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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, Dave Chinner <dchinner@redhat.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.18 0401/1095] mm: Account dirty folios properly during splits
Date:   Mon, 15 Aug 2022 19:56:40 +0200
Message-Id: <20220815180446.282386990@linuxfoundation.org>
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From: Matthew Wilcox (Oracle) <willy@infradead.org>

[ Upstream commit fb5c2029f8221e904e604938171c4a8ef169aadb ]

If the last folio in a file is split as a result of truncation,
we simply clear the dirty bits for the pages we're discarding.
That causes NR_FILE_DIRTY (among other counters) to be thrown off
and eventually Linux will hang in balance_dirty_pages_ratelimited()

Reported-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Fixes: d68eccad3706 ("mm/filemap: Allow large folios to be added to the page cache")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/huge_memory.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b7d0697b1f26..e0c1cf3168d7 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -18,6 +18,7 @@
 #include <linux/shrinker.h>
 #include <linux/mm_inline.h>
 #include <linux/swapops.h>
+#include <linux/backing-dev.h>
 #include <linux/dax.h>
 #include <linux/khugepaged.h>
 #include <linux/freezer.h>
@@ -2389,11 +2390,15 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 		__split_huge_page_tail(head, i, lruvec, list);
 		/* Some pages can be beyond EOF: drop them from page cache */
 		if (head[i].index >= end) {
-			ClearPageDirty(head + i);
-			__delete_from_page_cache(head + i, NULL);
+			struct folio *tail = page_folio(head + i);
+
 			if (shmem_mapping(head->mapping))
 				shmem_uncharge(head->mapping->host, 1);
-			put_page(head + i);
+			else if (folio_test_clear_dirty(tail))
+				folio_account_cleaned(tail,
+					inode_to_wb(folio->mapping->host));
+			__filemap_remove_folio(tail, NULL);
+			folio_put(tail);
 		} else if (!PageAnon(page)) {
 			__xa_store(&head->mapping->i_pages, head[i].index,
 					head + i, 0);
-- 
2.35.1