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Linux/block/bounce.c

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

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