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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Pavel Tatashin <pasha.tatashin@soleen.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Ira Weiny <ira.weiny@intel.com>,
        James Morris <jmorris@namei.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Oscar Salvador <osalvador@suse.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Sasha Levin <sashal@kernel.org>,
        "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Tyler Hicks <tyhicks@linux.microsoft.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 5.10 172/289] mm/gup: check for isolation errors
Date:   Mon, 17 May 2021 16:01:37 +0200
Message-Id: <20210517140310.911473206@linuxfoundation.org>
In-Reply-To: <20210517140305.140529752@linuxfoundation.org>
References: <20210517140305.140529752@linuxfoundation.org>
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From: Pavel Tatashin <pasha.tatashin@soleen.com>

[ Upstream commit 6e7f34ebb8d25d71ce7f4580ba3cbfc10b895580 ]

It is still possible that we pin movable CMA pages if there are
isolation errors and cma_page_list stays empty when we check again.

Check for isolation errors, and return success only when there are no
isolation errors, and cma_page_list is empty after checking.

Because isolation errors are transient, we retry indefinitely.

Link: https://lkml.kernel.org/r/20210215161349.246722-5-pasha.tatashin@soleen.com
Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region")
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 | 60 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 34 insertions(+), 26 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 0fa8d88eb7ba..c2826f3afe72 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1561,8 +1561,8 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 					struct vm_area_struct **vmas,
 					unsigned int gup_flags)
 {
-	unsigned long i;
-	bool drain_allow = true;
+	unsigned long i, isolation_error_count;
+	bool drain_allow;
 	LIST_HEAD(cma_page_list);
 	long ret = nr_pages;
 	struct page *prev_head, *head;
@@ -1573,6 +1573,8 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
 
 check_again:
 	prev_head = NULL;
+	isolation_error_count = 0;
+	drain_allow = true;
 	for (i = 0; i < nr_pages; i++) {
 		head = compound_head(pages[i]);
 		if (head == prev_head)
@@ -1584,25 +1586,35 @@ check_again:
 		 * of the CMA zone if possible.
 		 */
 		if (is_migrate_cma_page(head)) {
-			if (PageHuge(head))
-				isolate_huge_page(head, &cma_page_list);
-			else {
+			if (PageHuge(head)) {
+				if (!isolate_huge_page(head, &cma_page_list))
+					isolation_error_count++;
+			} else {
 				if (!PageLRU(head) && drain_allow) {
 					lru_add_drain_all();
 					drain_allow = false;
 				}
 
-				if (!isolate_lru_page(head)) {
-					list_add_tail(&head->lru, &cma_page_list);
-					mod_node_page_state(page_pgdat(head),
-							    NR_ISOLATED_ANON +
-							    page_is_file_lru(head),
-							    thp_nr_pages(head));
+				if (isolate_lru_page(head)) {
+					isolation_error_count++;
+					continue;
 				}
+				list_add_tail(&head->lru, &cma_page_list);
+				mod_node_page_state(page_pgdat(head),
+						    NR_ISOLATED_ANON +
+						    page_is_file_lru(head),
+						    thp_nr_pages(head));
 			}
 		}
 	}
 
+	/*
+	 * If list is empty, and no isolation errors, means that all pages are
+	 * in the correct zone.
+	 */
+	if (list_empty(&cma_page_list) && !isolation_error_count)
+		return ret;
+
 	if (!list_empty(&cma_page_list)) {
 		/*
 		 * drop the above get_user_pages reference.
@@ -1622,23 +1634,19 @@ check_again:
 			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
-		 * earlier.
-		 */
-		ret = __get_user_pages_locked(mm, start, nr_pages,
-						   pages, vmas, NULL,
-						   gup_flags);
-
-		if (ret > 0) {
-			nr_pages = ret;
-			drain_allow = true;
-			goto check_again;
-		}
+		/* We unpinned pages before migration, pin them again */
+		ret = __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+					      NULL, gup_flags);
+		if (ret <= 0)
+			return ret;
+		nr_pages = ret;
 	}
 
-	return ret;
+	/*
+	 * check again because pages were unpinned, and we also might have
+	 * had isolation errors and need more pages to migrate.
+	 */
+	goto check_again;
 }
 #else
 static long check_and_migrate_cma_pages(struct mm_struct *mm,
-- 
2.30.2