[v5,1/3] btrfs: Add unprivileged ioctl which returns subvolume information
diff mbox

Message ID 41f073796dcc50cb99eb325f6a224eaf2f37d449.1526446338.git.misono.tomohiro@jp.fujitsu.com
State New
Headers show

Commit Message

Misono Tomohiro May 16, 2018, 5:49 a.m. UTC
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.)

Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
---
 v4 -> v5
    - Update error handling of btrfs_next_leaf() to cover all cases
    - Return error if ROOT_BACKREF is not found (except top-level)

 fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/btrfs.h |  51 ++++++++++++++++
 2 files changed, 197 insertions(+)

Comments

Gu Jinxiang May 17, 2018, 6:11 a.m. UTC | #1
> -----Original Message-----

> From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-owner@vger.kernel.org] On Behalf Of Tomohiro Misono

> Sent: Wednesday, May 16, 2018 1:50 PM

> To: linux-btrfs@vger.kernel.org

> Subject: [PATCH v5 1/3] 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.)

> 

> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>

> ---

>  v4 -> v5

>     - Update error handling of btrfs_next_leaf() to cover all cases

>     - Return error if ROOT_BACKREF is not found (except top-level)

> 

>  fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++

>  include/uapi/linux/btrfs.h |  51 ++++++++++++++++

>  2 files changed, 197 insertions(+)

> 

> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 48e2ddff32bd..c1c9ae9a937d 100644

> --- a/fs/btrfs/ioctl.c

> +++ b/fs/btrfs/ioctl.c

> @@ -2242,6 +2242,150 @@ 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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,

> +					   void __user *argp)

> +{

> +	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;

> +	int slot;

> +

> +	unsigned long item_off;

> +	unsigned long item_len;

> +

> +	struct inode *inode;

> +	int ret;

> +

> +	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);

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

> +

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

> +	key.type = BTRFS_ROOT_ITEM_KEY;

> +	key.offset = 0;

> +

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

> +	if (ret < 0) {

> +		goto out;

> +	} else if (ret > 0) {

> +		u64 objectid = key.objectid;

> +

> +		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 = -ENOENT;

> +				goto out;

> +			}

> +		}

> +

> +		/* If the subvolume is a snapshot, offset is not zero */

> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);

> +		if (key.objectid != objectid ||

> +		    key.type != BTRFS_ROOT_ITEM_KEY) {

> +			ret = -ENOENT;

> +			goto out;

> +		}

> +	}

> +

> +	l = path->nodes[0];

> +	slot = path->slots[0];

> +	item_off = btrfs_item_ptr_offset(l, slot);

> +	item_len = btrfs_item_size_nr(l, slot);

> +	read_extent_buffer(l, &root_item, item_off, item_len);

> +

> +	subvol_info->id = 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);

> +

> +	btrfs_release_path(path);

> +	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {

> +		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 = -ENOENT;

> +				goto out;

> +			}

> +		}

> +

> +		l = path->nodes[0];

> +		slot = path->slots[0];

> +		btrfs_item_key_to_cpu(l, &key, slot);

> +		if (key.objectid == subvol_info->id &&

> +		    key.type == BTRFS_ROOT_BACKREF_KEY) {

> +			subvol_info->parent_id = key.offset;

> +

> +			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);

> +			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);

> +

> +			item_off = btrfs_item_ptr_offset(l, slot)

> +					+ sizeof(struct btrfs_root_ref);

> +			item_len = btrfs_item_size_nr(l, slot)

> +					- sizeof(struct btrfs_root_ref);

> +			read_extent_buffer(l, 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:

> +	kzfree(subvol_info);

> +	btrfs_free_path(path);

> +	return ret;

> +}

> +

>  static noinline int btrfs_ioctl_snap_destroy(struct file *file,

>  					     void __user *arg)

>  {

> @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int

>  		return btrfs_ioctl_get_features(file, argp);

>  	case BTRFS_IOC_SET_FEATURES:

>  		return btrfs_ioctl_set_features(file, argp);

> +	case BTRFS_IOC_GET_SUBVOL_INFO:

