fs/block: Check for IOCB_DIRECT in generic_atomic_write_valid()

Currently FMODE_CAN_ATOMIC_WRITE is set if the bdev can atomic write and
the file is open for direct IO. This does not work if the file is not
opened for direct IO, yet fcntl(O_DIRECT) is used on the fd later.

Change to check for direct IO on a per-IO basis in
generic_atomic_write_valid(). Since we want to report -EOPNOTSUPP for
non-direct IO for an atomic write, change to return an error code.

Relocate the block fops atomic write checks to the common write path, as to
catch non-direct IO.

Fixes: c34fc6f26ab8 ("fs: Initial atomic write support")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20241019125113.369994-3-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index 2c3263530828..befec0b5c537 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1830,18 +1830,21 @@ int generic_file_rw_checks(struct file *file_in, struct file *file_out)
 	return 0;
 }
 
-bool generic_atomic_write_valid(struct kiocb *iocb, struct iov_iter *iter)
+int generic_atomic_write_valid(struct kiocb *iocb, struct iov_iter *iter)
 {
 	size_t len = iov_iter_count(iter);
 
 	if (!iter_is_ubuf(iter))
-		return false;
+		return -EINVAL;
 
 	if (!is_power_of_2(len))
-		return false;
+		return -EINVAL;
 
 	if (!IS_ALIGNED(iocb->ki_pos, len))
-		return false;
+		return -EINVAL;
 
-	return true;
+	if (!(iocb->ki_flags & IOCB_DIRECT))
+		return -EOPNOTSUPP;
+
+	return 0;
 }