// 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/bootmem.h>

  #include <linux/printk.h>

  #include <asm/tlbflush.h>

  #include <trace/events/block.h>

  #include "blk.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, isa_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;
  }

  #if defined(CONFIG_HIGHMEM)

  static __init int init_emergency_pool(void)
  {

  	int ret;

  #if defined(CONFIG_HIGHMEM) && !defined(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
  ", POOL_SIZE);

  	init_bounce_bioset();

  	return 0;
  }
  
  __initcall(init_emergency_pool);

  #endif

  #ifdef CONFIG_HIGHMEM

  /*
   * highmem version, map in to vec
   */
  static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
  {

  	unsigned char *vto;

  	vto = kmap_atomic(to->bv_page);

  	memcpy(vto + to->bv_offset, vfrom, to->bv_len);

  	kunmap_atomic(vto);

  }
  
  #else /* CONFIG_HIGHMEM */
  
  #define bounce_copy_vec(to, vfrom)	\
  	memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
  
  #endif /* CONFIG_HIGHMEM */
  
  /*
   * allocate pages in the DMA region for the ISA pool
   */
  static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
  {
  	return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
  }

  static DEFINE_MUTEX(isa_mutex);

  /*
   * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
   * as the max address, so check if the pool has already been created.
   */
  int init_emergency_isa_pool(void)
  {

  	int ret;

  	mutex_lock(&isa_mutex);
  
  	if (mempool_initialized(&isa_page_pool)) {
  		mutex_unlock(&isa_mutex);

  		return 0;

  	}

  	ret = mempool_init(&isa_page_pool, ISA_POOL_SIZE, mempool_alloc_pages_isa,
  			   mempool_free_pages, (void *) 0);
  	BUG_ON(ret);

  	pr_info("isa pool size: %d pages
  ", ISA_POOL_SIZE);

  	init_bounce_bioset();
  	mutex_unlock(&isa_mutex);

  	return 0;
  }
  
  /*
   * 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)
  {
  	unsigned char *vfrom;

  	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
  			 */

  			vfrom = page_address(fromvec.bv_page) +

  				tovec.bv_offset;
  
  			bounce_copy_vec(&tovec, vfrom);
  			flush_dcache_page(tovec.bv_page);
  		}

  		bio_advance_iter(from, &from_iter, tovec.bv_len);

  	}
  }

  static void bounce_end_io(struct bio *bio, mempool_t *pool)

  {
  	struct bio *bio_orig = bio->bi_private;

  	struct bio_vec *bvec, orig_vec;

  	int i;

  	struct bvec_iter orig_iter = bio_orig->bi_iter;

  	/*
  	 * free up bounce indirect pages used
  	 */

  	bio_for_each_segment_all(bvec, bio, i) {

  		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, 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, &page_pool);

  }

  static void bounce_end_io_write_isa(struct bio *bio)

  {

  	bounce_end_io(bio, &isa_page_pool);

  }

  static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)

  {
  	struct bio *bio_orig = bio->bi_private;

  	if (!bio->bi_status)

  		copy_to_high_bio_irq(bio_orig, bio);

  	bounce_end_io(bio, pool);

  }

  static void bounce_end_io_read(struct bio *bio)

  {

  	__bounce_end_io_read(bio, &page_pool);

  }

  static void bounce_end_io_read_isa(struct bio *bio)

  {

  	__bounce_end_io_read(bio, &isa_page_pool);

  }

  static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
  		struct bio_set *bs)
  {
  	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_PAGES 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_PAGES.
  	 *
  	 *  - 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 on
  	 *    __bio_clone_fast() anyways.
  	 */
  
  	bio = bio_alloc_bioset(gfp_mask, bio_segments(bio_src), bs);
  	if (!bio)
  		return NULL;
  	bio->bi_disk		= bio_src->bi_disk;
  	bio->bi_opf		= bio_src->bi_opf;

  	bio->bi_ioprio		= bio_src->bi_ioprio;

  	bio->bi_write_hint	= bio_src->bi_write_hint;
  	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;
  	case REQ_OP_WRITE_SAME:
  		bio->bi_io_vec[bio->bi_vcnt++] = bio_src->bi_io_vec[0];
  		break;
  	default:
  		bio_for_each_segment(bv, bio_src, iter)
  			bio->bi_io_vec[bio->bi_vcnt++] = bv;
  		break;
  	}
  
  	if (bio_integrity(bio_src)) {
  		int ret;
  
  		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
  		if (ret < 0) {
  			bio_put(bio);
  			return NULL;
  		}
  	}
  
  	bio_clone_blkcg_association(bio, bio_src);
  
  	return bio;
  }

  static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,

  			       mempool_t *pool)

  {

  	struct bio *bio;
  	int rw = bio_data_dir(*bio_orig);

  	struct bio_vec *to, from;
  	struct bvec_iter iter;

  	unsigned i = 0;
  	bool bounce = false;
  	int sectors = 0;

  	bool passthrough = bio_is_passthrough(*bio_orig);

  	bio_for_each_segment(from, *bio_orig, iter) {
  		if (i++ < BIO_MAX_PAGES)
  			sectors += from.bv_len >> 9;

  		if (page_to_pfn(from.bv_page) > q->limits.bounce_pfn)

  			bounce = true;
  	}
  	if (!bounce)
  		return;

  	if (!passthrough && sectors < bio_sectors(*bio_orig)) {

  		bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);

  		bio_chain(bio, *bio_orig);
  		generic_make_request(*bio_orig);
  		*bio_orig = bio;
  	}

  	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :

  			&bounce_bio_set);

  	bio_for_each_segment_all(to, bio, i) {

  		struct page *page = to->bv_page;

  		if (page_to_pfn(page) <= q->limits.bounce_pfn)

  			continue;

  		to->bv_page = mempool_alloc(pool, q->bounce_gfp);

  		inc_zone_page_state(to->bv_page, NR_BOUNCE);

  
  		if (rw == WRITE) {
  			char *vto, *vfrom;

  			flush_dcache_page(page);

  			vto = page_address(to->bv_page) + to->bv_offset;

  			vfrom = kmap_atomic(page) + to->bv_offset;

  			memcpy(vto, vfrom, to->bv_len);

  			kunmap_atomic(vfrom);

  		}
  	}

  	trace_block_bio_bounce(q, *bio_orig);

  	bio->bi_flags |= (1 << BIO_BOUNCED);

  	if (pool == &page_pool) {

  		bio->bi_end_io = bounce_end_io_write;
  		if (rw == READ)
  			bio->bi_end_io = bounce_end_io_read;
  	} else {
  		bio->bi_end_io = bounce_end_io_write_isa;
  		if (rw == READ)
  			bio->bi_end_io = bounce_end_io_read_isa;
  	}
  
  	bio->bi_private = *bio_orig;
  	*bio_orig = bio;
  }

  void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)

  {
  	mempool_t *pool;
  
  	/*

  	 * Data-less bio, nothing to bounce
  	 */

  	if (!bio_has_data(*bio_orig))

  		return;
  
  	/*

  	 * for non-isa bounce case, just check if the bounce pfn is equal
  	 * to or bigger than the highest pfn in the system -- in that case,
  	 * don't waste time iterating over bio segments
  	 */
  	if (!(q->bounce_gfp & GFP_DMA)) {

  		if (q->limits.bounce_pfn >= blk_max_pfn)

  			return;

  		pool = &page_pool;

  	} else {

  		BUG_ON(!mempool_initialized(&isa_page_pool));
  		pool = &isa_page_pool;

  	}

  	/*
  	 * slow path
  	 */

  	__blk_queue_bounce(q, bio_orig, pool);

  }