> +		return btrfs_ioctl_get_subvol_info(file, argp);

>  	}

> 

>  	return -ENOTTY;

> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index c8d99b9ca550..02cd1f1994e8 100644

> --- a/include/uapi/linux/btrfs.h

> +++ b/include/uapi/linux/btrfs.h

> @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args {

>  	__u64 reserved[4];		/* in */

>  };

> 

> +struct btrfs_ioctl_get_subvol_info_args {

> +	/* All field is out */

> +	/* Id of this subvolume */

> +	__u64 id;

> +	/* 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 deleted subvolume

> +	 */

> +	__u64 parent_id;

> +	/*

> +	 * Inode number of the directory which contains this subvolume.

> +	 * Zero for top-level subvolume or 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 non-snapshot subvolume

> +	 */

> +	__u8 parent_uuid[BTRFS_UUID_SIZE];

> +	/*

> +	 * uuid of the subvolume from which this subvolume is received.

> +	 * All zero for non-received subvolume

> +	 */

> +	__u8 received_uuid[BTRFS_UUID_SIZE];

> +

> +	/* Transaction id indicates when change/create/send/receive happens */

> +	__u64 ctransid;

> +	__u64 otransid;

> +	__u64 stransid;

> +	__u64 rtransid;

> +	/* Time corresponds 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;

> +

> +	__u64 reserved[8];

> +};

> +

>  /* Error codes as returned by the kernel */  enum btrfs_err_code {

>  	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1, @@ -843,5 +892,7 @@ 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 */

> --


Looks good to me.
Reviewed-by: Gu Jinxiang <gujx@cn.fujitsu.com>


Thks.
> 2.14.3

> 

> 

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>
Qu Wenruo May 17, 2018, 6:39 a.m. UTC | #2
On 2018年05月16日 13:49, Tomohiro Misono wrote:
> 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.)
> 
> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
> ---
>  v4 -> v5
>     - Update error handling of btrfs_next_leaf() to cover all cases
>     - Return error if ROOT_BACKREF is not found (except top-level)
> 
>  fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/btrfs.h |  51 ++++++++++++++++
>  2 files changed, 197 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 48e2ddff32bd..c1c9ae9a937d 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2242,6 +2242,150 @@ 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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,
> +					   void __user *argp)
> +{
> +	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;
> +	int slot;
> +
> +	unsigned long item_off;
> +	unsigned long item_len;
> +
> +	struct inode *inode;
> +	int ret;
> +
> +	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);
> +	root = BTRFS_I(inode)->root->fs_info->tree_root;
> +
> +	key.objectid = BTRFS_I(inode)->root->root_key.objectid;
> +	key.type = BTRFS_ROOT_ITEM_KEY;
> +	key.offset = 0;
> +
> +	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);

What about just using btrfs_get_fs_root()?

It would save several lines, and have better error handling along with
better tree cache.

