Root/mm/bounce.c

1/* bounce buffer handling for block devices
2 *
3 * - Split from highmem.c
4 */
5
6#include <linux/mm.h>
7#include <linux/module.h>
8#include <linux/swap.h>
9#include <linux/gfp.h>
10#include <linux/bio.h>
11#include <linux/pagemap.h>
12#include <linux/mempool.h>
13#include <linux/blkdev.h>
14#include <linux/init.h>
15#include <linux/hash.h>
16#include <linux/highmem.h>
17#include <asm/tlbflush.h>
18
19#include <trace/events/block.h>
20
21#define POOL_SIZE 64
22#define ISA_POOL_SIZE 16
23
24static mempool_t *page_pool, *isa_page_pool;
25
26#ifdef CONFIG_HIGHMEM
27static __init int init_emergency_pool(void)
28{
29    struct sysinfo i;
30    si_meminfo(&i);
31    si_swapinfo(&i);
32
33    if (!i.totalhigh)
34        return 0;
35
36    page_pool = mempool_create_page_pool(POOL_SIZE, 0);
37    BUG_ON(!page_pool);
38    printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
39
40    return 0;
41}
42
43__initcall(init_emergency_pool);
44
45/*
46 * highmem version, map in to vec
47 */
48static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
49{
50    unsigned long flags;
51    unsigned char *vto;
52
53    local_irq_save(flags);
54    vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
55    memcpy(vto + to->bv_offset, vfrom, to->bv_len);
56    kunmap_atomic(vto, KM_BOUNCE_READ);
57    local_irq_restore(flags);
58}
59
60#else /* CONFIG_HIGHMEM */
61
62#define bounce_copy_vec(to, vfrom) \
63    memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
64
65#endif /* CONFIG_HIGHMEM */
66
67/*
68 * allocate pages in the DMA region for the ISA pool
69 */
70static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
71{
72    return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
73}
74
75/*
76 * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
77 * as the max address, so check if the pool has already been created.
78 */
79int init_emergency_isa_pool(void)
80{
81    if (isa_page_pool)
82        return 0;
83
84    isa_page_pool = mempool_create(ISA_POOL_SIZE, mempool_alloc_pages_isa,
85                       mempool_free_pages, (void *) 0);
86    BUG_ON(!isa_page_pool);
87
88    printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
89    return 0;
90}
91
92/*
93 * Simple bounce buffer support for highmem pages. Depending on the
94 * queue gfp mask set, *to may or may not be a highmem page. kmap it
95 * always, it will do the Right Thing
96 */
97static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
98{
99    unsigned char *vfrom;
100    struct bio_vec *tovec, *fromvec;
101    int i;
102
103    __bio_for_each_segment(tovec, to, i, 0) {
104        fromvec = from->bi_io_vec + i;
105
106        /*
107         * not bounced
108         */
109        if (tovec->bv_page == fromvec->bv_page)
110            continue;
111
112        /*
113         * fromvec->bv_offset and fromvec->bv_len might have been
114         * modified by the block layer, so use the original copy,
115         * bounce_copy_vec already uses tovec->bv_len
116         */
117        vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
118
119        bounce_copy_vec(tovec, vfrom);
120        flush_dcache_page(tovec->bv_page);
121    }
122}
123
124static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
125{
126    struct bio *bio_orig = bio->bi_private;
127    struct bio_vec *bvec, *org_vec;
128    int i;
129
130    if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
131        set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);
132
133    /*
134     * free up bounce indirect pages used
135     */
136    __bio_for_each_segment(bvec, bio, i, 0) {
137        org_vec = bio_orig->bi_io_vec + i;
138        if (bvec->bv_page == org_vec->bv_page)
139            continue;
140
141        dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
142        mempool_free(bvec->bv_page, pool);
143    }
144
145    bio_endio(bio_orig, err);
146    bio_put(bio);
147}
148
149static void bounce_end_io_write(struct bio *bio, int err)
150{
151    bounce_end_io(bio, page_pool, err);
152}
153
154static void bounce_end_io_write_isa(struct bio *bio, int err)
155{
156
157    bounce_end_io(bio, isa_page_pool, err);
158}
159
160static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
161{
162    struct bio *bio_orig = bio->bi_private;
163
164    if (test_bit(BIO_UPTODATE, &bio->bi_flags))
165        copy_to_high_bio_irq(bio_orig, bio);
166
167    bounce_end_io(bio, pool, err);
168}
169
170static void bounce_end_io_read(struct bio *bio, int err)
171{
172    __bounce_end_io_read(bio, page_pool, err);
173}
174
175static void bounce_end_io_read_isa(struct bio *bio, int err)
176{
177    __bounce_end_io_read(bio, isa_page_pool, err);
178}
179
180static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
181                   mempool_t *pool)
182{
183    struct page *page;
184    struct bio *bio = NULL;
185    int i, rw = bio_data_dir(*bio_orig);
186    struct bio_vec *to, *from;
187
188    bio_for_each_segment(from, *bio_orig, i) {
189        page = from->bv_page;
190
191        /*
192         * is destination page below bounce pfn?
