[PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16

[adam . manzanares]

From: Adam Manzanares <adam.manzana...@wdc.com>

In order to avoid kiocb bloat for per command iopriority support, rw_hint
is converted from enum to a u16. Added a guard around ki_hint assigment.

Signed-off-by: Adam Manzanares <adam.manzana...@wdc.com>
---
 include/linux/fs.h | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 760d8da1b6c7..7a90ce387e00 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -284,6 +284,8 @@ enum rw_hint {
        WRITE_LIFE_EXTREME      = RWH_WRITE_LIFE_EXTREME,
 };
 
+#define MAX_KI_HINT            ((1 << 16) - 1) /* ki_hint type is u16 */
+
 #define IOCB_EVENTFD           (1 << 0)
 #define IOCB_APPEND            (1 << 1)
 #define IOCB_DIRECT            (1 << 2)
@@ -299,7 +301,7 @@ struct kiocb {
        void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
        void                    *private;
        int                     ki_flags;
-       enum rw_hint            ki_hint;
+       u16                     ki_hint;
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1927,12 +1929,21 @@ static inline enum rw_hint file_write_hint(struct file 
*file)
 
 static inline int iocb_flags(struct file *file);
 
+/* ki_hint changed from enum to u16, make sure rw_hint fits into u16 */
+static inline u16 ki_hint_valid(enum rw_hint hint)
+{
+       if (hint > MAX_KI_HINT)
+               return 0;
+
+       return hint;
+}
+
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
        *kiocb = (struct kiocb) {
                .ki_filp = filp,
                .ki_flags = iocb_flags(filp),
-               .ki_hint = file_write_hint(filp),
+               .ki_hint = ki_hint_valid(file_write_hint(filp)),
        };
 }
 
-- 
2.15.1