block/bounce.c - kernel/msm-5.4 - Gitiles

 // 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/memblock.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\n", 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\n", 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_blkg_association(bio, bio_src);
 	blkcg_bio_issue_init(bio);

 	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);
 }
	// 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/memblock.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\n", 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\n", 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_blkg_association(bio, bio_src);
	blkcg_bio_issue_init(bio);

	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);
	}