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Commit b64ec075 authored by Tomohiro Misono's avatar Tomohiro Misono Committed by David Sterba
Browse files

btrfs: Add unprivileged ioctl which returns subvolume information 



Add new unprivileged ioctl BTRFS_IOC_GET_SUBVOL_INFO which returns
the information of subvolume containing this inode.
(i.e. returns the information in ROOT_ITEM and ROOT_BACKREF.)

Reviewed-by: default avatarGu Jinxiang <gujx@cn.fujitsu.com>
Tested-by: default avatarGu Jinxiang <gujx@cn.fujitsu.com>
Signed-off-by: default avatarTomohiro Misono <misono.tomohiro@jp.fujitsu.com>
[ minor style fixes, update struct comments ]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ad7e1a74

fs/btrfs/ioctl.c

+121 −0
Original line number Diff line number Diff line
@@ -2383,6 +2383,125 @@ static noinline int btrfs_ioctl_ino_lookup(struct file *file, 
	return ret;

}



/* Get the subvolume information in BTRFS_ROOT_ITEM and BTRFS_ROOT_BACKREF */

static int btrfs_ioctl_get_subvol_info(struct file *file, void __user *argp)

{

	struct btrfs_ioctl_get_subvol_info_args *subvol_info;

	struct btrfs_fs_info *fs_info;

	struct btrfs_root *root;

	struct btrfs_path *path;

	struct btrfs_key key;

	struct btrfs_root_item *root_item;

	struct btrfs_root_ref *rref;

	struct extent_buffer *leaf;

	unsigned long item_off;

	unsigned long item_len;

	struct inode *inode;

	int slot;

	int ret = 0;



	path = btrfs_alloc_path();

	if (!path)

		return -ENOMEM;



	subvol_info = kzalloc(sizeof(*subvol_info), GFP_KERNEL);

	if (!subvol_info) {

		btrfs_free_path(path);

		return -ENOMEM;

	}



	inode = file_inode(file);

	fs_info = BTRFS_I(inode)->root->fs_info;



	/* Get root_item of inode's subvolume */

	key.objectid = BTRFS_I(inode)->root->root_key.objectid;

	key.type = BTRFS_ROOT_ITEM_KEY;

	key.offset = (u64)-1;

	root = btrfs_read_fs_root_no_name(fs_info, &key);

	if (IS_ERR(root)) {

		ret = PTR_ERR(root);

		goto out;

	}

	root_item = &root->root_item;



	subvol_info->treeid = key.objectid;



	subvol_info->generation = btrfs_root_generation(root_item);

	subvol_info->flags = btrfs_root_flags(root_item);



	memcpy(subvol_info->uuid, root_item->uuid, BTRFS_UUID_SIZE);

	memcpy(subvol_info->parent_uuid, root_item->parent_uuid,

						    BTRFS_UUID_SIZE);

	memcpy(subvol_info->received_uuid, root_item->received_uuid,

						    BTRFS_UUID_SIZE);



	subvol_info->ctransid = btrfs_root_ctransid(root_item);

	subvol_info->ctime.sec = btrfs_stack_timespec_sec(&root_item->ctime);

	subvol_info->ctime.nsec = btrfs_stack_timespec_nsec(&root_item->ctime);



	subvol_info->otransid = btrfs_root_otransid(root_item);

	subvol_info->otime.sec = btrfs_stack_timespec_sec(&root_item->otime);

	subvol_info->otime.nsec = btrfs_stack_timespec_nsec(&root_item->otime);



	subvol_info->stransid = btrfs_root_stransid(root_item);

	subvol_info->stime.sec = btrfs_stack_timespec_sec(&root_item->stime);

	subvol_info->stime.nsec = btrfs_stack_timespec_nsec(&root_item->stime);



	subvol_info->rtransid = btrfs_root_rtransid(root_item);

	subvol_info->rtime.sec = btrfs_stack_timespec_sec(&root_item->rtime);

	subvol_info->rtime.nsec = btrfs_stack_timespec_nsec(&root_item->rtime);



	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {

		/* Search root tree for ROOT_BACKREF of this subvolume */

		root = fs_info->tree_root;



		key.type = BTRFS_ROOT_BACKREF_KEY;

		key.offset = 0;

		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);

		if (ret < 0) {

			goto out;

		} else if (path->slots[0] >=

			   btrfs_header_nritems(path->nodes[0])) {

			ret = btrfs_next_leaf(root, path);

			if (ret < 0) {

				goto out;

