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  1// SPDX-License-Identifier: GPL-2.0
  2/* bounce buffer handling for block devices
  3 *
  4 * - Split from highmem.c
  5 */
  6
  7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8
  9#include <linux/mm.h>
 10#include <linux/export.h>
 11#include <linux/swap.h>
 12#include <linux/gfp.h>
 13#include <linux/bio.h>
 14#include <linux/pagemap.h>
 15#include <linux/mempool.h>
 16#include <linux/blkdev.h>
 17#include <linux/backing-dev.h>
 18#include <linux/init.h>
 19#include <linux/hash.h>
 20#include <linux/highmem.h>
 21#include <linux/bootmem.h>
 22#include <linux/printk.h>
 23#include <asm/tlbflush.h>
 24
 25#include <trace/events/block.h>
 26#include "blk.h"
 27
 28#define POOL_SIZE	64
 29#define ISA_POOL_SIZE	16
 30
 31static struct bio_set *bounce_bio_set, *bounce_bio_split;
 32static mempool_t *page_pool, *isa_page_pool;
 33
 34#if defined(CONFIG_HIGHMEM)
 35static __init int init_emergency_pool(void)
 36{
 37#if defined(CONFIG_HIGHMEM) && !defined(CONFIG_MEMORY_HOTPLUG)
 38	if (max_pfn <= max_low_pfn)
 39		return 0;
 40#endif
 41
 42	page_pool = mempool_create_page_pool(POOL_SIZE, 0);
 43	BUG_ON(!page_pool);
 44	pr_info("pool size: %d pages\n", POOL_SIZE);
 45
 46	bounce_bio_set = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
 47	BUG_ON(!bounce_bio_set);
 48	if (bioset_integrity_create(bounce_bio_set, BIO_POOL_SIZE))
 49		BUG_ON(1);
 50
 51	bounce_bio_split = bioset_create(BIO_POOL_SIZE, 0, 0);
 52	BUG_ON(!bounce_bio_split);
 53
 54	return 0;
 55}
 56
 57__initcall(init_emergency_pool);
 58#endif
 59
 60#ifdef CONFIG_HIGHMEM
 61/*
 62 * highmem version, map in to vec
 63 */
 64static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
 65{
 66	unsigned long flags;
 67	unsigned char *vto;
 68
 69	local_irq_save(flags);
 70	vto = kmap_atomic(to->bv_page);
 71	memcpy(vto + to->bv_offset, vfrom, to->bv_len);
 72	kunmap_atomic(vto);
 73	local_irq_restore(flags);
 74}
 75
 76#else /* CONFIG_HIGHMEM */
 77
 78#define bounce_copy_vec(to, vfrom)	\
 79	memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
 80
 81#endif /* CONFIG_HIGHMEM */
 82
 83/*
 84 * allocate pages in the DMA region for the ISA pool
 85 */
 86static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
 87{
 88	return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
 89}
 90
 91/*
 92 * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 93 * as the max address, so check if the pool has already been created.
 94 */
 95int init_emergency_isa_pool(void)
 96{
 97	if (isa_page_pool)
 98		return 0;
 99
100	isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
101				       mempool_free_pages, (void *) 0);
102	BUG_ON(!isa_page_pool);
103
104	pr_info("isa pool size: %d pages\n", ISA_POOL_SIZE);
105	return 0;
106}
107
108/*
109 * Simple bounce buffer support for highmem pages. Depending on the
110 * queue gfp mask set, *to may or may not be a highmem page. kmap it
111 * always, it will do the Right Thing
112 */
113static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
114{
115	unsigned char *vfrom;
116	struct bio_vec tovec, fromvec;
117	struct bvec_iter iter;
118	/*
119	 * The bio of @from is created by bounce, so we can iterate
120	 * its bvec from start to end, but the @from->bi_iter can't be
121	 * trusted because it might be changed by splitting.
