfs_unmerge_group(&fs_info->fs_devices->fsid_kobj,

  						    &agroup);
  		}
  
  	}
  	return 0;
  }

  static void __btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs)

  {

  	if (fs_devs->device_dir_kobj) {
  		kobject_del(fs_devs->device_dir_kobj);
  		kobject_put(fs_devs->device_dir_kobj);
  		fs_devs->device_dir_kobj = NULL;

  	}

  	if (fs_devs->fsid_kobj.state_initialized) {
  		kobject_del(&fs_devs->fsid_kobj);
  		kobject_put(&fs_devs->fsid_kobj);

  		wait_for_completion(&fs_devs->kobj_unregister);
  	}

  }

  /* when fs_devs is NULL it will remove all fsid kobject */

  void btrfs_sysfs_remove_fsid(struct btrfs_fs_devices *fs_devs)

  {
  	struct list_head *fs_uuids = btrfs_get_fs_uuids();
  
  	if (fs_devs) {
  		__btrfs_sysfs_remove_fsid(fs_devs);
  		return;
  	}
  
  	list_for_each_entry(fs_devs, fs_uuids, list) {
  		__btrfs_sysfs_remove_fsid(fs_devs);
  	}
  }

  void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)

  {

  	btrfs_reset_fs_info_ptr(fs_info);

  	if (fs_info->space_info_kobj) {
  		sysfs_remove_files(fs_info->space_info_kobj, allocation_attrs);
  		kobject_del(fs_info->space_info_kobj);
  		kobject_put(fs_info->space_info_kobj);
  	}

  	addrm_unknown_feature_attrs(fs_info, false);

  	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj, &btrfs_feature_attr_group);
  	sysfs_remove_files(&fs_info->fs_devices->fsid_kobj, btrfs_attrs);

  	btrfs_sysfs_rm_device_link(fs_info->fs_devices, NULL);

  }

  const char * const btrfs_feature_set_names[3] = {
  	[FEAT_COMPAT]	 = "compat",
  	[FEAT_COMPAT_RO] = "compat_ro",
  	[FEAT_INCOMPAT]	 = "incompat",
  };

  char *btrfs_printable_features(enum btrfs_feature_set set, u64 flags)
  {
  	size_t bufsize = 4096; /* safe max, 64 names * 64 bytes */
  	int len = 0;
  	int i;
  	char *str;
  
  	str = kmalloc(bufsize, GFP_KERNEL);
  	if (!str)
  		return str;
  
  	for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[set]); i++) {
  		const char *name;
  
  		if (!(flags & (1ULL << i)))
  			continue;
  
  		name = btrfs_feature_attrs[set][i].kobj_attr.attr.name;
  		len += snprintf(str + len, bufsize - len, "%s%s",
  				len ? "," : "", name);
  	}
  
  	return str;
  }

  static void init_feature_attrs(void)
  {
  	struct btrfs_feature_attr *fa;
  	int set, i;
  
  	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names) !=
  		     ARRAY_SIZE(btrfs_feature_attrs));
  	BUILD_BUG_ON(ARRAY_SIZE(btrfs_unknown_feature_names[0]) !=
  		     ARRAY_SIZE(btrfs_feature_attrs[0]));

  	memset(btrfs_feature_attrs, 0, sizeof(btrfs_feature_attrs));
  	memset(btrfs_unknown_feature_names, 0,
  	       sizeof(btrfs_unknown_feature_names));

  	for (i = 0; btrfs_supported_feature_attrs[i]; i++) {
  		struct btrfs_feature_attr *sfa;
  		struct attribute *a = btrfs_supported_feature_attrs[i];

  		int bit;

  		sfa = attr_to_btrfs_feature_attr(a);

  		bit = ilog2(sfa->feature_bit);
  		fa = &btrfs_feature_attrs[sfa->feature_set][bit];

  
  		fa->kobj_attr.attr.name = sfa->kobj_attr.attr.name;
  	}
  
  	for (set = 0; set < FEAT_MAX; set++) {
  		for (i = 0; i < ARRAY_SIZE(btrfs_feature_attrs[set]); i++) {
  			char *name = btrfs_unknown_feature_names[set][i];
  			fa = &btrfs_feature_attrs[set][i];
  
  			if (fa->kobj_attr.attr.name)
  				continue;
  
  			snprintf(name, 13, "%s:%u",
  				 btrfs_feature_set_names[set], i);
  
  			fa->kobj_attr.attr.name = name;
  			fa->kobj_attr.attr.mode = S_IRUGO;
  			fa->feature_set = set;
  			fa->feature_bit = 1ULL << i;
  		}
  	}
  }

  /* when one_device is NULL, it removes all device links */

  int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices,

  		struct btrfs_device *one_device)
  {
  	struct hd_struct *disk;
  	struct kobject *disk_kobj;

  	if (!fs_devices->device_dir_kobj)

  		return -EINVAL;

  	if (one_device && one_device->bdev) {

  		disk = one_device->bdev->bd_part;
  		disk_kobj = &part_to_dev(disk)->kobj;

  		sysfs_remove_link(fs_devices->device_dir_kobj,

  						disk_kobj->name);
  	}

  	if (one_device)
  		return 0;
  
  	list_for_each_entry(one_device,

  			&fs_devices->devices, dev_list) {

  		if (!one_device->bdev)
  			continue;
  		disk = one_device->bdev->bd_part;
  		disk_kobj = &part_to_dev(disk)->kobj;

  		sysfs_remove_link(fs_devices->device_dir_kobj,

  						disk_kobj->name);
  	}

  	return 0;
  }

  int btrfs_sysfs_add_device(struct btrfs_fs_devices *fs_devs)

