linux-kernel - [PATCH v3 2/3] fs: Convert kiocb rw

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Message-Id: <20180508174202.2537-3-adam.manzanares@wdc.com>
Date:   Tue,  8 May 2018 10:42:01 -0700
From:   adam.manzanares@....com
To:     viro@...iv.linux.org.uk, bcrl@...ck.org
Cc:     linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
        linux-api@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Adam Manzanares <adam.manzanares@....com>
Subject: [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16

From: Adam Manzanares <adam.manzanares@....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.manzanares@....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