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/include/linux/fs.h b/include/linux/fs.h
index cbfe127bccf8..94582c379dac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -146,8 +146,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 /* File was opened by fanotify and shouldn't generate fanotify events */
 #define FMODE_NONOTIFY          ((__force fmode_t)0x4000000)
 
-/* File is capable of returning -EAGAIN if AIO will block */
-#define FMODE_AIO_NOWAIT        ((__force fmode_t)0x8000000)
+/* File is capable of returning -EAGAIN if I/O will block */
+#define FMODE_NOWAIT    ((__force fmode_t)0x8000000)
 
 /*
  * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector
@@ -3149,7 +3149,7 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, int flags)
                 return -EOPNOTSUPP;
 
         if (flags & RWF_NOWAIT) {
-                if (!(ki->ki_filp->f_mode & FMODE_AIO_NOWAIT))
+                if (!(ki->ki_filp->f_mode & FMODE_NOWAIT))
                         return -EOPNOTSUPP;
                 ki->ki_flags |= IOCB_NOWAIT;
         }