[PATCH v7 2/5] 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 assignment.

Signed-off-by: Adam Manzanares <adam.manzana...@wdc.com>
---
 fs/aio.c           |  2 +-
 include/linux/fs.h | 13 +++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 755d3f57bcc8..87d8939bb1e4 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1450,7 +1450,7 @@ static int aio_prep_rw(struct kiocb *req, struct iocb 
*iocb)
        req->ki_flags = iocb_flags(req->ki_filp);
        if (iocb->aio_flags & IOCB_FLAG_RESFD)
                req->ki_flags |= IOCB_EVENTFD;
-       req->ki_hint = file_write_hint(req->ki_filp);
+       req->ki_hint = ki_hint_validate(file_write_hint(req->ki_filp));
        ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
        if (unlikely(ret))
                fput(req->ki_filp);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7f07977bdfd7..9b76ee73af14 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -299,7 +299,7 @@ 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 +1927,21 @@ static inline enum rw_hint file_write_hint(struct file 
*file)
 
 static inline int iocb_flags(struct file *file);
 
+static inline u16 ki_hint_validate(enum rw_hint hint)
+{
+       typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
+
+       if (hint <= max_hint)
+               return hint;
+       return 0;
+}
+
 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_validate(file_write_hint(filp)),
        };
 }
 
-- 
2.15.1