fs: Add aio iopriority support

This is the per-I/O equivalent of the ioprio_set system call.

When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.

This patch depends on block: add ioprio_check_cap function.

Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Al Viro <[email protected]>
(cherry picked from commit d9a08a9e616beeccdbd0e7262b7225ffdfa49e92)
Signed-off-by: alk3pInjection <[email protected]>

Author: nmtadam

drivers/block/loop.c

@@ -76,6 +76,8 @@
 #include <linux/miscdevice.h>
 #include <linux/falloc.h>
 #include <linux/uio.h>
+#include <linux/ioprio.h>
+
 #include "loop.h"
 
 #include <linux/uaccess.h>
@@ -539,6 +541,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 	cmd->iocb.ki_filp = file;
 	cmd->iocb.ki_complete = lo_rw_aio_complete;
 	cmd->iocb.ki_flags = IOCB_DIRECT;
+	cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
 
 	if (rw == WRITE)
 		ret = call_write_iter(file, &cmd->iocb, &iter);

fs/aio.c

@@ -1471,6 +1471,22 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
 	if (iocb->aio_flags & IOCB_FLAG_RESFD)
 		req->ki_flags |= IOCB_EVENTFD;
 	req->ki_hint = ki_hint_validate(file_write_hint(req->ki_filp));
+	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
+		/*
+		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
+		 * aio_reqprio is interpreted as an I/O scheduling
+		 * class and priority.
+		 */
+		ret = ioprio_check_cap(iocb->aio_reqprio);
+		if (ret) {
+			pr_debug("aio ioprio check cap error\n");
+			return -EINVAL;
+		}
+
+		req->ki_ioprio = iocb->aio_reqprio;
+	} else
+		req->ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+
 	ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
 	if (unlikely(ret))
 		fput(req->ki_filp);

include/linux/fs.h

@@ -35,6 +35,7 @@
 #include <linux/delayed_call.h>
 #include <linux/uuid.h>
 #include <linux/errseq.h>
+#include <linux/ioprio.h>
 
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
@@ -306,6 +307,7 @@ struct kiocb {
 	void			*private;
 	int			ki_flags;
 	u16			ki_hint;
+	u16			ki_ioprio; /* See linux/ioprio.h */
 } __randomize_layout;
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1982,6 +1984,7 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 		.ki_filp = filp,
 		.ki_flags = iocb_flags(filp),
 		.ki_hint = ki_hint_validate(file_write_hint(filp)),
+		.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0),
 	};
 }
 

include/uapi/linux/aio_abi.h

@@ -54,6 +54,7 @@ enum {
  *                   is valid.
  */
 #define IOCB_FLAG_RESFD		(1 << 0)
+#define IOCB_FLAG_IOPRIO	(1 << 1)
 
 /* read() from /dev/aio returns these structures. */
 struct io_event {