From 096c9482cea201aef3fc7f532fcc209f51cbdefd Mon Sep 17 00:00:00 2001
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Date: Tue, 4 May 2021 18:38:46 -0700
Subject: [PATCH] mm/gup: return an error on migration failure

[ Upstream commit f0f4463837da17a89d965dcbe4e411629dbcf308 ]

When migration failure occurs, we still pin pages, which means that we
may pin CMA movable pages which should never be the case.

Instead return an error without pinning pages when migration failure
happens.

No need to retry migrating, because migrate_pages() already retries 10
times.

Link: https://lkml.kernel.org/r/20210215161349.246722-4-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/gup.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index e10807c4c46b7..0fa8d88eb7ba6 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1563,7 +1563,6 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 {
 	unsigned long i;
 	bool drain_allow = true;
-	bool migrate_allow = true;
 	LIST_HEAD(cma_page_list);
 	long ret = nr_pages;
 	struct page *prev_head, *head;
@@ -1614,17 +1613,15 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 			for (i = 0; i < nr_pages; i++)
 				put_page(pages[i]);
 
-		if (migrate_pages(&cma_page_list, alloc_migration_target, NULL,
-			(unsigned long)&mtc, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
-			/*
-			 * some of the pages failed migration. Do get_user_pages
-			 * without migration.
-			 */
-			migrate_allow = false;
-
+		ret = migrate_pages(&cma_page_list, alloc_migration_target,
+				    NULL, (unsigned long)&mtc, MIGRATE_SYNC,
+				    MR_CONTIG_RANGE);
+		if (ret) {
 			if (!list_empty(&cma_page_list))
 				putback_movable_pages(&cma_page_list);
+			return ret > 0 ? -ENOMEM : ret;
 		}
+
 		/*
 		 * We did migrate all the pages, Try to get the page references
 		 * again migrating any new CMA pages which we failed to isolate
@@ -1634,7 +1631,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 						   pages, vmas, NULL,
 						   gup_flags);
 
-		if ((ret > 0) && migrate_allow) {
+		if (ret > 0) {
 			nr_pages = ret;
 			drain_allow = true;
 			goto check_again;