Thanks,
Qu

> +	if (ret < 0) {
> +		goto out;
> +	} else if (ret > 0) {
> +		u64 objectid = key.objectid;
> +
> +		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 = -ENOENT;
> +				goto out;
> +			}
> +		}
> +
> +		/* If the subvolume is a snapshot, offset is not zero */
> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
> +		if (key.objectid != objectid ||
> +		    key.type != BTRFS_ROOT_ITEM_KEY) {
> +			ret = -ENOENT;
> +			goto out;
> +		}
> +	}
> +
> +	l = path->nodes[0];
> +	slot = path->slots[0];
> +	item_off = btrfs_item_ptr_offset(l, slot);
> +	item_len = btrfs_item_size_nr(l, slot);
> +	read_extent_buffer(l, &root_item, item_off, item_len);
> +
> +	subvol_info->id = 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);
> +
> +	btrfs_release_path(path);
> +	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {
> +		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 = -ENOENT;
> +				goto out;
> +			}
> +		}
> +
> +		l = path->nodes[0];
> +		slot = path->slots[0];
> +		btrfs_item_key_to_cpu(l, &key, slot);
> +		if (key.objectid == subvol_info->id &&
> +		    key.type == BTRFS_ROOT_BACKREF_KEY) {
> +			subvol_info->parent_id = key.offset;
> +
> +			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
> +			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);
> +
> +			item_off = btrfs_item_ptr_offset(l, slot)
> +					+ sizeof(struct btrfs_root_ref);
> +			item_len = btrfs_item_size_nr(l, slot)
> +					- sizeof(struct btrfs_root_ref);
> +			read_extent_buffer(l, 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:
> +	kzfree(subvol_info);
> +	btrfs_free_path(path);
> +	return ret;
> +}
> +
>  static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>  					     void __user *arg)
>  {
> @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>  		return btrfs_ioctl_get_features(file, argp);
>  	case BTRFS_IOC_SET_FEATURES:
>  		return btrfs_ioctl_set_features(file, argp);
> +	case BTRFS_IOC_GET_SUBVOL_INFO:
> +		return btrfs_ioctl_get_subvol_info(file, argp);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index c8d99b9ca550..02cd1f1994e8 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args {
>  	__u64 reserved[4];		/* in */
>  };
>  
> +struct btrfs_ioctl_get_subvol_info_args {
> +	/* All field is out */
> +	/* Id of this subvolume */
> +	__u64 id;
> +	/* 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 deleted subvolume
> +	 */
> +	__u64 parent_id;
> +	/*
> +	 * Inode number of the directory which contains this subvolume.
> +	 * Zero for top-level subvolume or 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 non-snapshot subvolume
> +	 */
> +	__u8 parent_uuid[BTRFS_UUID_SIZE];
> +	/*
> +	 * uuid of the subvolume from which this subvolume is received.
> +	 * All zero for non-received subvolume
> +	 */
> +	__u8 received_uuid[BTRFS_UUID_SIZE];
> +
> +	/* Transaction id indicates when change/create/send/receive happens */
> +	__u64 ctransid;
> +	__u64 otransid;
> +	__u64 stransid;
> +	__u64 rtransid;
> +	/* Time corresponds 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;
> +
> +	__u64 reserved[8];
> +};
> +
>  /* Error codes as returned by the kernel */
>  enum btrfs_err_code {
>  	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
> @@ -843,5 +892,7 @@ 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 */
>
Misono Tomohiro May 18, 2018, 1 a.m. UTC | #3
On 2018/05/17 15:39, Qu Wenruo wrote:
> 
> 
> On 2018年05月16日 13:49, Tomohiro Misono wrote:
>> 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.)
>>
>> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
>> ---
>>  v4 -> v5
>>     - Update error handling of btrfs_next_leaf() to cover all cases
>>     - Return error if ROOT_BACKREF is not found (except top-level)
>>
>>  fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/btrfs.h |  51 ++++++++++++++++
>>  2 files changed, 197 insertions(+)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index 48e2ddff32bd..c1c9ae9a937d 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -2242,6 +2242,150 @@ 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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,
>> +					   void __user *argp)
>> +{
>> +	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;
>> +	int slot;
>> +
>> +	unsigned long item_off;
>> +	unsigned long item_len;
>> +
>> +	struct inode *inode;
>> +	int ret;
>> +
>> +	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);
>> +	root = BTRFS_I(inode)->root->fs_info->tree_root;
>> +
>> +	key.objectid = BTRFS_I(inode)->root->root_key.objectid;
>> +	key.type = BTRFS_ROOT_ITEM_KEY;
>> +	key.offset = 0;
>> +
>> +	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
> 
> What about just using btrfs_get_fs_root()?
> 
> It would save several lines, and have better error handling along with
> better tree cache.

Here we search ROOT_ITEM of subvolume in root_tree and
I don't think btrfs_get_fs_root() would save lines, right?

