Re: [PATCH 07/12] vhost-scsi: convert put_page() to put_user_page*()

Michael S. Tsirkin
2019-07-24T08:08:10Z

On Tue, Jul 23, 2019 at 09:25:13PM -0700, john.hubbard@gmail.com wrote:
> From: Jérôme Glisse <jglisse@redhat.com>
>
> For pages that were retained via get_user_pages*(), release those pages
> via the new put_user_page*() routines, instead of via put_page().
>
> This is part a tree-wide conversion, as described in commit fc1d8e7cca2d
> ("mm: introduce put_user_page*(), placeholder versions").
>
> Changes from Jérôme's original patch:
>
> * Changed a WARN_ON to a BUG_ON.
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> Cc: virtualization@lists.linux-foundation.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-block@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Johannes Thumshirn <jthumshirn@suse.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Boaz Harrosh <boaz@plexistor.com>
> Cc: Miklos Szeredi <miklos@szeredi.hu>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
> drivers/vhost/scsi.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index a9caf1bc3c3e..282565ab5e3f 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -329,11 +329,11 @@ static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
>
> if (tv_cmd->tvc_sgl_count) {
> for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
> - put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> + put_user_page(sg_page(&tv_cmd->tvc_sgl[i]));
> }
> if (tv_cmd->tvc_prot_sgl_count) {
> for (i = 0; i < tv_cmd->tvc_prot_sgl_count; i++)
> - put_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
> + put_user_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
> }
>
> vhost_scsi_put_inflight(tv_cmd->inflight);
> @@ -630,6 +630,13 @@ vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,
> size_t offset;
> unsigned int npages = 0;
>
> + /*
> + * Here in all cases we should have an IOVEC which use GUP. If that is
> + * not the case then we will wrongly call put_user_page() and the page
> + * refcount will go wrong (this is in vhost_scsi_release_cmd())
> + */
> + WARN_ON(!iov_iter_get_pages_use_gup(iter));
> +
> bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
> VHOST_SCSI_PREALLOC_UPAGES, &offset);
> /* No pages were pinned */
> @@ -681,7 +688,7 @@ vhost_scsi_iov_to_sgl(struct vhost_scsi_cmd *cmd, bool write,
> while (p < sg) {
> struct page *page = sg_page(p++);
> if (page)
> - put_page(page);
> + put_user_page(page);
> }
> return ret;
> }
> --
> 2.22.0