Commit e70344c05995 ("block: fix default IO priority handling")
introduced an inconsistency in get_current_ioprio() that tasks without
IO context return IOPRIO_DEFAULT priority while tasks with freshly
allocated IO context will return 0 (IOPRIO_CLASS_NONE/0) IO priority.
Tasks without IO context used to be rare before 5a9d041ba2f6 ("block:
move io_context creation into where it's needed") but after this commit
they became common because now only BFQ IO scheduler setups task's IO
context. Similar inconsistency is there for get_task_ioprio() so this
inconsistency is now exposed to userspace and userspace will see
different IO priority for tasks operating on devices with BFQ compared
to devices without BFQ. Furthemore the changes done by commit
e70344c05995 change the behavior when no IO priority is set for BFQ IO
scheduler which is also documented in ioprio_set(2) manpage - namely
that tasks without set IO priority will use IO priority based on their
nice value.
So make sure we default to IOPRIO_CLASS_NONE as used to be the case
before commit e70344c05995. Also cleanup alloc_io_context() to
explicitely set this IO priority for the allocated IO context.
Fixes: e70344c05995 ("block: fix default IO priority handling")
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
block/blk-ioc.c | 2 ++
include/linux/ioprio.h | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index df9cfe4ca532..63fc02042408 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -247,6 +247,8 @@ static struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
INIT_HLIST_HEAD(&ioc->icq_list);
INIT_WORK(&ioc->release_work, ioc_release_fn);
#endif
+ ioc->ioprio = IOPRIO_DEFAULT;
+
return ioc;
}
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 774bb90ad668..d9dc78a15301 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -11,7 +11,7 @@
/*
* Default IO priority.
*/
-#define IOPRIO_DEFAULT IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_BE_NORM)
+#define IOPRIO_DEFAULT IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0)
/*
* Check that a priority value has a valid class.
--
2.35.3
