btrfs: use struct qstr instead of name and namelen pairs

Many functions throughout btrfs take name buffer and name length
arguments. Most of these functions at the highest level are usually
called with these arguments extracted from a supplied dentry's name.
But the entire name can be passed instead, making each function a little
more elegant.

Each function whose arguments are currently the name and length
extracted from a dentry is herein converted to instead take a pointer to
the name in the dentry. The couple of calls to these calls without a
struct dentry are converted to create an appropriate qstr to pass in.
Additionally, every function which is only called with a name/len
extracted directly from a qstr is also converted.

This change has positive effect on stack consumption, frame of many
functions is reduced but this will be used in the future for fscrypt
related structures.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e33be4032fff..fde55d0f61b4 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -951,6 +951,7 @@ static noinline int btrfs_mksubvol(const struct path *parent,
 	struct inode *dir = d_inode(parent->dentry);
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct dentry *dentry;
+	struct qstr name_str = QSTR_INIT(name, namelen);
 	int error;
 
 	error = down_write_killable_nested(&dir->i_rwsem, I_MUTEX_PARENT);
@@ -971,8 +972,7 @@ static noinline int btrfs_mksubvol(const struct path *parent,
 	 * check for them now when we can safely fail
 	 */
 	error = btrfs_check_dir_item_collision(BTRFS_I(dir)->root,
-					       dir->i_ino, name,
-					       namelen);
+					       dir->i_ino, &name_str);
 	if (error)
 		goto out_dput;
 
@@ -3779,6 +3779,7 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 	struct btrfs_trans_handle *trans;
 	struct btrfs_path *path = NULL;
 	struct btrfs_disk_key disk_key;
+	struct qstr name = QSTR_INIT("default", 7);
 	u64 objectid = 0;
 	u64 dir_id;
 	int ret;
@@ -3822,7 +3823,7 @@ static long btrfs_ioctl_default_subvol(struct file *file, void __user *argp)
 
 	dir_id = btrfs_super_root_dir(fs_info->super_copy);
 	di = btrfs_lookup_dir_item(trans, fs_info->tree_root, path,
-				   dir_id, "default", 7, 1);
+				   dir_id, &name, 1);
 	if (IS_ERR_OR_NULL(di)) {
 		btrfs_release_path(path);
 		btrfs_end_transaction(trans);