Thanks,

> 
> Thanks,
> Qu
> 
>> +	if (ret < 0) {
>> +		goto out;
>> +	} else if (ret > 0) {
>> +		u64 objectid = key.objectid;
>> +
>> +		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 = -ENOENT;
>> +				goto out;
>> +			}
>> +		}
>> +
>> +		/* If the subvolume is a snapshot, offset is not zero */
>> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>> +		if (key.objectid != objectid ||
>> +		    key.type != BTRFS_ROOT_ITEM_KEY) {
>> +			ret = -ENOENT;
>> +			goto out;
>> +		}
>> +	}
>> +
>> +	l = path->nodes[0];
>> +	slot = path->slots[0];
>> +	item_off = btrfs_item_ptr_offset(l, slot);
>> +	item_len = btrfs_item_size_nr(l, slot);
>> +	read_extent_buffer(l, &root_item, item_off, item_len);
>> +
>> +	subvol_info->id = 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);
>> +
>> +	btrfs_release_path(path);
>> +	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {
>> +		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 = -ENOENT;
>> +				goto out;
>> +			}
>> +		}
>> +
>> +		l = path->nodes[0];
>> +		slot = path->slots[0];
>> +		btrfs_item_key_to_cpu(l, &key, slot);
>> +		if (key.objectid == subvol_info->id &&
>> +		    key.type == BTRFS_ROOT_BACKREF_KEY) {
>> +			subvol_info->parent_id = key.offset;
>> +
>> +			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
>> +			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);
>> +
>> +			item_off = btrfs_item_ptr_offset(l, slot)
>> +					+ sizeof(struct btrfs_root_ref);
>> +			item_len = btrfs_item_size_nr(l, slot)
>> +					- sizeof(struct btrfs_root_ref);
>> +			read_extent_buffer(l, 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:
>> +	kzfree(subvol_info);
>> +	btrfs_free_path(path);
>> +	return ret;
>> +}
>> +
>>  static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>>  					     void __user *arg)
>>  {
>> @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>  		return btrfs_ioctl_get_features(file, argp);
>>  	case BTRFS_IOC_SET_FEATURES:
>>  		return btrfs_ioctl_set_features(file, argp);
>> +	case BTRFS_IOC_GET_SUBVOL_INFO:
>> +		return btrfs_ioctl_get_subvol_info(file, argp);
>>  	}
>>  
>>  	return -ENOTTY;
>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>> index c8d99b9ca550..02cd1f1994e8 100644
>> --- a/include/uapi/linux/btrfs.h
>> +++ b/include/uapi/linux/btrfs.h
>> @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args {
>>  	__u64 reserved[4];		/* in */
>>  };
>>  
>> +struct btrfs_ioctl_get_subvol_info_args {
>> +	/* All field is out */
>> +	/* Id of this subvolume */
>> +	__u64 id;
>> +	/* 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 deleted subvolume
>> +	 */
>> +	__u64 parent_id;
>> +	/*
>> +	 * Inode number of the directory which contains this subvolume.
>> +	 * Zero for top-level subvolume or 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 non-snapshot subvolume
>> +	 */
>> +	__u8 parent_uuid[BTRFS_UUID_SIZE];
>> +	/*
>> +	 * uuid of the subvolume from which this subvolume is received.
>> +	 * All zero for non-received subvolume
>> +	 */
>> +	__u8 received_uuid[BTRFS_UUID_SIZE];
>> +
>> +	/* Transaction id indicates when change/create/send/receive happens */
>> +	__u64 ctransid;
>> +	__u64 otransid;
>> +	__u64 stransid;
>> +	__u64 rtransid;
>> +	/* Time corresponds 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;
>> +
>> +	__u64 reserved[8];
>> +};
>> +
>>  /* Error codes as returned by the kernel */
>>  enum btrfs_err_code {
>>  	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
>> @@ -843,5 +892,7 @@ 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 */
>>
> 

