[PATCH][v2] btrfs: add an ioctl to force chunk allocation

[Josef Bacik <josef@toxicpanda.com>]

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 <josef@toxicpanda.com>
---
v1->v2:
- I noticed last week when backporting this that btrfs_chunk_alloc doesn't
  figure out the rest of the flags needed for the type.  Use
  btrfs_force_chunk_alloc instead so that we get the raid settings for the alloc
  type we're using.

 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..891bf198d46a 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_force_chunk_alloc(trans, flags);
+	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