dm crypt: account large pages in cc->n_allocated_pages

The commit 5054e77 ("dm crypt: allocate compound pages if
possible") changed dm-crypt to use compound pages to improve
performance. Unfortunately, there was an oversight: the allocation of
compound pages was not accounted at all. Normal pages are accounted in
a percpu counter cc->n_allocated_pages and dm-crypt is limited to
allocate at most 2% of memory. Because compound pages were not
accounted at all, dm-crypt could allocate memory over the 2% limit.

Fix this by adding the accounting of compound pages, so that memory
consumption of dm-crypt is properly limited.

Signed-off-by: Mikulas Patocka <[email protected]>
Fixes: 5054e77 ("dm crypt: allocate compound pages if possible")
Cc: [email protected]	# v6.5+
Signed-off-by: Mike Snitzer <[email protected]>

Author: Mikulas Patocka

drivers/md/dm-crypt.c

@@ -1692,11 +1692,17 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size)
 		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--;
 		}
 
@@ -1734,10 +1740,13 @@ static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)
 
 	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);
+			}
 		}
 	}
 }