193         */
194        if (page_to_pfn(page) <= queue_bounce_pfn(q))
195            continue;
196
197        /*
198         * irk, bounce it
199         */
200        if (!bio) {
201            unsigned int cnt = (*bio_orig)->bi_vcnt;
202
203            bio = bio_alloc(GFP_NOIO, cnt);
204            memset(bio->bi_io_vec, 0, cnt * sizeof(struct bio_vec));
205        }
206            
207
208        to = bio->bi_io_vec + i;
209
210        to->bv_page = mempool_alloc(pool, q->bounce_gfp);
211        to->bv_len = from->bv_len;
212        to->bv_offset = from->bv_offset;
213        inc_zone_page_state(to->bv_page, NR_BOUNCE);
214
215        if (rw == WRITE) {
216            char *vto, *vfrom;
217
218            flush_dcache_page(from->bv_page);
219            vto = page_address(to->bv_page) + to->bv_offset;
220            vfrom = kmap(from->bv_page) + from->bv_offset;
221            memcpy(vto, vfrom, to->bv_len);
222            kunmap(from->bv_page);
223        }
224    }
225
226    /*
227     * no pages bounced
228     */
229    if (!bio)
230        return;
231
232    trace_block_bio_bounce(q, *bio_orig);
233
234    /*
235     * at least one page was bounced, fill in possible non-highmem
236     * pages
237     */
238    __bio_for_each_segment(from, *bio_orig, i, 0) {
239        to = bio_iovec_idx(bio, i);
240        if (!to->bv_page) {
241            to->bv_page = from->bv_page;
242            to->bv_len = from->bv_len;
243            to->bv_offset = from->bv_offset;
244        }
245    }
246
247    bio->bi_bdev = (*bio_orig)->bi_bdev;
248    bio->bi_flags |= (1 << BIO_BOUNCED);
249    bio->bi_sector = (*bio_orig)->bi_sector;
250    bio->bi_rw = (*bio_orig)->bi_rw;
251
252    bio->bi_vcnt = (*bio_orig)->bi_vcnt;
253    bio->bi_idx = (*bio_orig)->bi_idx;
254    bio->bi_size = (*bio_orig)->bi_size;
255
256    if (pool == page_pool) {
257        bio->bi_end_io = bounce_end_io_write;
258        if (rw == READ)
259            bio->bi_end_io = bounce_end_io_read;
260    } else {
261        bio->bi_end_io = bounce_end_io_write_isa;
262        if (rw == READ)
263            bio->bi_end_io = bounce_end_io_read_isa;
264    }
265
266    bio->bi_private = *bio_orig;
267    *bio_orig = bio;
268}
269
270void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
271{
272    mempool_t *pool;
273
274    /*
275     * Data-less bio, nothing to bounce
276     */
277    if (!bio_has_data(*bio_orig))
278        return;
279
280    /*
281     * for non-isa bounce case, just check if the bounce pfn is equal
282     * to or bigger than the highest pfn in the system -- in that case,
283     * don't waste time iterating over bio segments
284     */
285    if (!(q->bounce_gfp & GFP_DMA)) {
286        if (queue_bounce_pfn(q) >= blk_max_pfn)
287            return;
288        pool = page_pool;
289    } else {
290        BUG_ON(!isa_page_pool);
291        pool = isa_page_pool;
292    }
293
294    /*
295     * slow path
296     */
297    __blk_queue_bounce(q, bio_orig, pool);
298}
299
300EXPORT_SYMBOL(blk_queue_bounce);
301

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