fs: support RWF_NOWAIT for buffered reads

This is based on the old idea and code from Milosz Tanski.  With the aio
nowait code it becomes mostly trivial now.  Buffered writes continue to
return -EOPNOTSUPP if RWF_NOWAIT is passed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 0d7cf0cc9b87..f83521337b8f 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -223,6 +223,8 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         if (IS_DAX(inode))
                 return ext4_dax_write_iter(iocb, from);
 #endif
+        if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
+                return -EOPNOTSUPP;
 
         if (!inode_trylock(inode)) {
                 if (iocb->ki_flags & IOCB_NOWAIT)
@@ -448,9 +450,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
                         return ret;
         }
 
-        /* Set the flags to support nowait AIO */
-        filp->f_mode |= FMODE_AIO_NOWAIT;
-
+        filp->f_mode |= FMODE_NOWAIT;
         return dquot_file_open(inode, filp);
 }