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

[john . hubbard]

From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>

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 JÃrÃme's original patch:

* Changed a WARN_ON to a BUG_ON.

Signed-off-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: Jan Kara <jack@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Boaz Harrosh <boaz@xxxxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
---
 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