Commit 668e48af authored by Anand Jain's avatar Anand Jain Committed by David Sterba
Browse files

btrfs: sysfs, add devid/dev_state kobject and device attributes 



New sysfs attributes that track the filesystem status of devices, stored
in the per-filesystem directory in /sys/fs/btrfs/FSID/devinfo . There's
a directory for each device, with name corresponding to the numerical
device id.

  in_fs_metadata    - device is in the list of fs metadata
  missing           - device is missing (no device node or block device)
  replace_target    - device is target of replace
  writeable         - writes from fs are allowed

These attributes reflect the state of the device::dev_state and created
at mount time.

Sample output:
  $ pwd
   /sys/fs/btrfs/6e1961f1-5918-4ecc-a22f-948897b409f7/devinfo/1/
  $ ls
    in_fs_metadata  missing  replace_target  writeable
  $ cat missing
    0

The output from these attributes are 0 or 1. 0 indicates unset and 1
indicates set.  These attributes are readonly.

It is observed that the device delete thread and sysfs read thread will
not race because the delete thread calls sysfs kobject_put() which in
turn waits for existing sysfs read to complete.

Note for device replace devid swap:

During the replace the target device temporarily assumes devid 0 before
assigning the devid of the soruce device.

In btrfs_dev_replace_finishing() we remove source sysfs devid using the
function btrfs_sysfs_remove_devices_attr(), so after that call
kobject_rename() to update the devid in the sysfs.  This adds and calls
btrfs_sysfs_update_devid() helper function to update the device id.

Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 1776ad17

fs/btrfs/dev-replace.c

+1 −0
Original line number Diff line number Diff line
@@ -707,6 +707,7 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, 


	/* replace the sysfs entry */

	btrfs_sysfs_rm_device_link(fs_info->fs_devices, src_device);

	btrfs_sysfs_update_devid(tgt_device);

	btrfs_rm_dev_replace_free_srcdev(src_device);



	/* write back the superblocks */

fs/btrfs/sysfs.c

+132 −23
Original line number Diff line number Diff line
@@ -1152,29 +1152,117 @@ int btrfs_sysfs_rm_device_link(struct btrfs_fs_devices *fs_devices, 
	if (!fs_devices->devices_kobj)

		return -EINVAL;



	if (one_device && one_device->bdev) {

	if (one_device) {

		if (one_device->bdev) {

			disk = one_device->bdev->bd_part;

			disk_kobj = &part_to_dev(disk)->kobj;



		sysfs_remove_link(fs_devices->devices_kobj, disk_kobj->name);

			sysfs_remove_link(fs_devices->devices_kobj,

					  disk_kobj->name);

		}



	if (one_device)

		kobject_del(&one_device->devid_kobj);

		kobject_put(&one_device->devid_kobj);



		wait_for_completion(&one_device->kobj_unregister);



		return 0;

	}



	list_for_each_entry(one_device,

			&fs_devices->devices, dev_list) {

		if (!one_device->bdev)

			continue;

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



		if (one_device->bdev) {

			disk = one_device->bdev->bd_part;

			disk_kobj = &part_to_dev(disk)->kobj;

			sysfs_remove_link(fs_devices->devices_kobj,

					  disk_kobj->name);

		}

		kobject_del(&one_device->devid_kobj);

		kobject_put(&one_device->devid_kobj);



		sysfs_remove_link(fs_devices->devices_kobj, disk_kobj->name);

		wait_for_completion(&one_device->kobj_unregister);

	}



	return 0;

}



static ssize_t btrfs_devinfo_in_fs_metadata_show(struct kobject *kobj,

					         struct kobj_attribute *a,

					         char *buf)

{

	int val;

	struct btrfs_device *device = container_of(kobj, struct btrfs_device,

						   devid_kobj);



	val = !!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);



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

}

BTRFS_ATTR(devid, in_fs_metadata, btrfs_devinfo_in_fs_metadata_show);



static ssize_t btrfs_sysfs_missing_show(struct kobject *kobj,

					struct kobj_attribute *a, char *buf)

