[PATCH] btrfs: add an ioctl to force chunk allocation

[Josef Bacik]

In testing block group removal it's sometimes handy to be able to create
block groups on demand.  Add an ioctl to allow us to force allocation
from userspace.

Signed-off-by: Josef Bacik <jo...@toxicpanda.com>
---
 fs/btrfs/ioctl.c           | 30 ++++++++++++++++++++++++++++++
 include/uapi/linux/btrfs.h |  1 +
 2 files changed, 31 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d0743ec1231d..f100def53c29 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5553,6 +5553,34 @@ static int _btrfs_ioctl_send(struct file *file, void 
__user *argp, bool compat)
        return ret;
 }
 
+static long btrfs_ioctl_alloc_chunk(struct file *file, void __user *arg)
+{
+       struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
+       struct btrfs_trans_handle *trans;
+       u64 flags;
+       int ret;
+
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+
+       if (copy_from_user(&flags, arg, sizeof(flags)))
+               return -EFAULT;
+
+       /* We can only specify one type at a time. */
+       if (flags != BTRFS_BLOCK_GROUP_DATA &&
+           flags != BTRFS_BLOCK_GROUP_METADATA &&
+           flags != BTRFS_BLOCK_GROUP_SYSTEM)
+               return -EINVAL;
+
+       trans = btrfs_start_transaction(root, 0);
+       if (IS_ERR(trans))
+               return PTR_ERR(trans);
+
+       ret = btrfs_chunk_alloc(trans, flags, CHUNK_ALLOC_FORCE);
+       btrfs_end_transaction(trans);
+       return ret < 0 ? ret : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
                cmd, unsigned long arg)
 {
@@ -5699,6 +5727,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                return btrfs_ioctl_get_subvol_rootref(file, argp);
        case BTRFS_IOC_INO_LOOKUP_USER:
                return btrfs_ioctl_ino_lookup_user(file, argp);
+       case BTRFS_IOC_ALLOC_CHUNK:
+               return btrfs_ioctl_alloc_chunk(file, argp);
        }
 
        return -ENOTTY;
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index c195896d478f..3a6474c34ad0 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -943,5 +943,6 @@ 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_ALLOC_CHUNK _IOR(BTRFS_IOCTL_MAGIC, 63, __u64)
 
 #endif /* _UAPI_LINUX_BTRFS_H */
-- 
2.21.0