xen/grant-table: Support mappings required by blkback
Add support for mappings without GNTMAP_contains_pte. This was not
supported because the unmap operation assumed that this flag was being
used; adding a parameter to the unmap operation to allow the PTE
clearing to be disabled is sufficient to make unmap capable of
supporting either mapping type.
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
[v1: Fix cleanpatch warnings]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index a3d0e1e..1cd94da 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -761,24 +761,10 @@
(map_ops[i].host_addr & ~PAGE_MASK));
mfn = pte_mfn(*pte);
} else {
- /* If you really wanted to do this:
- * mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
- *
- * The reason we do not implement it is b/c on the
- * unmap path (gnttab_unmap_refs) we have no means of
- * checking whether the page is !GNTMAP_contains_pte.
- *
- * That is without some extra data-structure to carry
- * the struct page, bool clear_pte, and list_head next
- * tuples and deal with allocation/delallocation, etc.
- *
- * The users of this API set the GNTMAP_contains_pte
- * flag so lets just return not supported until it
- * becomes neccessary to implement.
- */
- return -EOPNOTSUPP;
+ mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
}
- ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
+ ret = m2p_add_override(mfn, pages[i], kmap_ops ?
+ &kmap_ops[i] : NULL);
if (ret)
return ret;
}
@@ -788,7 +774,7 @@
EXPORT_SYMBOL_GPL(gnttab_map_refs);
int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
- struct page **pages, unsigned int count)
+ struct page **pages, unsigned int count, bool clear_pte)
{
int i, ret;
@@ -800,7 +786,7 @@
return ret;
for (i = 0; i < count; i++) {
- ret = m2p_remove_override(pages[i], true /* clear the PTE */);
+ ret = m2p_remove_override(pages[i], clear_pte);
if (ret)
return ret;
}