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Qu Wenruo May 18, 2018, 1:10 a.m. UTC | #4
On 2018年05月18日 09:00, Misono Tomohiro wrote:
> On 2018/05/17 15:39, Qu Wenruo wrote:
>>
>>
>> On 2018年05月16日 13:49, Tomohiro Misono wrote:
>>> 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.)
>>>
>>> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
>>> ---
>>>  v4 -> v5
>>>     - Update error handling of btrfs_next_leaf() to cover all cases
>>>     - Return error if ROOT_BACKREF is not found (except top-level)
>>>
>>>  fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++
>>>  include/uapi/linux/btrfs.h |  51 ++++++++++++++++
>>>  2 files changed, 197 insertions(+)
>>>
>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>>> index 48e2ddff32bd..c1c9ae9a937d 100644
>>> --- a/fs/btrfs/ioctl.c
>>> +++ b/fs/btrfs/ioctl.c
>>> @@ -2242,6 +2242,150 @@ 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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,
>>> +					   void __user *argp)
>>> +{
>>> +	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;
>>> +	int slot;
>>> +
>>> +	unsigned long item_off;
>>> +	unsigned long item_len;
>>> +
>>> +	struct inode *inode;
>>> +	int ret;
>>> +
>>> +	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);
>>> +	root = BTRFS_I(inode)->root->fs_info->tree_root;
>>> +
>>> +	key.objectid = BTRFS_I(inode)->root->root_key.objectid;
>>> +	key.type = BTRFS_ROOT_ITEM_KEY;
>>> +	key.offset = 0;
>>> +
>>> +	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
>>
>> What about just using btrfs_get_fs_root()?
>>
>> It would save several lines, and have better error handling along with
>> better tree cache.
> 
> Here we search ROOT_ITEM of subvolume in root_tree and
> I don't think btrfs_get_fs_root() would save lines, right?

btrfs_root has root_item member.

So just btrfs_get_fs_root(), then use root->root_item.


>>> +	if (ret < 0) {
>>> +		goto out;
>>> +	} else if (ret > 0) {
>>> +		u64 objectid = key.objectid;
>>> +
>>> +		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 = -ENOENT;
>>> +				goto out;
>>> +			}
>>> +		}
>>> +
>>> +		/* If the subvolume is a snapshot, offset is not zero */
>>> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>>> +		if (key.objectid != objectid ||
>>> +		    key.type != BTRFS_ROOT_ITEM_KEY) {
>>> +			ret = -ENOENT;
>>> +			goto out;
>>> +		}
>>> +	}

These lines can be saved.

