[PATCH v2 13/13] block: enable async buffered writes for block devices.

[Stefan Roesch <shr@fb.com>]

This introduces the flag FMODE_BUF_WASYNC. If devices support async
buffered writes, this flag can be set. It also enables async buffered
writes for block devices.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 block/fops.c       | 5 +----
 fs/read_write.c    | 3 ++-
 include/linux/fs.h | 3 +++
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 4f59e0f5bf30..75b36f8b5e71 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -489,7 +489,7 @@ static int blkdev_open(struct inode *inode, struct file *filp)
 	 * during an unstable branch.
 	 */
 	filp->f_flags |= O_LARGEFILE;
-	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC;
+	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC | FMODE_BUF_WASYNC;
 
 	if (filp->f_flags & O_NDELAY)
 		filp->f_mode |= FMODE_NDELAY;
@@ -544,9 +544,6 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_pos >= size)
 		return -ENOSPC;
 
-	if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
-		return -EOPNOTSUPP;
-
 	size -= iocb->ki_pos;
 	if (iov_iter_count(from) > size) {
 		shorted = iov_iter_count(from) - size;
diff --git a/fs/read_write.c b/fs/read_write.c
index 0074afa7ecb3..58233844a9d8 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1641,7 +1641,8 @@ ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_flags & IOCB_APPEND)
 		iocb->ki_pos = i_size_read(inode);
 
-	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
+	if ((iocb->ki_flags & IOCB_NOWAIT) &&
+		(!(iocb->ki_flags & IOCB_DIRECT) && !(file->f_mode & FMODE_BUF_WASYNC)))
 		return -EINVAL;
 
 	count = iov_iter_count(from);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b7dd5bd701c0..a526de71b932 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -176,6 +176,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
 /* File supports async buffered reads */
 #define FMODE_BUF_RASYNC	((__force fmode_t)0x40000000)
 
+/* File supports async nowait buffered writes */
+#define FMODE_BUF_WASYNC	((__force fmode_t)0x80000000)
+
 /*
  * Attribute flags.  These should be or-ed together to figure out what
  * has been changed!
-- 
2.30.2