{

	int val;

	struct btrfs_device *device = container_of(kobj, struct btrfs_device,

						   devid_kobj);



	val = !!test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);



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

}

BTRFS_ATTR(devid, missing, btrfs_sysfs_missing_show);



static ssize_t btrfs_devinfo_replace_target_show(struct kobject *kobj,

					         struct kobj_attribute *a,

					         char *buf)

{

	int val;

	struct btrfs_device *device = container_of(kobj, struct btrfs_device,

						   devid_kobj);



	val = !!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);



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

}

BTRFS_ATTR(devid, replace_target, btrfs_devinfo_replace_target_show);



static ssize_t btrfs_devinfo_writeable_show(struct kobject *kobj,

					    struct kobj_attribute *a, char *buf)

{

	int val;

	struct btrfs_device *device = container_of(kobj, struct btrfs_device,

						   devid_kobj);



	val = !!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);



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

}

BTRFS_ATTR(devid, writeable, btrfs_devinfo_writeable_show);



static struct attribute *devid_attrs[] = {

	BTRFS_ATTR_PTR(devid, in_fs_metadata),

	BTRFS_ATTR_PTR(devid, missing),

	BTRFS_ATTR_PTR(devid, replace_target),

	BTRFS_ATTR_PTR(devid, writeable),

	NULL

};

ATTRIBUTE_GROUPS(devid);



static void btrfs_release_devid_kobj(struct kobject *kobj)

{

	struct btrfs_device *device = container_of(kobj, struct btrfs_device,

						   devid_kobj);



	memset(&device->devid_kobj, 0, sizeof(struct kobject));

	complete(&device->kobj_unregister);

}



static struct kobj_type devid_ktype = {

	.sysfs_ops	= &kobj_sysfs_ops,

	.default_groups = devid_groups,

	.release	= btrfs_release_devid_kobj,

};



int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices,

				struct btrfs_device *one_device)

{
@@ -1182,15 +1270,14 @@ int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices, 
	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;



		if (dev->bdev) {

			struct hd_struct *disk;

			struct kobject *disk_kobj;



			disk = dev->bdev->bd_part;

			disk_kobj = &part_to_dev(disk)->kobj;
@@ -1200,6 +1287,16 @@ int btrfs_sysfs_add_device_link(struct btrfs_fs_devices *fs_devices, 
				break;

		}



		init_completion(&dev->kobj_unregister);

		error = kobject_init_and_add(&dev->devid_kobj, &devid_ktype,

					     fs_devices->devices_kobj, "%llu",

					     dev->devid);

		if (error) {

			kobject_put(&dev->devid_kobj);

			break;

		}

	}



	return error;

}
@@ -1229,6 +1326,18 @@ void btrfs_sysfs_update_sprout_fsid(struct btrfs_fs_devices *fs_devices, 
				"sysfs: failed to create fsid for sprout");

}



void btrfs_sysfs_update_devid(struct btrfs_device *device)

{

	char tmp[24];



	snprintf(tmp, sizeof(tmp), "%llu", device->devid);



	if (kobject_rename(&device->devid_kobj, tmp))

		btrfs_warn(device->fs_devices->fs_info,

			   "sysfs: failed to update devid for %llu",

			   device->devid);

}



/* /sys/fs/btrfs/ entry */

static struct kset *btrfs_kset;

fs/btrfs/sysfs.h

+1 −0
Original line number Diff line number Diff line
@@ -34,5 +34,6 @@ void btrfs_sysfs_add_block_group_type(struct btrfs_block_group *cache); 
int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info,

				    struct btrfs_space_info *space_info);

void btrfs_sysfs_remove_space_info(struct btrfs_space_info *space_info);

void btrfs_sysfs_update_devid(struct btrfs_device *device);



#endif

fs/btrfs/volumes.h

+4 −0
Original line number Diff line number Diff line
@@ -136,6 +136,10 @@ struct btrfs_device { 
	atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];



	struct extent_io_tree alloc_state;



	struct completion kobj_unregister;

	/* For sysfs/FSID/devinfo/devid/ */

	struct kobject devid_kobj;

};



/*

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