Thanks,
Qu

>>> +	l = path->nodes[0];
>>> +	slot = path->slots[0];
>>> +	item_off = btrfs_item_ptr_offset(l, slot);
>>> +	item_len = btrfs_item_size_nr(l, slot);
>>> +	read_extent_buffer(l, &root_item, item_off, item_len);
>>> +
>>> +	subvol_info->id = 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);
>>> +
>>> +	btrfs_release_path(path);
>>> +	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {
>>> +		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 = -ENOENT;
>>> +				goto out;
>>> +			}
>>> +		}
>>> +
>>> +		l = path->nodes[0];
>>> +		slot = path->slots[0];
>>> +		btrfs_item_key_to_cpu(l, &key, slot);
>>> +		if (key.objectid == subvol_info->id &&
>>> +		    key.type == BTRFS_ROOT_BACKREF_KEY) {
>>> +			subvol_info->parent_id = key.offset;
>>> +
>>> +			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
>>> +			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);
>>> +
>>> +			item_off = btrfs_item_ptr_offset(l, slot)
>>> +					+ sizeof(struct btrfs_root_ref);
>>> +			item_len = btrfs_item_size_nr(l, slot)
>>> +					- sizeof(struct btrfs_root_ref);
>>> +			read_extent_buffer(l, 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:
>>> +	kzfree(subvol_info);
>>> +	btrfs_free_path(path);
>>> +	return ret;
>>> +}
>>> +
>>>  static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>>>  					     void __user *arg)
>>>  {
>>> @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>>  		return btrfs_ioctl_get_features(file, argp);
>>>  	case BTRFS_IOC_SET_FEATURES:
>>>  		return btrfs_ioctl_set_features(file, argp);
>>> +	case BTRFS_IOC_GET_SUBVOL_INFO:
>>> +		return btrfs_ioctl_get_subvol_info(file, argp);
>>>  	}
>>>  
>>>  	return -ENOTTY;
>>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>>> index c8d99b9ca550..02cd1f1994e8 100644
>>> --- a/include/uapi/linux/btrfs.h
>>> +++ b/include/uapi/linux/btrfs.h
>>> @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args {
>>>  	__u64 reserved[4];		/* in */
>>>  };
>>>  
>>> +struct btrfs_ioctl_get_subvol_info_args {
>>> +	/* All field is out */
>>> +	/* Id of this subvolume */
>>> +	__u64 id;
>>> +	/* 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 deleted subvolume
>>> +	 */
>>> +	__u64 parent_id;
>>> +	/*
>>> +	 * Inode number of the directory which contains this subvolume.
>>> +	 * Zero for top-level subvolume or 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 non-snapshot subvolume
>>> +	 */
>>> +	__u8 parent_uuid[BTRFS_UUID_SIZE];
>>> +	/*
>>> +	 * uuid of the subvolume from which this subvolume is received.
>>> +	 * All zero for non-received subvolume
>>> +	 */
>>> +	__u8 received_uuid[BTRFS_UUID_SIZE];
>>> +
>>> +	/* Transaction id indicates when change/create/send/receive happens */
>>> +	__u64 ctransid;
>>> +	__u64 otransid;
>>> +	__u64 stransid;
>>> +	__u64 rtransid;
>>> +	/* Time corresponds 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;
>>> +
>>> +	__u64 reserved[8];
>>> +};
>>> +
>>>  /* Error codes as returned by the kernel */
>>>  enum btrfs_err_code {
>>>  	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
>>> @@ -843,5 +892,7 @@ 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 */
>>>
>>
>
Misono Tomohiro May 18, 2018, 1:37 a.m. UTC | #5
On 2018/05/18 10:10, Qu Wenruo wrote:
> 
> 
> On 2018年05月18日 09:00, Misono Tomohiro wrote:
>> On 2018/05/17 15:39, Qu Wenruo wrote:
>>>
>>>
>>> On 2018年05月16日 13:49, Tomohiro Misono wrote:
>>>> 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.)
>>>>
>>>> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
>>>> ---
>>>>  v4 -> v5
>>>>     - Update error handling of btrfs_next_leaf() to cover all cases
>>>>     - Return error if ROOT_BACKREF is not found (except top-level)
>>>>
>>>>  fs/btrfs/ioctl.c           | 146 +++++++++++++++++++++++++++++++++++++++++++++
>>>>  include/uapi/linux/btrfs.h |  51 ++++++++++++++++
>>>>  2 files changed, 197 insertions(+)
>>>>
>>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>>>> index 48e2ddff32bd..c1c9ae9a937d 100644
>>>> --- a/fs/btrfs/ioctl.c
>>>> +++ b/fs/btrfs/ioctl.c
>>>> @@ -2242,6 +2242,150 @@ 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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,
>>>> +					   void __user *argp)
>>>> +{
>>>> +	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;
>>>> +	int slot;
>>>> +
>>>> +	unsigned long item_off;
>>>> +	unsigned long item_len;
>>>> +
>>>> +	struct inode *inode;
>>>> +	int ret;
>>>> +
>>>> +	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);
>>>> +	root = BTRFS_I(inode)->root->fs_info->tree_root;
>>>> +
>>>> +	key.objectid = BTRFS_I(inode)->root->root_key.objectid;
>>>> +	key.type = BTRFS_ROOT_ITEM_KEY;
>>>> +	key.offset = 0;
>>>> +
>>>> +	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
>>>
>>> What about just using btrfs_get_fs_root()?
>>>
>>> It would save several lines, and have better error handling along with
>>> better tree cache.
>>
>> Here we search ROOT_ITEM of subvolume in root_tree and
>> I don't think btrfs_get_fs_root() would save lines, right?
> 
> btrfs_root has root_item member.
> 
> So just btrfs_get_fs_root(), then use root->root_item.

Ok, I see. Thanks for you kind help.

