vfs: add the RWF_HIPRI flag for preadv2/pwritev2

This adds a flag that tells the file system that this is a high priority
request for which it's worth to poll the hardware.  The flag is purely
advisory and can be ignored if not supported.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stephen Bates <stephen.bates@pmcs.com>
Tested-by: Stephen Bates <stephen.bates@pmcs.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index e9c9e2a667ce..07c53db04ec1 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -697,10 +697,12 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
         struct kiocb kiocb;
         ssize_t ret;
 
-        if (flags)
+        if (flags & ~RWF_HIPRI)
                 return -EOPNOTSUPP;
 
         init_sync_kiocb(&kiocb, filp);
+        if (flags & RWF_HIPRI)
+                kiocb.ki_flags |= IOCB_HIPRI;
         kiocb.ki_pos = *ppos;
 
         ret = fn(&kiocb, iter);
@@ -715,7 +717,7 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
 {
         ssize_t ret = 0;
 
-        if (flags)
+        if (flags & ~RWF_HIPRI)
                 return -EOPNOTSUPP;
 
         while (iov_iter_count(iter)) {