ioprio: allow sys_ioprio_set() value of 0 to reset ioprio setting

Normally io priorities follow the CPU nice, unless a specific scheduling
class has been set. Once that is set, there's no way to reset the
behaviour to 'none' so that it follows CPU nice again.

Currently passing in 0 as the ioprio class/value will return -1/EINVAL,
change that to allow resetting of a set scheduling class.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/ioprio.c b/fs/ioprio.c
index d6ff77e8e7e..e4e01bc7f33 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -78,6 +78,10 @@ asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
                         if (!capable(CAP_SYS_ADMIN))
                                 return -EPERM;
                         break;
+                case IOPRIO_CLASS_NONE:
+                        if (data)
+                                return -EINVAL;
+                        break;
                 default:
                         return -EINVAL;
         }