1 files changed, 268 insertions, 0 deletions
diff --git a/block/bounce.c b/block/bounce.c
new file mode 100644
index 000000000..7cfcb242f
--- /dev/null
+++ b/block/bounce.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0
+/* bounce buffer handling for block devices
+ *
+ * - Split from highmem.c
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/export.h>
+#include <linux/swap.h>
+#include <linux/gfp.h>
+#include <linux/bio.h>
+#include <linux/pagemap.h>
+#include <linux/mempool.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/highmem.h>
+#include <linux/printk.h>
+#include <asm/tlbflush.h>
+
+#include <trace/events/block.h>
+#include "blk.h"
+#include "blk-cgroup.h"
+
+#define POOL_SIZE	64
+#define ISA_POOL_SIZE	16
+
+static struct bio_set bounce_bio_set, bounce_bio_split;
+static mempool_t page_pool;
+
+static void init_bounce_bioset(void)
+{
+	static bool bounce_bs_setup;
+	int ret;
+
+	if (bounce_bs_setup)
+		return;
+
+	ret = bioset_init(&bounce_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
+	BUG_ON(ret);
+	if (bioset_integrity_create(&bounce_bio_set, BIO_POOL_SIZE))
+		BUG_ON(1);
+
+	ret = bioset_init(&bounce_bio_split, BIO_POOL_SIZE, 0, 0);
+	BUG_ON(ret);
+	bounce_bs_setup = true;
+}
+
+static __init int init_emergency_pool(void)
+{
+	int ret;
+
+#ifndef CONFIG_MEMORY_HOTPLUG
+	if (max_pfn <= max_low_pfn)
+		return 0;
+#endif
+
+	ret = mempool_init_page_pool(&page_pool, POOL_SIZE, 0);
+	BUG_ON(ret);
+	pr_info("pool size: %d pages\n", POOL_SIZE);
+
+	init_bounce_bioset();
+	return 0;
+}
+
+__initcall(init_emergency_pool);
+
+/*
+ * Simple bounce buffer support for highmem pages. Depending on the
+ * queue gfp mask set, *to may or may not be a highmem page. kmap it
+ * always, it will do the Right Thing
+ */
+static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
+{
+	struct bio_vec tovec, fromvec;
+	struct bvec_iter iter;
+	/*
+	 * The bio of @from is created by bounce, so we can iterate
+	 * its bvec from start to end, but the @from->bi_iter can't be
+	 * trusted because it might be changed by splitting.
+	 */
+	struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;
+
+	bio_for_each_segment(tovec, to, iter) {
+		fromvec = bio_iter_iovec(from, from_iter);
+		if (tovec.bv_page != fromvec.bv_page) {
+			/*
+			 * fromvec->bv_offset and fromvec->bv_len might have
+			 * been modified by the block layer, so use the original
+			 * copy, bounce_copy_vec already uses tovec->bv_len
+			 */
+			memcpy_to_bvec(&tovec, page_address(fromvec.bv_page) +
+				       tovec.bv_offset);
+		}
+		bio_advance_iter(from, &from_iter, tovec.bv_len);
+	}
+}
+
+static void bounce_end_io(struct bio *bio)
+{
+	struct bio *bio_orig = bio->bi_private;
+	struct bio_vec *bvec, orig_vec;
+	struct bvec_iter orig_iter = bio_orig->bi_iter;
+	struct bvec_iter_all iter_all;
+
+	/*
+	 * free up bounce indirect pages used
+	 */
+	bio_for_each_segment_all(bvec, bio, iter_all) {
+		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
+		if (bvec->bv_page != orig_vec.bv_page) {
+			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
+			mempool_free(bvec->bv_page, &page_pool);
+		}
+		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
+	}
+
+	bio_orig->bi_status = bio->bi_status;
+	bio_endio(bio_orig);
+	bio_put(bio);
+}
+
+static void bounce_end_io_write(struct bio *bio)
+{
+	bounce_end_io(bio);
+}
+
+static void bounce_end_io_read(struct bio *bio)
+{
+	struct bio *bio_orig = bio->bi_private;
+
+	if (!bio->bi_status)
+		copy_to_high_bio_irq(bio_orig, bio);
+
+	bounce_end_io(bio);
+}
+
+static struct bio *bounce_clone_bio(struct bio *bio_src)
+{
+	struct bvec_iter iter;
+	struct bio_vec bv;
+	struct bio *bio;
+
+	/*
+	 * Pre immutable biovecs, __bio_clone() used to just do a memcpy from
+	 * bio_src->bi_io_vec to bio->bi_io_vec.