122	 */
123	struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;
124
125	bio_for_each_segment(tovec, to, iter) {
126		fromvec = bio_iter_iovec(from, from_iter);
127		if (tovec.bv_page != fromvec.bv_page) {
128			/*
129			 * fromvec->bv_offset and fromvec->bv_len might have
130			 * been modified by the block layer, so use the original
131			 * copy, bounce_copy_vec already uses tovec->bv_len
132			 */
133			vfrom = page_address(fromvec.bv_page) +
134				tovec.bv_offset;
135
136			bounce_copy_vec(&tovec, vfrom);
137			flush_dcache_page(tovec.bv_page);
138		}
139		bio_advance_iter(from, &from_iter, tovec.bv_len);
140	}
141}
142
143static void bounce_end_io(struct bio *bio, mempool_t *pool)
144{
145	struct bio *bio_orig = bio->bi_private;
146	struct bio_vec *bvec, orig_vec;
147	int i;
148	struct bvec_iter orig_iter = bio_orig->bi_iter;
149
150	/*
151	 * free up bounce indirect pages used
152	 */
153	bio_for_each_segment_all(bvec, bio, i) {
154		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
155		if (bvec->bv_page != orig_vec.bv_page) {
156			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
157			mempool_free(bvec->bv_page, pool);
158		}
159		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
160	}
161
162	bio_orig->bi_status = bio->bi_status;
163	bio_endio(bio_orig);
164	bio_put(bio);
165}
166
167static void bounce_end_io_write(struct bio *bio)
168{
169	bounce_end_io(bio, page_pool);
170}
171
172static void bounce_end_io_write_isa(struct bio *bio)
173{
174
175	bounce_end_io(bio, isa_page_pool);
176}
177
178static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)
179{
180	struct bio *bio_orig = bio->bi_private;
181
182	if (!bio->bi_status)
183		copy_to_high_bio_irq(bio_orig, bio);
184
185	bounce_end_io(bio, pool);
186}
187
188static void bounce_end_io_read(struct bio *bio)
189{
190	__bounce_end_io_read(bio, page_pool);
191}
192
193static void bounce_end_io_read_isa(struct bio *bio)
194{
195	__bounce_end_io_read(bio, isa_page_pool);
196}
197
198static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
199			       mempool_t *pool)
200{
201	struct bio *bio;
202	int rw = bio_data_dir(*bio_orig);
203	struct bio_vec *to, from;
204	struct bvec_iter iter;
205	unsigned i = 0;
206	bool bounce = false;
207	int sectors = 0;
208	bool passthrough = bio_is_passthrough(*bio_orig);
209
210	bio_for_each_segment(from, *bio_orig, iter) {
211		if (i++ < BIO_MAX_PAGES)
212			sectors += from.bv_len >> 9;
213		if (page_to_pfn(from.bv_page) > q->limits.bounce_pfn)
214			bounce = true;
215	}
216	if (!bounce)
217		return;
218
219	if (!passthrough && sectors < bio_sectors(*bio_orig)) {
220		bio = bio_split(*bio_orig, sectors, GFP_NOIO, bounce_bio_split);
221		bio_chain(bio, *bio_orig);
222		generic_make_request(*bio_orig);
223		*bio_orig = bio;
224	}
225	bio = bio_clone_bioset(*bio_orig, GFP_NOIO, passthrough ? NULL :
226			bounce_bio_set);
227
228	bio_for_each_segment_all(to, bio, i) {
229		struct page *page = to->bv_page;
230
231		if (page_to_pfn(page) <= q->limits.bounce_pfn)
232			continue;
233
234		to->bv_page = mempool_alloc(pool, q->bounce_gfp);
235		inc_zone_page_state(to->bv_page, NR_BOUNCE);
236
237		if (rw == WRITE) {
238			char *vto, *vfrom;
239
240			flush_dcache_page(page);
241
242			vto = page_address(to->bv_page) + to->bv_offset;
243			vfrom = kmap_atomic(page) + to->bv_offset;
244			memcpy(vto, vfrom, to->bv_len);
245			kunmap_atomic(vfrom);
246		}
247	}
248
249	trace_block_bio_bounce(q, *bio_orig);
250
251	bio->bi_flags |= (1 << BIO_BOUNCED);
252
253	if (pool == page_pool) {
254		bio->bi_end_io = bounce_end_io_write;
255		if (rw == READ)
256			bio->bi_end_io = bounce_end_io_read;
257	} else {
258		bio->bi_end_io = bounce_end_io_write_isa;
259		if (rw == READ)
260			bio->bi_end_io = bounce_end_io_read_isa;
261	}
262
263	bio->bi_private = *bio_orig;
264	*bio_orig = bio;
265}
266
267void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
268{
269	mempool_t *pool;
270
271	/*
272	 * Data-less bio, nothing to bounce
273	 */
274	if (!bio_has_data(*bio_orig))
275		return;
276
277	/*
278	 * for non-isa bounce case, just check if the bounce pfn is equal
279	 * to or bigger than the highest pfn in the system -- in that case,
280	 * don't waste time iterating over bio segments
281	 */
282	if (!(q->bounce_gfp & GFP_DMA)) {
283		if (q->limits.bounce_pfn >= blk_max_pfn)
284			return;
285		pool = page_pool;
286	} else {
287		BUG_ON(!isa_page_pool);
288		pool = isa_page_pool;
289	}
290
291	/*
292	 * slow path
293	 */
294	__blk_queue_bounce(q, bio_orig, pool);
295}