Commit 5054e778 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm crypt: allocate compound pages if possible 

It was reported that allocating pages for the write buffer in dm-crypt
causes measurable overhead [1].

Change dm-crypt to allocate compound pages if they are available. If
not, fall back to the mempool.

[1] https://listman.redhat.com/archives/dm-devel/2023-February/053284.html



Suggested-by: default avatarMatthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 24516565

drivers/md/dm-crypt.c

+35 −14
Original line number Diff line number Diff line
@@ -1661,6 +1661,9 @@ static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone); 
 * In order to not degrade performance with excessive locking, we try

 * non-blocking allocations without a mutex first but on failure we fallback

 * to blocking allocations with a mutex.

 *

 * In order to reduce allocation overhead, we try to allocate compound pages in

 * the first pass. If they are not available, we fall back to the mempool.

 */

static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size)

{
@@ -1668,8 +1671,8 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size) 
	struct bio *clone;

	unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

	gfp_t gfp_mask = GFP_NOWAIT | __GFP_HIGHMEM;

	unsigned int i, len, remaining_size;

	struct page *page;

	unsigned int remaining_size;

	unsigned int order = MAX_ORDER - 1;



retry:

	if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))
@@ -1682,19 +1685,34 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size) 


	remaining_size = size;



	for (i = 0; i < nr_iovecs; i++) {

		page = mempool_alloc(&cc->page_pool, gfp_mask);

		if (!page) {

	while (remaining_size) {

		struct page *pages;

		unsigned size_to_add;

		unsigned remaining_order = __fls((remaining_size + PAGE_SIZE - 1) >> PAGE_SHIFT);

		order = min(order, remaining_order);



		while (order > 0) {

			pages = alloc_pages(gfp_mask

				| __GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN | __GFP_COMP,

				order);

			if (likely(pages != NULL))

				goto have_pages;

			order--;

		}



		pages = mempool_alloc(&cc->page_pool, gfp_mask);

		if (!pages) {

			crypt_free_buffer_pages(cc, clone);

			bio_put(clone);

			gfp_mask |= __GFP_DIRECT_RECLAIM;

			order = 0;

			goto retry;

		}



		len = (remaining_size > PAGE_SIZE) ? PAGE_SIZE : remaining_size;



		__bio_add_page(clone, page, len, 0);

		remaining_size -= len;

have_pages:

		size_to_add = min((unsigned)PAGE_SIZE << order, remaining_size);

		__bio_add_page(clone, pages, size_to_add, 0);

		remaining_size -= size_to_add;

	}



	/* Allocate space for integrity tags */
@@ -1712,12 +1730,15 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size) 


static void crypt_free_buffer_pages(struct crypt_config *cc, struct bio *clone)

{

	struct bio_vec *bv;

	struct bvec_iter_all iter_all;

	struct folio_iter fi;



	bio_for_each_segment_all(bv, clone, iter_all) {

		BUG_ON(!bv->bv_page);

		mempool_free(bv->bv_page, &cc->page_pool);

	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))

				folio_put(fi.folio);

			else

				mempool_free(&fi.folio->page, &cc->page_pool);

		}

	}

}