+	 *
+	 * We can't do that anymore, because:
+	 *
+	 *  - The point of cloning the biovec is to produce a bio with a biovec
+	 *    the caller can modify: bi_idx and bi_bvec_done should be 0.
+	 *
+	 *  - The original bio could've had more than BIO_MAX_VECS biovecs; if
+	 *    we tried to clone the whole thing bio_alloc_bioset() would fail.
+	 *    But the clone should succeed as long as the number of biovecs we
+	 *    actually need to allocate is fewer than BIO_MAX_VECS.
+	 *
+	 *  - Lastly, bi_vcnt should not be looked at or relied upon by code
+	 *    that does not own the bio - reason being drivers don't use it for
+	 *    iterating over the biovec anymore, so expecting it to be kept up
+	 *    to date (i.e. for clones that share the parent biovec) is just
+	 *    asking for trouble and would force extra work.
+	 */
+	bio = bio_alloc_bioset(bio_src->bi_bdev, bio_segments(bio_src),
+			       bio_src->bi_opf, GFP_NOIO, &bounce_bio_set);
+	if (bio_flagged(bio_src, BIO_REMAPPED))
+		bio_set_flag(bio, BIO_REMAPPED);
+	bio->bi_ioprio		= bio_src->bi_ioprio;
+	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
+	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
+
+	switch (bio_op(bio)) {
+	case REQ_OP_DISCARD:
+	case REQ_OP_SECURE_ERASE:
+	case REQ_OP_WRITE_ZEROES:
+		break;
+	default:
+		bio_for_each_segment(bv, bio_src, iter)
+			bio->bi_io_vec[bio->bi_vcnt++] = bv;
+		break;
+	}
+
+	if (bio_crypt_clone(bio, bio_src, GFP_NOIO) < 0)
+		goto err_put;
+
+	if (bio_integrity(bio_src) &&
+	    bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0)
+		goto err_put;
+
+	bio_clone_blkg_association(bio, bio_src);
+
+	return bio;
+
+err_put:
+	bio_put(bio);
+	return NULL;
+}
+
+struct bio *__blk_queue_bounce(struct bio *bio_orig, struct request_queue *q)
+{
+	struct bio *bio;
+	int rw = bio_data_dir(bio_orig);
+	struct bio_vec *to, from;
+	struct bvec_iter iter;
+	unsigned i = 0, bytes = 0;
+	bool bounce = false;
+	int sectors;
+
+	bio_for_each_segment(from, bio_orig, iter) {
+		if (i++ < BIO_MAX_VECS)
+			bytes += from.bv_len;
+		if (PageHighMem(from.bv_page))
+			bounce = true;
+	}
+	if (!bounce)
+		return bio_orig;
+
+	/*
+	 * Individual bvecs might not be logical block aligned. Round down
+	 * the split size so that each bio is properly block size aligned,
+	 * even if we do not use the full hardware limits.
+	 */
+	sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >>
+			SECTOR_SHIFT;
+	if (sectors < bio_sectors(bio_orig)) {
+		bio = bio_split(bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
+		bio_chain(bio, bio_orig);
+		submit_bio_noacct(bio_orig);
+		bio_orig = bio;
+	}
+	bio = bounce_clone_bio(bio_orig);
+
+	/*
+	 * Bvec table can't be updated by bio_for_each_segment_all(),
+	 * so retrieve bvec from the table directly. This way is safe
+	 * because the 'bio' is single-page bvec.
+	 */
+	for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
+		struct page *bounce_page;
+
+		if (!PageHighMem(to->bv_page))
+			continue;
+
+		bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
+		inc_zone_page_state(bounce_page, NR_BOUNCE);
+
+		if (rw == WRITE) {
+			flush_dcache_page(to->bv_page);
+			memcpy_from_bvec(page_address(bounce_page), to);
+		}
+		to->bv_page = bounce_page;
+	}
+
+	trace_block_bio_bounce(bio_orig);
+
+	bio->bi_flags |= (1 << BIO_BOUNCED);
+
+	if (rw == READ)
+		bio->bi_end_io = bounce_end_io_read;
+	else
+		bio->bi_end_io = bounce_end_io_write;
+
+	bio->bi_private = bio_orig;
+	return bio;
+}