fs: Convert kiocb rw_hint from enum to u16

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.manzanares@wdc.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 12 insertions, 3 deletions

diff --git a/fs/aio.c b/fs/aio.c
index b850e92ee0d5..33299ece7540 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1434,7 +1434,7 @@ 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 4b6045ebb2f2..b432fc3feb93 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)
@@ -1929,12 +1929,21 @@ 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)),
         };
 }