  {

  	if (!fs_devs->device_dir_kobj)
  		fs_devs->device_dir_kobj = kobject_create_and_add("devices",

  						&fs_devs->fsid_kobj);

  	if (!fs_devs->device_dir_kobj)

  		return -ENOMEM;

  	return 0;
  }

  int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices,

  				struct btrfs_device *one_device)

  {
  	int error = 0;

  	struct btrfs_device *dev;

  	list_for_each_entry(dev, &fs_devices->devices, dev_list) {

  		struct hd_struct *disk;
  		struct kobject *disk_kobj;
  
  		if (!dev->bdev)
  			continue;

  		if (one_device && one_device != dev)
  			continue;

  		disk = dev->bdev->bd_part;
  		disk_kobj = &part_to_dev(disk)->kobj;

  		error = sysfs_create_link(fs_devices->device_dir_kobj,

  					  disk_kobj, disk_kobj->name);
  		if (error)
  			break;
  	}
  
  	return error;
  }

  /* /sys/fs/btrfs/ entry */
  static struct kset *btrfs_kset;

  /* /sys/kernel/debug/btrfs */
  static struct dentry *btrfs_debugfs_root_dentry;
  
  /* Debugging tunables and exported data */
  u64 btrfs_debugfs_test;

  /*
   * Can be called by the device discovery thread.
   * And parent can be specified for seed device
   */

  int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,

  				struct kobject *parent)

  {
  	int error;

  	init_completion(&fs_devs->kobj_unregister);

  	fs_devs->fsid_kobj.kset = btrfs_kset;
  	error = kobject_init_and_add(&fs_devs->fsid_kobj,

  				&btrfs_ktype, parent, "%pU", fs_devs->fsid);

  	return error;
  }

  int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)

  {
  	int error;

  	struct btrfs_fs_devices *fs_devs = fs_info->fs_devices;

  	struct kobject *fsid_kobj = &fs_devs->fsid_kobj;

  	btrfs_set_fs_info_ptr(fs_info);

  	error = btrfs_sysfs_add_device_link(fs_devs, NULL);

  	if (error)

  		return error;

  	error = sysfs_create_files(fsid_kobj, btrfs_attrs);

  	if (error) {

  		btrfs_sysfs_rm_device_link(fs_devs, NULL);

  		return error;
  	}

  	error = sysfs_create_group(fsid_kobj,

  				   &btrfs_feature_attr_group);
  	if (error)
  		goto failure;

  	error = addrm_unknown_feature_attrs(fs_info, true);

  	if (error)
  		goto failure;

  	fs_info->space_info_kobj = kobject_create_and_add("allocation",

  						  fsid_kobj);

  	if (!fs_info->space_info_kobj) {
  		error = -ENOMEM;
  		goto failure;
  	}
  
  	error = sysfs_create_files(fs_info->space_info_kobj, allocation_attrs);
  	if (error)
  		goto failure;

  	return 0;
  failure:

  	btrfs_sysfs_remove_mounted(fs_info);

  	return error;
  }

  
  /*
   * Change per-fs features in /sys/fs/btrfs/UUID/features to match current
   * values in superblock. Call after any changes to incompat/compat_ro flags
   */
  void btrfs_sysfs_feature_update(struct btrfs_fs_info *fs_info,
  		u64 bit, enum btrfs_feature_set set)
  {
  	struct btrfs_fs_devices *fs_devs;
  	struct kobject *fsid_kobj;
  	u64 features;
  	int ret;
  
  	if (!fs_info)
  		return;
  
  	features = get_features(fs_info, set);
  	ASSERT(bit & supported_feature_masks[set]);
  
  	fs_devs = fs_info->fs_devices;
  	fsid_kobj = &fs_devs->fsid_kobj;

  	if (!fsid_kobj->state_initialized)
  		return;

  	/*
  	 * FIXME: this is too heavy to update just one value, ideally we'd like
  	 * to use sysfs_update_group but some refactoring is needed first.
  	 */
  	sysfs_remove_group(fsid_kobj, &btrfs_feature_attr_group);
  	ret = sysfs_create_group(fsid_kobj, &btrfs_feature_attr_group);
  }

  static int btrfs_init_debugfs(void)
  {
  #ifdef CONFIG_DEBUG_FS
  	btrfs_debugfs_root_dentry = debugfs_create_dir("btrfs", NULL);
  	if (!btrfs_debugfs_root_dentry)
  		return -ENOMEM;

  	/*
  	 * Example code, how to export data through debugfs.
  	 *
  	 * file:        /sys/kernel/debug/btrfs/test
  	 * contents of: btrfs_debugfs_test
  	 */
  #ifdef CONFIG_BTRFS_DEBUG

  	debugfs_create_u64("test", S_IRUGO | S_IWUSR, btrfs_debugfs_root_dentry,

  			&btrfs_debugfs_test);
  #endif

  
  #endif

  	return 0;
  }

  int btrfs_init_sysfs(void)

  {

  	int ret;

  	btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);
  	if (!btrfs_kset)
  		return -ENOMEM;

  	ret = btrfs_init_debugfs();
  	if (ret)

  		goto out1;

  	init_feature_attrs();

  	ret = sysfs_create_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);

  	if (ret)
  		goto out2;
  
  	return 0;
  out2:
  	debugfs_remove_recursive(btrfs_debugfs_root_dentry);
  out1:
  	kset_unregister(btrfs_kset);

  	return ret;

  }

  void btrfs_exit_sysfs(void)

  {

  	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);

  	kset_unregister(btrfs_kset);

  	debugfs_remove_recursive(btrfs_debugfs_root_dentry);

  }