On Thu, Jan 26, 2023 at 04:39:02PM +0100, Claudio Imbrenda wrote:
> I can tell you that the original goal of that function is to make sure
> that there are no extra references. in particular, we want to prevent
> I/O of any kind to be ongoing while the page becomes secure. (the I/O
> will fail and, depending on which device it was, the whole system might
> end up in a rather unhappy state)
Sure, but if there is concurrent IO you just try again right? It
doesn't wait for refs to drop for instance.
So make the lock_page work the same way:
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
index 9f18a4af9c1319..847ee50b8672c6 100644
--- a/arch/s390/kernel/uv.c
+++ b/arch/s390/kernel/uv.c
@@ -193,20 +193,11 @@ static int expected_page_refs(struct page *page)
}
static int make_secure_pte(pte_t *ptep, unsigned long addr,
- struct page *exp_page, struct uv_cb_header *uvcb)
+ struct page *page, struct uv_cb_header *uvcb)
{
pte_t entry = READ_ONCE(*ptep);
- struct page *page;
int expected, cc = 0;
- if (!pte_present(entry))
- return -ENXIO;
- if (pte_val(entry) & _PAGE_INVALID)
- return -ENXIO;
-
- page = pte_page(entry);
- if (page != exp_page)
- return -ENXIO;
if (PageWriteback(page))
return -EAGAIN;
expected = expected_page_refs(page);
@@ -304,17 +295,25 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)
goto out;
rc = -ENXIO;
- page = follow_page(vma, uaddr, FOLL_WRITE);
- if (IS_ERR_OR_NULL(page))
- goto out;
-
- lock_page(page);
ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);
+
+ if (!pte_present(entry))
+ goto out_unlock_pte;
+ if (pte_val(entry) & _PAGE_INVALID)
+ goto out_unlock_pte;
+ page = pte_page(entry);
+
+ if (!trylock_page(page)) {
+ rc = -EAGAIN;
+ goto out_unlock_pte;
+ }
+
if (should_export_before_import(uvcb, gmap->mm))
uv_convert_from_secure(page_to_phys(page));
rc = make_secure_pte(ptep, uaddr, page, uvcb);
- pte_unmap_unlock(ptep, ptelock);
unlock_page(page);
+out_unlock_pte:
+ pte_unmap_unlock(ptep, ptelock);
out:
mmap_read_unlock(gmap->mm);
