An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
in the block layer. E.g. ioprio_check_cap() takes an int as argument.
With such implicit int casting function calls, the upper 16-bits of the
int argument may be left uninitialized by the compiler, resulting in
invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
and in an error return for functions such as ioprio_check_cap().
Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
defines the 3-bits mask for the priority class.
While at it, cleanup the following:
* Apply the mask IOPRIO_PRIO_MASK to the data argument of the
IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
* Remove unnecessary parenthesis around fixed values in the macro
definitions in include/uapi/linux/ioprio.h.
* Update the outdated mention of CFQ in the comment describing priority
classes and instead mention BFQ and mq-deadline.
* Change the argument name of the IOPRIO_PRIO_CLASS() and
IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
that an IO priority value should be passed rather than a mask.
* Change the ioprio_valid() macro into an inline function, adding a
check on the maximum value of the class of a priority value as
defined by the IOPRIO_CLASS_MAX enum value. Move this function to
the kernel side in include/linux/ioprio.h.
* Remove the unnecessary "else" after the return statements in
task_nice_ioclass().
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
---
include/linux/ioprio.h | 15 ++++++++++++---
include/uapi/linux/ioprio.h | 19 +++++++++++--------
2 files changed, 23 insertions(+), 11 deletions(-)
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index ef9ad4fb245f..9b3a6d8172b4 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -8,6 +8,16 @@
#include <uapi/linux/ioprio.h>
+/*
+ * Check that a priority value has a valid class.
+ */
+static inline bool ioprio_valid(unsigned short ioprio)
+{
+ unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
+
+ return class > IOPRIO_CLASS_NONE && class < IOPRIO_CLASS_MAX;
+}
+
/*
* if process has set io priority explicitly, use that. if not, convert
* the cpu scheduler nice value to an io priority
@@ -25,10 +35,9 @@ static inline int task_nice_ioclass(struct task_struct *task)
{
if (task->policy == SCHED_IDLE)
return IOPRIO_CLASS_IDLE;
- else if (task_is_realtime(task))
+ if (task_is_realtime(task))
return IOPRIO_CLASS_RT;
- else
- return IOPRIO_CLASS_BE;
+ return IOPRIO_CLASS_BE;
}
/*
diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
index 77b17e08b0da..abc40965aa96 100644
--- a/include/uapi/linux/ioprio.h
+++ b/include/uapi/linux/ioprio.h
@@ -5,12 +5,15 @@
/*
* Gives us 8 prio classes with 13-bits of data for each class
*/
-#define IOPRIO_CLASS_SHIFT (13)
+#define IOPRIO_CLASS_SHIFT 13
+#define IOPRIO_CLASS_MASK 0x07
#define IOPRIO_PRIO_MASK ((1UL << IOPRIO_CLASS_SHIFT) - 1)
-#define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
-#define IOPRIO_PRIO_DATA(mask) ((mask) & IOPRIO_PRIO_MASK)
-#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
+#define IOPRIO_PRIO_CLASS(ioprio) \
+ (((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
+#define IOPRIO_PRIO_DATA(ioprio) ((ioprio) & IOPRIO_PRIO_MASK)
+#define IOPRIO_PRIO_VALUE(class, data) \
+ (((class) << IOPRIO_CLASS_SHIFT) | ((data) & IOPRIO_PRIO_MASK))
/*
* These are the io priority groups as implemented by CFQ. RT is the realtime
@@ -23,14 +26,14 @@ enum {
IOPRIO_CLASS_RT,
IOPRIO_CLASS_BE,
IOPRIO_CLASS_IDLE,
-};
-#define ioprio_valid(mask) (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
+ IOPRIO_CLASS_MAX,
+};
/*
* 8 best effort priority levels are supported
*/
-#define IOPRIO_BE_NR (8)
+#define IOPRIO_BE_NR 8
enum {
IOPRIO_WHO_PROCESS = 1,
@@ -41,6 +44,6 @@ enum {
/*
* Fallback BE priority
*/
-#define IOPRIO_NORM (4)
+#define IOPRIO_NORM 4
#endif /* _UAPI_LINUX_IOPRIO_H */
--
2.31.1
