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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: Jennifer Herbert <jennifer.herbert@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Jennifer Herbert 2015-01-05 15:07:46 +00:00 committed by David Vrabel
parent 1401c00e59
commit 745282256c
1 changed files with 31 additions and 5 deletions
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36
drivers/xen/gntdev.c
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@ -309,9 +309,30 @@ static int map_grant_pages(struct grant_map *map)
return err; 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) static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
{ {
int i, err = 0; 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) { if (map->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
int pgno = (map->notify.addr >> PAGE_SHIFT); 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, unmap_data.unmap_ops = map->unmap_ops + offset;
use_ptemod ? map->kunmap_ops + offset : NULL, map->pages + offset, unmap_data.kunmap_ops = use_ptemod ? map->kunmap_ops + offset : NULL;
pages); unmap_data.pages = map->pages + offset;
if (err) unmap_data.count = pages;
return err;
gnttab_unmap_refs_async(&unmap_data);
wait_for_completion(&data.completion);
if (data.result)
return data.result;
for (i = 0; i < pages; i++) { for (i = 0; i < pages; i++) {
if (map->unmap_ops[offset+i].status) if (map->unmap_ops[offset+i].status)