[patch 11/16] mm,hwpoison: unmap poisoned page before invalidation

[Andrew Morton <akpm@linux-foundation.org>]

From: Rik van Riel <riel@surriel.com>
Subject: mm,hwpoison: unmap poisoned page before invalidation

In some cases it appears the invalidation of a hwpoisoned page fails
because the page is still mapped in another process.  This can cause a
program to be continuously restarted and die when it page faults on the
page that was not invalidated.  Avoid that problem by unmapping the
hwpoisoned page when we find it.

Another issue is that sometimes we end up oopsing in finish_fault, if the
code tries to do something with the now-NULL vmf->page.  I did not hit
this error when submitting the previous patch because there are several
opportunities for alloc_set_pte to bail out before accessing vmf->page,
and that apparently happened on those systems, and most of the time on
other systems, too.

However, across several million systems that error does occur a handful of
times a day.  It can be avoided by returning VM_FAULT_NOPAGE which will
cause do_read_fault to return before calling finish_fault.

Link: https://lkml.kernel.org/r/20220325161428.5068d97e@imladris.surriel.com
Fixes: e53ac7374e64 ("mm: invalidate hwpoison page cache page in fault path")
Signed-off-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Tested-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/mm/memory.c~mmhwpoison-unmap-poisoned-page-before-invalidation
+++ a/mm/memory.c
@@ -3918,14 +3918,18 @@ static vm_fault_t __do_fault(struct vm_f
 		return ret;
 
 	if (unlikely(PageHWPoison(vmf->page))) {
+		struct page *page = vmf->page;
 		vm_fault_t poisonret = VM_FAULT_HWPOISON;
 		if (ret & VM_FAULT_LOCKED) {
+			if (page_mapped(page))
+				unmap_mapping_pages(page_mapping(page),
+						    page->index, 1, false);
 			/* Retry if a clean page was removed from the cache. */
-			if (invalidate_inode_page(vmf->page))
-				poisonret = 0;
-			unlock_page(vmf->page);
+			if (invalidate_inode_page(page))
+				poisonret = VM_FAULT_NOPAGE;
+			unlock_page(page);
 		}
-		put_page(vmf->page);
+		put_page(page);
 		vmf->page = NULL;
 		return poisonret;
 	}
_