fs: add a FMODE_BUF_WASYNC flags for f_mode

This introduces the flag FMODE_BUF_WASYNC. If devices support async
buffered writes, this flag can be set. It also modifies the check in
generic_write_checks to take async buffered writes into consideration.

Signed-off-by: Stefan Roesch <shr@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220623175157.1715274-8-shr@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/read_write.c b/fs/read_write.c
index e0777ee..319d888 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1660,7 +1660,9 @@ int generic_write_checks_count(struct kiocb *iocb, loff_t *count)
        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;
 
        return generic_write_check_limits(iocb->ki_filp, iocb->ki_pos, count);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9ad5e35..bc84847 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -180,6 +180,9 @@ 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!