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

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