> 
> 
>>>> +	if (ret < 0) {
>>>> +		goto out;
>>>> +	} else if (ret > 0) {
>>>> +		u64 objectid = key.objectid;
>>>> +
>>>> +		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 = -ENOENT;
>>>> +				goto out;
>>>> +			}
>>>> +		}
>>>> +
>>>> +		/* If the subvolume is a snapshot, offset is not zero */
>>>> +		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>>>> +		if (key.objectid != objectid ||
>>>> +		    key.type != BTRFS_ROOT_ITEM_KEY) {
>>>> +			ret = -ENOENT;
>>>> +			goto out;
>>>> +		}
>>>> +	}
> 
> These lines can be saved.
> 
> Thanks,
> Qu
> 
>>>> +	l = path->nodes[0];
>>>> +	slot = path->slots[0];
>>>> +	item_off = btrfs_item_ptr_offset(l, slot);
>>>> +	item_len = btrfs_item_size_nr(l, slot);
>>>> +	read_extent_buffer(l, &root_item, item_off, item_len);
>>>> +
>>>> +	subvol_info->id = 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);
>>>> +
>>>> +	btrfs_release_path(path);
>>>> +	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {
>>>> +		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 = -ENOENT;
>>>> +				goto out;
>>>> +			}
>>>> +		}
>>>> +
>>>> +		l = path->nodes[0];
>>>> +		slot = path->slots[0];
>>>> +		btrfs_item_key_to_cpu(l, &key, slot);
>>>> +		if (key.objectid == subvol_info->id &&
>>>> +		    key.type == BTRFS_ROOT_BACKREF_KEY) {
>>>> +			subvol_info->parent_id = key.offset;
>>>> +
>>>> +			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
>>>> +			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);
>>>> +
>>>> +			item_off = btrfs_item_ptr_offset(l, slot)
>>>> +					+ sizeof(struct btrfs_root_ref);
>>>> +			item_len = btrfs_item_size_nr(l, slot)
>>>> +					- sizeof(struct btrfs_root_ref);
>>>> +			read_extent_buffer(l, 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:
>>>> +	kzfree(subvol_info);
>>>> +	btrfs_free_path(path);
>>>> +	return ret;
>>>> +}
>>>> +
>>>>  static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>>>>  					     void __user *arg)
>>>>  {
>>>> @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>>>  		return btrfs_ioctl_get_features(file, argp);
>>>>  	case BTRFS_IOC_SET_FEATURES:
>>>>  		return btrfs_ioctl_set_features(file, argp);
>>>> +	case BTRFS_IOC_GET_SUBVOL_INFO:
>>>> +		return btrfs_ioctl_get_subvol_info(file, argp);
>>>>  	}
>>>>  
>>>>  	return -ENOTTY;
>>>> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
>>>> index c8d99b9ca550..02cd1f1994e8 100644
>>>> --- a/include/uapi/linux/btrfs.h
>>>> +++ b/include/uapi/linux/btrfs.h
>>>> @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args {
>>>>  	__u64 reserved[4];		/* in */
>>>>  };
>>>>  
>>>> +struct btrfs_ioctl_get_subvol_info_args {
>>>> +	/* All field is out */
>>>> +	/* Id of this subvolume */
>>>> +	__u64 id;
>>>> +	/* 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 deleted subvolume
>>>> +	 */
>>>> +	__u64 parent_id;
>>>> +	/*
>>>> +	 * Inode number of the directory which contains this subvolume.
>>>> +	 * Zero for top-level subvolume or 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 non-snapshot subvolume
>>>> +	 */
>>>> +	__u8 parent_uuid[BTRFS_UUID_SIZE];
>>>> +	/*
>>>> +	 * uuid of the subvolume from which this subvolume is received.
>>>> +	 * All zero for non-received subvolume
>>>> +	 */
>>>> +	__u8 received_uuid[BTRFS_UUID_SIZE];
>>>> +
>>>> +	/* Transaction id indicates when change/create/send/receive happens */
>>>> +	__u64 ctransid;
>>>> +	__u64 otransid;
>>>> +	__u64 stransid;
>>>> +	__u64 rtransid;
>>>> +	/* Time corresponds 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;
>>>> +
>>>> +	__u64 reserved[8];
>>>> +};
>>>> +
>>>>  /* Error codes as returned by the kernel */
>>>>  enum btrfs_err_code {
>>>>  	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
>>>> @@ -843,5 +892,7 @@ 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 */
>>>>
>>>
>>
> 

