Commit f3623740 authored by Anand Jain's avatar Anand Jain Committed by David Sterba
Browse files

btrfs: sysfs: show temp_fsid feature 



This adds sysfs objects to indicate temp_fsid feature support and
its status.

  /sys/fs/btrfs/features/temp_fsid
  /sys/fs/btrfs/<UUID>/temp_fsid

For example:

   Consider two cloned and mounted devices.

      $ blkid /dev/sdc[1-2]
      /dev/sdc1: UUID="509ad44b-ad2a-4a8a-bc8d-fe69db7220d5" ..
      /dev/sdc2: UUID="509ad44b-ad2a-4a8a-bc8d-fe69db7220d5" ..

   One gets actual fsid, and the other gets the temp_fsid when
   mounted.

      $ btrfs filesystem show -m
      Label: none  uuid: 509ad44b-ad2a-4a8a-bc8d-fe69db7220d5
	      Total devices 1 FS bytes used 54.14MiB
	      devid    1 size 300.00MiB used 144.00MiB path /dev/sdc1

      Label: none  uuid: 33bad74e-c91b-43a5-aef8-b3cab97ae63a
	      Total devices 1 FS bytes used 54.14MiB
	      devid    1 size 300.00MiB used 144.00MiB path /dev/sdc2

   Their sysfs as below.

      $ cat /sys/fs/btrfs/features/temp_fsid
      0

      $ cat /sys/fs/btrfs/509ad44b-ad2a-4a8a-bc8d-fe69db7220d5/temp_fsid
      0

      $ cat /sys/fs/btrfs/33bad74e-c91b-43a5-aef8-b3cab97ae63a/temp_fsid
      1

Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ac6ea6a9

fs/btrfs/sysfs.c

+18 −0
Original line number Diff line number Diff line
@@ -425,6 +425,13 @@ static ssize_t acl_show(struct kobject *kobj, struct kobj_attribute *a, char *bu 
}

BTRFS_ATTR(static_feature, acl, acl_show);



static ssize_t temp_fsid_supported_show(struct kobject *kobj,

					struct kobj_attribute *a, char *buf)

{

	return sysfs_emit(buf, "0\n");

}

BTRFS_ATTR(static_feature, temp_fsid, temp_fsid_supported_show);



/*

 * Features which only depend on kernel version.

 *
@@ -438,6 +445,7 @@ static struct attribute *btrfs_supported_static_feature_attrs[] = { 
	BTRFS_ATTR_PTR(static_feature, send_stream_version),

	BTRFS_ATTR_PTR(static_feature, supported_rescue_options),

	BTRFS_ATTR_PTR(static_feature, supported_sectorsizes),

	BTRFS_ATTR_PTR(static_feature, temp_fsid),

	NULL

};
@@ -1205,6 +1213,15 @@ static ssize_t btrfs_generation_show(struct kobject *kobj, 
}

BTRFS_ATTR(, generation, btrfs_generation_show);



static ssize_t btrfs_temp_fsid_show(struct kobject *kobj,

				    struct kobj_attribute *a, char *buf)

{

	struct btrfs_fs_info *fs_info = to_fs_info(kobj);



	return sysfs_emit(buf, "%d\n", fs_info->fs_devices->temp_fsid);

}

BTRFS_ATTR(, temp_fsid, btrfs_temp_fsid_show);



static const char * const btrfs_read_policy_name[] = { "pid" };



static ssize_t btrfs_read_policy_show(struct kobject *kobj,
@@ -1307,6 +1324,7 @@ static const struct attribute *btrfs_attrs[] = { 
	BTRFS_ATTR_PTR(, read_policy),

	BTRFS_ATTR_PTR(, bg_reclaim_threshold),

	BTRFS_ATTR_PTR(, commit_stats),

	BTRFS_ATTR_PTR(, temp_fsid),

	NULL,

};