dm-crypt: account large pages in cc->n_allocated_pages

Commit Message

Mikulas Patocka Oct. 31, 2023, 6:12 p.m. UTC

The commit 5054e778fcd9c changed dm-crypt to use compound pages to improve
performance. Unfortunatelly, there was an oversight - normal pages are
accounted in a percpu counter cc->n_allocated_pages and dm-crypt is
limited to allocate at most 2% of memory. Compound pages were not
accounted at all. So, dm-crypt could allocate memory over the limit.

This patch adds the accounting of compound pages, so that memory
consumption of dm-crypt is properly limited.

Signed-off-by: Mikulas Patocka <[e-mail]>
Cc: [e-mail]	# v6.5
Fixes: 5054e778fcd9c ("dm crypt: allocate compound pages if possible")

---
 drivers/md/dm-crypt.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Patch

Index: linux-stable/drivers/md/dm-crypt.c
===================================================================
--- linux-stable.orig/drivers/md/dm-crypt.c	2023-10-31 19:11:25.000000000 +0100
+++ linux-stable/drivers/md/dm-crypt.c	2023-10-31 19:11:46.000000000 +0100
@@ -1700,11 +1700,17 @@  retry:
 		order = min(order, remaining_order);
 
 		while (order > 0) {
+			if (unlikely(percpu_counter_read_positive(&cc->n_allocated_pages) +
+					(1 << order) > dm_crypt_pages_per_client))
+				goto decrease_order;
 			pages = alloc_pages(gfp_mask
 				| __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN | __GFP_COMP,
 				order);
-			if (likely(pages != NULL))
+			if (likely(pages != NULL)) {
+				percpu_counter_add(&cc->n_allocated_pages, 1 << order);
 				goto have_pages;
+			}
+decrease_order:
 			order--;
 		}
 
@@ -1742,10 +1748,13 @@  static void crypt_free_buffer_pages(stru
 
 	if (clone->bi_vcnt > 0) { /* bio_for_each_folio_all crashes with an empty bio */
 		bio_for_each_folio_all(fi, clone) {
-			if (folio_test_large(fi.folio))
+			if (folio_test_large(fi.folio)) {
+				percpu_counter_sub(&cc->n_allocated_pages,
+						1 << folio_order(fi.folio));
 				folio_put(fi.folio);
-			else
+			} else {
 				mempool_free(&fi.folio->page, &cc->page_pool);
+			}
 		}
 	}
 }