[RFC PATCH 03/28] block: Warn on mis-use of dma-direct bios

[Logan Gunthorpe]

This is a result of an audit of users of 'bi_io_vec'. A number of
warnings and blocking conditions are added to ensure dma-direct bios
are not incorrectly accessing the 'bi_io_vec' when they should access
the 'bi_dma_vec'. These are largely just protecting against mis-uses
in future development so depending on taste and public opinion some
or all of these checks may not be necessary.

A few other issues with dma-direct bios will be tackled in subsequent
patches.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 block/bio.c      | 33 +++++++++++++++++++++++++++++++++
 block/blk-core.c |  3 +++
 2 files changed, 36 insertions(+)

diff --git a/block/bio.c b/block/bio.c
index 683cbb40f051..6998fceddd36 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -525,6 +525,9 @@ void zero_fill_bio_iter(struct bio *bio, struct bvec_iter start)
 	struct bio_vec bv;
 	struct bvec_iter iter;
 
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return;
+
 	__bio_for_each_segment(bv, bio, iter, start) {
 		char *data = bvec_kmap_irq(&bv, &flags);
 		memset(data, 0, bv.bv_len);
@@ -707,6 +710,8 @@ static int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
 	 */
 	if (unlikely(bio_flagged(bio, BIO_CLONED)))
 		return 0;
+	if (unlikely(bio_is_dma_direct(bio)))
+		return 0;
 
 	if (((bio->bi_iter.bi_size + len) >> 9) > queue_max_hw_sectors(q))
 		return 0;
@@ -783,6 +788,8 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
 {
 	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 		return false;
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return false;
 
 	if (bio->bi_vcnt > 0) {
 		struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
@@ -814,6 +821,7 @@ void __bio_add_page(struct bio *bio, struct page *page,
 
 	WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
 	WARN_ON_ONCE(bio_full(bio));
+	WARN_ON_ONCE(bio_is_dma_direct(bio));
 
 	bv->bv_page = page;
 	bv->bv_offset = off;
@@ -851,6 +859,8 @@ static void bio_get_pages(struct bio *bio)
 	struct bvec_iter_all iter_all;
 	struct bio_vec *bvec;
 
+	WARN_ON_ONCE(bio_is_dma_direct(bio));
+
 	bio_for_each_segment_all(bvec, bio, iter_all)
 		get_page(bvec->bv_page);
 }
@@ -956,6 +966,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 
 	if (WARN_ON_ONCE(bio->bi_vcnt))
 		return -EINVAL;
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return -EINVAL;
 
 	do {
 		if (is_bvec)
@@ -1029,6 +1041,9 @@ void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
 	void *src_p, *dst_p;
 	unsigned bytes;
 
+	if (WARN_ON_ONCE(bio_is_dma_direct(src) || bio_is_dma_direct(dst)))
+		return;
+
 	while (src_iter->bi_size && dst_iter->bi_size) {
 		src_bv = bio_iter_iovec(src, *src_iter);
 		dst_bv = bio_iter_iovec(dst, *dst_iter);
@@ -1143,6 +1158,9 @@ static int bio_copy_from_iter(struct bio *bio, struct iov_iter *iter)
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return -EINVAL;
+
 	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ssize_t ret;
 
@@ -1174,6 +1192,9 @@ static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter)
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return -EINVAL;
+
 	bio_for_each_segment_all(bvec, bio, iter_all) {
 		ssize_t ret;
 
@@ -1197,6 +1218,9 @@ void bio_free_pages(struct bio *bio)
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
+	if (WARN_ON_ONCE(bio_is_dma_direct(bio)))
+		return;
+
 	bio_for_each_segment_all(bvec, bio, iter_all)
 		__free_page(bvec->bv_page);
 }
@@ -1653,6 +1677,9 @@ void bio_set_pages_dirty(struct bio *bio)
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
 
+	if (unlikely(bio_is_dma_direct(bio)))
+		return;
+
 	bio_for_each_segment_all(bvec, bio, iter_all) {
 		if (!PageCompound(bvec->bv_page))
 			set_page_dirty_lock(bvec->bv_page);
@@ -1704,6 +1731,9 @@ void bio_check_pages_dirty(struct bio *bio)
 	unsigned long flags;
 	struct bvec_iter_all iter_all;
 
+	if (unlikely(bio_is_dma_direct(bio)))
+		return;
+
 	bio_for_each_segment_all(bvec, bio, iter_all) {
 		if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))
 			goto defer;
@@ -1777,6 +1807,9 @@ void bio_flush_dcache_pages(struct bio *bi)
 	struct bio_vec bvec;
 	struct bvec_iter iter;
 
+	if (unlikely(bio_is_dma_direct(bi)))
+		return;
+
 	bio_for_each_segment(bvec, bi, iter)
 		flush_dcache_page(bvec.bv_page);
 }
diff --git a/block/blk-core.c b/block/blk-core.c
index 8340f69670d8..ea152d54c7ce 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1467,6 +1467,9 @@ void rq_flush_dcache_pages(struct request *rq)
 	struct req_iterator iter;
 	struct bio_vec bvec;
 
+	if (unlikely(blk_rq_is_dma_direct(rq)))
+		return;
+
 	rq_for_each_segment(bvec, rq, iter)
 		flush_dcache_page(bvec.bv_page);
 }
-- 
2.20.1