			} else if (ret > 0) {

				ret = -EUCLEAN;

				goto out;

			}

		}



		leaf = path->nodes[0];

		slot = path->slots[0];

		btrfs_item_key_to_cpu(leaf, &key, slot);

		if (key.objectid == subvol_info->treeid &&

		    key.type == BTRFS_ROOT_BACKREF_KEY) {

			subvol_info->parent_id = key.offset;



			rref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref);

			subvol_info->dirid = btrfs_root_ref_dirid(leaf, rref);



			item_off = btrfs_item_ptr_offset(leaf, slot)

					+ sizeof(struct btrfs_root_ref);

			item_len = btrfs_item_size_nr(leaf, slot)

					- sizeof(struct btrfs_root_ref);

			read_extent_buffer(leaf, subvol_info->name,

					   item_off, item_len);

		} else {

			ret = -ENOENT;

			goto out;

		}

	}



	if (copy_to_user(argp, subvol_info, sizeof(*subvol_info)))

		ret = -EFAULT;



out:

	btrfs_free_path(path);

	kzfree(subvol_info);

	return ret;

}



static noinline int btrfs_ioctl_snap_destroy(struct file *file,

					     void __user *arg)

{
@@ -5545,6 +5664,8 @@ long btrfs_ioctl(struct file *file, unsigned int 
		return btrfs_ioctl_fsgetxattr(file, argp);

	case FS_IOC_FSSETXATTR:

		return btrfs_ioctl_fssetxattr(file, argp);

	case BTRFS_IOC_GET_SUBVOL_INFO:

		return btrfs_ioctl_get_subvol_info(file, argp);

	}



	return -ENOTTY;

include/uapi/linux/btrfs.h

+62 −0
Original line number Diff line number Diff line
@@ -725,6 +725,66 @@ struct btrfs_ioctl_send_args { 
	__u64 reserved[4];		/* in */

};



/*

 * Information about a fs tree root.

 *

 * All items are filled by the ioctl

 */

struct btrfs_ioctl_get_subvol_info_args {

	/* Id of this subvolume */

	__u64 treeid;



	/* Name of this subvolume, used to get the real name at mount point */

	char name[BTRFS_VOL_NAME_MAX + 1];



	/*

	 * Id of the subvolume which contains this subvolume.

	 * Zero for top-level subvolume or a deleted subvolume.

	 */

	__u64 parent_id;



	/*

	 * Inode number of the directory which contains this subvolume.

	 * Zero for top-level subvolume or a deleted subvolume

	 */

	__u64 dirid;



	/* Latest transaction id of this subvolume */

	__u64 generation;



	/* Flags of this subvolume */

	__u64 flags;



	/* UUID of this subvolume */

	__u8 uuid[BTRFS_UUID_SIZE];



	/*

	 * UUID of the subvolume of which this subvolume is a snapshot.

	 * All zero for a non-snapshot subvolume.

	 */

	__u8 parent_uuid[BTRFS_UUID_SIZE];



	/*

	 * UUID of the subvolume from which this subvolume was received.

	 * All zero for non-received subvolume.

	 */

	__u8 received_uuid[BTRFS_UUID_SIZE];



	/* Transaction id indicating when change/create/send/receive happened */

	__u64 ctransid;

	__u64 otransid;

	__u64 stransid;

	__u64 rtransid;

	/* Time corresponding to c/o/s/rtransid */

	struct btrfs_ioctl_timespec ctime;

	struct btrfs_ioctl_timespec otime;

	struct btrfs_ioctl_timespec stime;

	struct btrfs_ioctl_timespec rtime;



	/* Must be zero */

	__u64 reserved[8];

};



/* Error codes as returned by the kernel */

enum btrfs_err_code {

	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
@@ -843,5 +903,7 @@ enum btrfs_err_code { 
				   struct btrfs_ioctl_vol_args_v2)

#define BTRFS_IOC_LOGICAL_INO_V2 _IOWR(BTRFS_IOCTL_MAGIC, 59, \

					struct btrfs_ioctl_logical_ino_args)

#define BTRFS_IOC_GET_SUBVOL_INFO _IOR(BTRFS_IOCTL_MAGIC, 60, \

				struct btrfs_ioctl_get_subvol_info_args)



#endif /* _UAPI_LINUX_BTRFS_H */