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 <h...@lst.de>
Reviewed-by: Jan Kara <j...@suse.cz>
---
 fs/aio.c           |  6 ------
 fs/btrfs/file.c    |  6 +++++-
 fs/ext4/file.c     |  6 +++---
 fs/xfs/xfs_file.c  | 11 +++++++++--
 include/linux/fs.h |  6 +++---
 5 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index dcad3a66748c..d93daa076726 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1593,12 +1593,6 @@ static int io_submit_one(struct kioctx *ctx, struct iocb 
__user *user_iocb,
                goto out_put_req;
        }
 
-       if ((req->common.ki_flags & IOCB_NOWAIT) &&
-                       !(req->common.ki_flags & IOCB_DIRECT)) {
-               ret = -EOPNOTSUPP;
-               goto out_put_req;
-       }
-
        ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
        if (unlikely(ret)) {
                pr_debug("EFAULT: aio_key\n");
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 9e75d8a39aac..e62dd55b4079 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1886,6 +1886,10 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
        loff_t oldsize;
        int clean_page = 0;
 
+       if (!(iocb->ki_flags & IOCB_DIRECT) &&
+           (iocb->ki_flags & IOCB_NOWAIT))
+               return -EOPNOTSUPP;
+
        if (!inode_trylock(inode)) {
                if (iocb->ki_flags & IOCB_NOWAIT)
                        return -EAGAIN;
@@ -3105,7 +3109,7 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t 
offset, int whence)
 
 static int btrfs_file_open(struct inode *inode, struct file *filp)
 {
-       filp->f_mode |= FMODE_AIO_NOWAIT;
+       filp->f_mode |= FMODE_NOWAIT;
        return generic_file_open(inode, filp);
 }
 
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);
 }
 
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index c4893e226fd8..1a09104b3eb0 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -259,7 +259,11 @@ xfs_file_buffered_aio_read(
 
        trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos);
 
-       xfs_ilock(ip, XFS_IOLOCK_SHARED);
+       if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED)) {
+               if (iocb->ki_flags & IOCB_NOWAIT)
+                       return -EAGAIN;
+               xfs_ilock(ip, XFS_IOLOCK_SHARED);
+       }
        ret = generic_file_read_iter(iocb, to);
        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
 
@@ -636,6 +640,9 @@ xfs_file_buffered_aio_write(
        int                     enospc = 0;
        int                     iolock;
 
+       if (iocb->ki_flags & IOCB_NOWAIT)
+               return -EOPNOTSUPP;
+
 write_retry:
        iolock = XFS_IOLOCK_EXCL;
        xfs_ilock(ip, iolock);
@@ -912,7 +919,7 @@ xfs_file_open(
                return -EFBIG;
        if (XFS_FORCED_SHUTDOWN(XFS_M(inode->i_sb)))
                return -EIO;
-       file->f_mode |= FMODE_AIO_NOWAIT;
+       file->f_mode |= FMODE_NOWAIT;
        return 0;
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6e1fd5d21248..ded258edc425 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;
        }
-- 
2.11.0

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