mm: Account dirty folios properly during splits

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: 65476e358aca ("mm/filemap: Allow large folios to be added to the page cache")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 834f288b376909c351fc2a21d77e200f8e83a802..15965084816d3cef7701ccbf42c8650a0ffb394b 100644 (file)
--- 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>
@@ -2440,11 +2441,15 @@ 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);