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Commit 74528225 authored by Jennifer Herbert's avatar Jennifer Herbert Committed by David Vrabel
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xen/gntdev: safely unmap grants in case they are still in use 



Use gnttab_unmap_refs_async() to wait until the mapped pages are no
longer in use before unmapping them.

This allows userspace programs to safely use Direct I/O and AIO to a
network filesystem which may retain refs to pages in queued skbs after
the filesystem I/O has completed.

Signed-off-by: default avatarJennifer Herbert <jennifer.herbert@citrix.com>
Reviewed-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
parent 1401c00e

drivers/xen/gntdev.c

+31 −5
Original line number Diff line number Diff line
@@ -309,9 +309,30 @@ static int map_grant_pages(struct grant_map *map) 
	return err;

}



struct unmap_grant_pages_callback_data

{

	struct completion completion;

	int result;

};



static void unmap_grant_callback(int result,

				 struct gntab_unmap_queue_data *data)

{

	struct unmap_grant_pages_callback_data* d = data->data;



	d->result = result;

	complete(&d->completion);

}



static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)

{

	int i, err = 0;

	struct gntab_unmap_queue_data unmap_data;

	struct unmap_grant_pages_callback_data data;



	init_completion(&data.completion);

	unmap_data.data = &data;

	unmap_data.done= &unmap_grant_callback;



	if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {

		int pgno = (map->notify.addr >> PAGE_SHIFT);
@@ -323,11 +344,16 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages) 
		}

	}



	err = gnttab_unmap_refs(map->unmap_ops + offset,

			use_ptemod ? map->kunmap_ops + offset : NULL, map->pages + offset,

			pages);

	if (err)

		return err;

	unmap_data.unmap_ops = map->unmap_ops + offset;

	unmap_data.kunmap_ops = use_ptemod ? map->kunmap_ops + offset : NULL;

	unmap_data.pages = map->pages + offset;

	unmap_data.count = pages;



	gnttab_unmap_refs_async(&unmap_data);



	wait_for_completion(&data.completion);

	if (data.result)

		return data.result;



	for (i = 0; i < pages; i++) {

		if (map->unmap_ops[offset+i].status)