[PATCH] dm-crypt: account large pages in cc->n_allocated_pages

[Mikulas Patocka]

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 <mpato...@redhat.com>
Cc: sta...@vger.kernel.org      # v6.5
Fixes: 5054e778fcd9c ("dm crypt: allocate compound pages if possible")

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

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);
+                       }
                }
        }
 }