Btrfs: fix ioctl arg size (userland incompatible change!)

The structure used to send device in btrfs ioctl calls was not
properly aligned, and so 32 bit ioctls would not work properly on
64 bit kernels.

We could fix this with compat ioctls, but we're just one byte away
and it doesn't make sense at this stage to carry about the compat ioctls
forever at this stage in the project.

This patch brings the ioctl arg up to an evenly aligned 4k.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index b4c101d9322c..92c9b543deff 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -582,7 +582,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 {
         struct btrfs_ioctl_vol_args *vol;
         struct btrfs_fs_devices *fs_devices;
-        int ret = 0;
+        int ret = -ENOTTY;
         int len;
 
         if (!capable(CAP_SYS_ADMIN))
@@ -594,6 +594,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
                 goto out;
         }
         len = strnlen(vol->name, BTRFS_PATH_NAME_MAX);
+
         switch (cmd) {
         case BTRFS_IOC_SCAN_DEV:
                 ret = btrfs_scan_one_device(vol->name, FMODE_READ,