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From:   David Hildenbrand <david@redhat.com>
To:     linux-kernel@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        John Hubbard <jhubbard@nvidia.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Yang Shi <shy828301@gmail.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
        Michal Hocko <mhocko@kernel.org>,
        Nadav Amit <namit@vmware.com>, Rik van Riel <riel@surriel.com>,
        Roman Gushchin <guro@fb.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Peter Xu <peterx@redhat.com>,
        Donald Dutile <ddutile@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Oleg Nesterov <oleg@redhat.com>, Jan Kara <jack@suse.cz>,
        Liang Zhang <zhangliang5@huawei.com>,
        Pedro Gomes <pedrodemargomes@gmail.com>,
        Oded Gabbay <oded.gabbay@gmail.com>, linux-mm@kvack.org,
        David Hildenbrand <david@redhat.com>
Subject: [PATCH v4 10/17] mm/huge_memory: remove outdated VM_WARN_ON_ONCE_PAGE from unmap_page()
Date:   Thu, 28 Apr 2022 10:34:34 +0200
Message-Id: <20220428083441.37290-11-david@redhat.com>
In-Reply-To: <20220428083441.37290-1-david@redhat.com>
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We can already theoretically fail to unmap (still having page_mapped()) in
case arch_unmap_one() fails, which can happen on sparc. Failures to
unmap are handled gracefully, just as if there are other references on
the target page: freezing the refcount in split_huge_page_to_list()
will fail if still mapped and we'll simply remap.

In commit 504e070dc08f ("mm: thp: replace DEBUG_VM BUG with VM_WARN when
unmap fails for split") we already converted to VM_WARN_ON_ONCE_PAGE,
let's get rid of it completely now.

This is a preparation for making try_to_migrate() fail on anonymous pages
with GUP pins, which will make this VM_WARN_ON_ONCE_PAGE trigger more
frequently.

Reported-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/huge_memory.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 04c9446b87a8..cb5bcd833d9e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2240,8 +2240,6 @@ static void unmap_page(struct page *page)
 		try_to_migrate(folio, ttu_flags);
 	else
 		try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
-
-	VM_WARN_ON_ONCE_PAGE(page_mapped(page), page);
 }
 
 static void remap_page(struct folio *folio, unsigned long nr)
-- 
2.35.1