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Patch
diff mbox

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 48e2ddff32bd..c1c9ae9a937d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2242,6 +2242,150 @@  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 noinline int btrfs_ioctl_get_subvol_info(struct file *file,
+					   void __user *argp)
+{
+	struct btrfs_ioctl_get_subvol_info_args *subvol_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 *l;
+	int slot;
+
+	unsigned long item_off;
+	unsigned long item_len;
+
+	struct inode *inode;
+	int ret;
+
+	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);
+	root = BTRFS_I(inode)->root->fs_info->tree_root;
+
+	key.objectid = BTRFS_I(inode)->root->root_key.objectid;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0) {
+		goto out;
+	} else if (ret > 0) {
+		u64 objectid = key.objectid;
+
+		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 = -ENOENT;
+				goto out;
+			}
+		}
+
+		/* If the subvolume is a snapshot, offset is not zero */
+		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+		if (key.objectid != objectid ||
+		    key.type != BTRFS_ROOT_ITEM_KEY) {
+			ret = -ENOENT;
+			goto out;
+		}
+	}
+
+	l = path->nodes[0];
+	slot = path->slots[0];
+	item_off = btrfs_item_ptr_offset(l, slot);
+	item_len = btrfs_item_size_nr(l, slot);
+	read_extent_buffer(l, &root_item, item_off, item_len);
+
+	subvol_info->id = 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);
+
+	btrfs_release_path(path);
+	if (key.objectid != BTRFS_FS_TREE_OBJECTID) {
+		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 = -ENOENT;
+				goto out;
+			}
+		}
+
+		l = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(l, &key, slot);
+		if (key.objectid == subvol_info->id &&
+		    key.type == BTRFS_ROOT_BACKREF_KEY) {
+			subvol_info->parent_id = key.offset;
+
+			rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
+			subvol_info->dirid = btrfs_root_ref_dirid(l, rref);
+
+			item_off = btrfs_item_ptr_offset(l, slot)
+					+ sizeof(struct btrfs_root_ref);
+			item_len = btrfs_item_size_nr(l, slot)
+					- sizeof(struct btrfs_root_ref);
+			read_extent_buffer(l, 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:
+	kzfree(subvol_info);
+	btrfs_free_path(path);
+	return ret;
+}
+
 static noinline int btrfs_ioctl_snap_destroy(struct file *file,
 					     void __user *arg)
 {
@@ -5374,6 +5518,8 @@  long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_get_features(file, argp);
 	case BTRFS_IOC_SET_FEATURES:
 		return btrfs_ioctl_set_features(file, argp);
+	case BTRFS_IOC_GET_SUBVOL_INFO:
+		return btrfs_ioctl_get_subvol_info(file, argp);
 	}
 
 	return -ENOTTY;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index c8d99b9ca550..02cd1f1994e8 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -725,6 +725,55 @@  struct btrfs_ioctl_send_args {
 	__u64 reserved[4];		/* in */
 };
 
+struct btrfs_ioctl_get_subvol_info_args {
+	/* All field is out */
+	/* Id of this subvolume */
+	__u64 id;
+	/* 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 deleted subvolume
+	 */
+	__u64 parent_id;
+	/*
+	 * Inode number of the directory which contains this subvolume.
+	 * Zero for top-level subvolume or 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 non-snapshot subvolume
+	 */
+	__u8 parent_uuid[BTRFS_UUID_SIZE];
+	/*
+	 * uuid of the subvolume from which this subvolume is received.
+	 * All zero for non-received subvolume
+	 */
+	__u8 received_uuid[BTRFS_UUID_SIZE];
+
+	/* Transaction id indicates when change/create/send/receive happens */
+	__u64 ctransid;
+	__u64 otransid;
+	__u64 stransid;
+	__u64 rtransid;
+	/* Time corresponds 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;
+
+	__u64 reserved[8];
+};
+
 /* Error codes as returned by the kernel */
 enum btrfs_err_code {
 	BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1,
@@ -843,5 +892,7 @@  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 */