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 <adam.manzanares@wdc.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 23 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5d4e31655d96..dd98dfd97f5e 100644
--- a/drivers/block/loop.c
+++ b/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>
@@ -559,6 +561,7 @@ 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 (cmd->css)
                 kthread_associate_blkcg(cmd->css);
 
diff --git a/fs/aio.c b/fs/aio.c
index 33299ece7540..9527ededa669 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1435,6 +1435,22 @@ 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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b432fc3feb93..eef9334b26d1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -36,6 +36,7 @@
 #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>
@@ -300,6 +301,7 @@ 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)
@@ -1944,6 +1946,7 @@ 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),
         };
 }
 
diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index ed0185945bb2..75846164290e 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -53,6 +53,7 @@ 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 {