[PATCH] mm/vmscan.c:shrink_folio_list(): save a tabstop

[PATCH] mm/vmscan.c:shrink_folio_list(): save a tabstop

[Andrew Morton]

An effort to make shrink_folio_list() less painful.


From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm/vmscan.c:shrink_folio_list(): save a tabstop 
Date: Mon Dec 15 11:05:56 AM PST 2025

We have some needlessly deep indentation in this huge function due to

	if (expr1) {
		if (expr2) {
			...
		}
	}

Convert this to

	if (expr1 && expr2) {
		...
	}

Also, reflow that big block comment to fit in 80 cols.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   96 +++++++++++++++++++++++++-------------------------
 1 file changed, 48 insertions(+), 48 deletions(-)

--- a/mm/vmscan.c~mm-vmscanc-shrink_folio_list-save-a-tabstop
+++ a/mm/vmscan.c
@@ -1276,58 +1276,58 @@ retry:
 		 * Try to allocate it some swap space here.
 		 * Lazyfree folio could be freed directly
 		 */
-		if (folio_test_anon(folio) && folio_test_swapbacked(folio)) {
-			if (!folio_test_swapcache(folio)) {
-				if (!(sc->gfp_mask & __GFP_IO))
-					goto keep_locked;
-				if (folio_maybe_dma_pinned(folio))
-					goto keep_locked;
-				if (folio_test_large(folio)) {
-					/* cannot split folio, skip it */
-					if (folio_expected_ref_count(folio) !=
-					    folio_ref_count(folio) - 1)
-						goto activate_locked;
-					/*
-					 * Split partially mapped folios right away.
-					 * We can free the unmapped pages without IO.
-					 */
-					if (data_race(!list_empty(&folio->_deferred_list) &&
-					    folio_test_partially_mapped(folio)) &&
-					    split_folio_to_list(folio, folio_list))
-						goto activate_locked;
-				}
-				if (folio_alloc_swap(folio)) {
-					int __maybe_unused order = folio_order(folio);
+		if (folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+				!folio_test_swapcache(folio)) {
+			if (!(sc->gfp_mask & __GFP_IO))
+				goto keep_locked;
+			if (folio_maybe_dma_pinned(folio))
+				goto keep_locked;
+			if (folio_test_large(folio)) {
+				/* cannot split folio, skip it */
+				if (folio_expected_ref_count(folio) !=
+				    folio_ref_count(folio) - 1)
+					goto activate_locked;
+				/*
+				 * Split partially mapped folios right away.
+				 * We can free the unmapped pages without IO.
+				 */
+				if (data_race(!list_empty(&folio->_deferred_list) &&
+				    folio_test_partially_mapped(folio)) &&
+				    split_folio_to_list(folio, folio_list))
+					goto activate_locked;
+			}
+			if (folio_alloc_swap(folio)) {
+				int __maybe_unused order = folio_order(folio);
 
-					if (!folio_test_large(folio))
-						goto activate_locked_split;
-					/* Fallback to swap normal pages */
-					if (split_folio_to_list(folio, folio_list))
-						goto activate_locked;
+				if (!folio_test_large(folio))
+					goto activate_locked_split;
+				/* Fallback to swap normal pages */
+				if (split_folio_to_list(folio, folio_list))
+					goto activate_locked;
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-					if (nr_pages >= HPAGE_PMD_NR) {
-						count_memcg_folio_events(folio,
-							THP_SWPOUT_FALLBACK, 1);
-						count_vm_event(THP_SWPOUT_FALLBACK);
-					}
-#endif
-					count_mthp_stat(order, MTHP_STAT_SWPOUT_FALLBACK);
-					if (folio_alloc_swap(folio))
-						goto activate_locked_split;
+				if (nr_pages >= HPAGE_PMD_NR) {
+					count_memcg_folio_events(folio,
+						THP_SWPOUT_FALLBACK, 1);
+					count_vm_event(THP_SWPOUT_FALLBACK);
 				}
-				/*
-				 * Normally the folio will be dirtied in unmap because its
-				 * pte should be dirty. A special case is MADV_FREE page. The
-				 * page's pte could have dirty bit cleared but the folio's
-				 * SwapBacked flag is still set because clearing the dirty bit
-				 * and SwapBacked flag has no lock protected. For such folio,
-				 * unmap will not set dirty bit for it, so folio reclaim will
-				 * not write the folio out. This can cause data corruption when
-				 * the folio is swapped in later. Always setting the dirty flag
-				 * for the folio solves the problem.
-				 */
-				folio_mark_dirty(folio);
+#endif
+				count_mthp_stat(order, MTHP_STAT_SWPOUT_FALLBACK);
+				if (folio_alloc_swap(folio))
+					goto activate_locked_split;
 			}
+			/*
+			 * Normally the folio will be dirtied in unmap because
+			 * its pte should be dirty. A special case is MADV_FREE
+			 * page. The page's pte could have dirty bit cleared but
+			 * the folio's SwapBacked flag is still set because
+			 * clearing the dirty bit and SwapBacked flag has no
+			 * lock protected. For such folio, unmap will not set
+			 * dirty bit for it, so folio reclaim will not write the
+			 * folio out. This can cause data corruption when the
+			 * folio is swapped in later. Always setting the dirty
+			 * flag for the folio solves the problem.
+			 */
+			folio_mark_dirty(folio);
 		}
 
 		/*
_