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>

1 files changed, 16 insertions, 0 deletions

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);