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Subject[PATCH 2/2] btrfs: Introduce new BTRFS_IOC_SNAP_DESTROY_V2 ioctl
Date
From: Marcos Paulo de Souza <mpdesouza@suse.com>

This ioctl will be responsible for deleting a subvolume using it's id.
This can be used when a system has a file system mounted from a
subvolume, rather than the root file system, like below:

/
|- @subvol1
|- @subvol2
\- @subvol_default
If only @subvol_default is mounted, we have no path to reach
@subvol1 and @subvol2, thus no way to delete them.
This patch introduces a new flag to allow BTRFS_IOC_SNAP_DESTORY_V2
to delete subvolume using subvolid.

Also in this patch, add BTRFS_SUBVOL_DELETE_BY_ID flag and add subvolid
as a union member of fd in struct btrfs_ioctl_vol_args_v2.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
fs/btrfs/ctree.h | 8 ++++++
fs/btrfs/export.c | 4 +--
fs/btrfs/ioctl.c | 53 ++++++++++++++++++++++++++++++++++++++
fs/btrfs/super.c | 2 +-
include/uapi/linux/btrfs.h | 12 +++++++--
5 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 569931dd0ce5..421a2f57f9ec 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3010,6 +3010,8 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
unsigned long new_flags);
int btrfs_sync_fs(struct super_block *sb, int wait);
+char *get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
+ u64 subvol_objectid);

static inline __printf(2, 3) __cold
void btrfs_no_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
@@ -3442,6 +3444,12 @@ int btrfs_reada_wait(void *handle);
void btrfs_reada_detach(void *handle);
int btree_readahead_hook(struct extent_buffer *eb, int err);

+/* export.c */
+struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
+ u64 root_objectid, u32 generation,
+ int check_generation);
+struct dentry *btrfs_get_parent(struct dentry *child);
+
static inline int is_fstree(u64 rootid)
{
if (rootid == BTRFS_FS_TREE_OBJECTID ||
diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 72e312cae69d..027411cdbae7 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -57,7 +57,7 @@ static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
return type;
}

-static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
+struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
u64 root_objectid, u32 generation,
int check_generation)
{
@@ -152,7 +152,7 @@ static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);
}

-static struct dentry *btrfs_get_parent(struct dentry *child)
+struct dentry *btrfs_get_parent(struct dentry *child)
{
struct inode *dir = d_inode(child);
struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index dcceae4c5d28..68da45ad4904 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2960,6 +2960,57 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
return err;
}

+static noinline int btrfs_ioctl_snap_destroy_v2(struct file *file,
+ void __user *arg)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(file->f_path.dentry->d_sb);
+ struct dentry *dentry, *pdentry;
+ struct btrfs_ioctl_vol_args_v2 *vol_args;
+ char *name, *p;
+ size_t namelen;
+ int err = 0;
+
+ vol_args = memdup_user(arg, sizeof(*vol_args));
+ if (IS_ERR(vol_args))
+ return PTR_ERR(vol_args);
+
+ if (vol_args->subvolid == 0)
+ return -EINVAL;
+
+ if (!(vol_args->flags & BTRFS_SUBVOL_DELETE_BY_ID))
+ return -EINVAL;
+
+ dentry = btrfs_get_dentry(fs_info->sb, BTRFS_FIRST_FREE_OBJECTID,
+ vol_args->subvolid, 0, 0);
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ return err;
+ }
+
+ pdentry = btrfs_get_parent(dentry);
+ if (IS_ERR(pdentry)) {
+ err = PTR_ERR(pdentry);
+ goto out_dentry;
+ }
+
+ name = get_subvol_name_from_objectid(fs_info, vol_args->subvolid);
+ if (IS_ERR(name)) {
+ err = PTR_ERR(name);
+ goto out_pdentry;
+ }
+ p = (char *)kbasename(name);
+ namelen = strlen(p);
+
+ err = btrfs_subvolume_deleter(file, pdentry, p, namelen);
+
+ kfree(name);
+out_pdentry:
+ dput(pdentry);
+out_dentry:
+ dput(dentry);
+ return err;
+}
+
static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
{
struct inode *inode = file_inode(file);
@@ -5465,6 +5516,8 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_snap_create_v2(file, argp, 1);
case BTRFS_IOC_SNAP_DESTROY:
return btrfs_ioctl_snap_destroy(file, argp);
+ case BTRFS_IOC_SNAP_DESTROY_V2:
+ return btrfs_ioctl_snap_destroy_v2(file, argp);
case BTRFS_IOC_SUBVOL_GETFLAGS:
return btrfs_ioctl_subvol_getflags(file, argp);
case BTRFS_IOC_SUBVOL_SETFLAGS:
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a906315efd19..a448d2bb93e6 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1024,7 +1024,7 @@ static int btrfs_parse_subvol_options(const char *options, char **subvol_name,
return error;
}

-static char *get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
+char *get_subvol_name_from_objectid(struct btrfs_fs_info *fs_info,
u64 subvol_objectid)
{
struct btrfs_root *root = fs_info->tree_root;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 7a8bc8b920f5..1be03082e49a 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -42,11 +42,14 @@ struct btrfs_ioctl_vol_args {

#define BTRFS_DEVICE_SPEC_BY_ID (1ULL << 3)

+#define BTRFS_SUBVOL_DELETE_BY_ID (1ULL << 4)
+
#define BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED \
(BTRFS_SUBVOL_CREATE_ASYNC | \
BTRFS_SUBVOL_RDONLY | \
BTRFS_SUBVOL_QGROUP_INHERIT | \
- BTRFS_DEVICE_SPEC_BY_ID)
+ BTRFS_DEVICE_SPEC_BY_ID | \
+ BTRFS_SUBVOL_DELETE_BY_ID)

#define BTRFS_FSID_SIZE 16
#define BTRFS_UUID_SIZE 16
@@ -108,7 +111,10 @@ struct btrfs_ioctl_qgroup_limit_args {
*/

struct btrfs_ioctl_vol_args_v2 {
- __s64 fd;
+ union {
+ __s64 fd;
+ __u64 subvolid;
+ };
__u64 transid;
__u64 flags;
union {
@@ -949,5 +955,7 @@ enum btrfs_err_code {
struct btrfs_ioctl_get_subvol_rootref_args)
#define BTRFS_IOC_INO_LOOKUP_USER _IOWR(BTRFS_IOCTL_MAGIC, 62, \
struct btrfs_ioctl_ino_lookup_user_args)
+#define BTRFS_IOC_SNAP_DESTROY_V2 _IOW(BTRFS_IOCTL_MAGIC, 63, \
+ struct btrfs_ioctl_vol_args_v2)

#endif /* _UAPI_LINUX_BTRFS_H */
--
2.24.0
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