Re: [PATCH 2/2] dax: assert that i_rwsem is held exclusive for writes

Jan Kara
2017-01-11T09:02:50Z

On Tue 10-01-17 16:48:08, Christoph Hellwig wrote:
> Make sure all callers follow the same locking protocol, given that DAX
> transparantly replaced the normal buffered I/O path.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Probably also for Ted since it depends on the ext4 fix...

Honza
> ---
> fs/dax.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 5c74f60..04734da 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1061,8 +1061,12 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
> loff_t pos = iocb->ki_pos, ret = 0, done = 0;
> unsigned flags = 0;
>
> - if (iov_iter_rw(iter) == WRITE)
> + if (iov_iter_rw(iter) == WRITE) {
> + lockdep_assert_held_exclusive(&inode->i_rwsem);
> flags |= IOMAP_WRITE;
> + } else {
> + lockdep_assert_held(&inode->i_rwsem);
> + }
>
> while (iov_iter_count(iter)) {
> ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
> --
> 2.1.4
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR