Root/drivers/md/dm-io.c

1/*
2 * Copyright (C) 2003 Sistina Software
3 * Copyright (C) 2006 Red Hat GmbH
4 *
5 * This file is released under the GPL.
6 */
7
8#include "dm.h"
9
10#include <linux/device-mapper.h>
11
12#include <linux/bio.h>
13#include <linux/mempool.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/slab.h>
17#include <linux/dm-io.h>
18
19#define DM_MSG_PREFIX "io"
20
21#define DM_IO_MAX_REGIONS BITS_PER_LONG
22#define MIN_IOS 16
23#define MIN_BIOS 16
24
25struct dm_io_client {
26    mempool_t *pool;
27    struct bio_set *bios;
28};
29
30/*
31 * Aligning 'struct io' reduces the number of bits required to store
32 * its address. Refer to store_io_and_region_in_bio() below.
33 */
34struct io {
35    unsigned long error_bits;
36    atomic_t count;
37    struct task_struct *sleeper;
38    struct dm_io_client *client;
39    io_notify_fn callback;
40    void *context;
41    void *vma_invalidate_address;
42    unsigned long vma_invalidate_size;
43} __attribute__((aligned(DM_IO_MAX_REGIONS)));
44
45static struct kmem_cache *_dm_io_cache;
46
47/*
48 * Create a client with mempool and bioset.
49 */
50struct dm_io_client *dm_io_client_create(void)
51{
52    struct dm_io_client *client;
53
54    client = kmalloc(sizeof(*client), GFP_KERNEL);
55    if (!client)
56        return ERR_PTR(-ENOMEM);
57
58    client->pool = mempool_create_slab_pool(MIN_IOS, _dm_io_cache);
59    if (!client->pool)
60        goto bad;
61
62    client->bios = bioset_create(MIN_BIOS, 0);
63    if (!client->bios)
64        goto bad;
65
66    return client;
67
68   bad:
69    if (client->pool)
70        mempool_destroy(client->pool);
71    kfree(client);
72    return ERR_PTR(-ENOMEM);
73}
74EXPORT_SYMBOL(dm_io_client_create);
75
76void dm_io_client_destroy(struct dm_io_client *client)
77{
78    mempool_destroy(client->pool);
79    bioset_free(client->bios);
80    kfree(client);
81}
82EXPORT_SYMBOL(dm_io_client_destroy);
83
84/*-----------------------------------------------------------------
85 * We need to keep track of which region a bio is doing io for.
86 * To avoid a memory allocation to store just 5 or 6 bits, we
87 * ensure the 'struct io' pointer is aligned so enough low bits are
88 * always zero and then combine it with the region number directly in
89 * bi_private.
90 *---------------------------------------------------------------*/
91static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
92                       unsigned region)
93{
94    if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
95        DMCRIT("Unaligned struct io pointer %p", io);
96        BUG();
97    }
98
99    bio->bi_private = (void *)((unsigned long)io | region);
100}
101
102static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
103                       unsigned *region)
104{
105    unsigned long val = (unsigned long)bio->bi_private;
106
107    *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
108    *region = val & (DM_IO_MAX_REGIONS - 1);
109}
110
111/*-----------------------------------------------------------------
112 * We need an io object to keep track of the number of bios that
113 * have been dispatched for a particular io.
114 *---------------------------------------------------------------*/
115static void dec_count(struct io *io, unsigned int region, int error)
116{
117    if (error)
118        set_bit(region, &io->error_bits);
119
120    if (atomic_dec_and_test(&io->count)) {
121        if (io->vma_invalidate_size)
122            invalidate_kernel_vmap_range(io->vma_invalidate_address,
123                             io->vma_invalidate_size);
124
125        if (io->sleeper)
126            wake_up_process(io->sleeper);
127
128        else {
129            unsigned long r = io->error_bits;
130            io_notify_fn fn = io->callback;
131            void *context = io->context;
132
133            mempool_free(io, io->client->pool);
134            fn(r, context);
135        }
136    }
137}
138
139static void endio(struct bio *bio, int error)
140{
141    struct io *io;
142    unsigned region;
143
144    if (error && bio_data_dir(bio) == READ)
145        zero_fill_bio(bio);
146
147    /*
148     * The bio destructor in bio_put() may use the io object.
149     */
150    retrieve_io_and_region_from_bio(bio, &io, &region);
151
152    bio_put(bio);
153
154    dec_count(io, region, error);
155}
156
157/*-----------------------------------------------------------------
158 * These little objects provide an abstraction for getting a new
159 * destination page for io.
160 *---------------------------------------------------------------*/
161struct dpages {
162    void (*get_page)(struct dpages *dp,
163             struct page **p, unsigned long *len, unsigned *offset);
164    void (*next_page)(struct dpages *dp);
165
166    unsigned context_u;
167    void *context_ptr;
168
169    void *vma_invalidate_address;
170    unsigned long vma_invalidate_size;
171};
172
173/*
174 * Functions for getting the pages from a list.
175 */
176static void list_get_page(struct dpages *dp,
177          struct page **p, unsigned long *len, unsigned *offset)
178{
179    unsigned o = dp->context_u;
180    struct page_list *pl = (struct page_list *) dp->context_ptr;
181
182    *p = pl->page;
183    *len = PAGE_SIZE - o;
184    *offset = o;
185}
186
187static void list_next_page(struct dpages *dp)
188{
189    struct page_list *pl = (struct page_list *) dp->context_ptr;
190    dp->context_ptr = pl->next;
191    dp->context_u = 0;
192}
193
194static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
195{
196    dp->get_page = list_get_page;
197    dp->next_page = list_next_page;
198    dp->context_u = offset;
199    dp->context_ptr = pl;
200}
201
202/*
203 * Functions for getting the pages from a bvec.
204 */
205static void bvec_get_page(struct dpages *dp,
206          struct page **p, unsigned long *len, unsigned *offset)
207{
208    struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
209    *p = bvec->bv_page;
210    *len = bvec->bv_len;
211    *offset = bvec->bv_offset;
212}
213
214static void bvec_next_page(struct dpages *dp)
215{
216    struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
217    dp->context_ptr = bvec + 1;
218}
219
220static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
221{
222    dp->get_page = bvec_get_page;
223    dp->next_page = bvec_next_page;
224    dp->context_ptr = bvec;
225}
226
227/*
228 * Functions for getting the pages from a VMA.
229 */
230static void vm_get_page(struct dpages *dp,
231         struct page **p, unsigned long *len, unsigned *offset)
232{
233    *p = vmalloc_to_page(dp->context_ptr);
234    *offset = dp->context_u;
235    *len = PAGE_SIZE - dp->context_u;
236}
237
238static void vm_next_page(struct dpages *dp)
239{
240    dp->context_ptr += PAGE_SIZE - dp->context_u;
241    dp->context_u = 0;
242}
243
244static void vm_dp_init(struct dpages *dp, void *data)
245{
246    dp->get_page = vm_get_page;
247    dp->next_page = vm_next_page;
248    dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
249    dp->context_ptr = data;
250}
251
252static void dm_bio_destructor(struct bio *bio)
253{
254    unsigned region;
255    struct io *io;
256
257    retrieve_io_and_region_from_bio(bio, &io, &region);
258
259    bio_free(bio, io->client->bios);
260}
261
262/*
263 * Functions for getting the pages from kernel memory.
264 */
265static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
266            unsigned *offset)
267{
268    *p = virt_to_page(dp->context_ptr);
269    *offset = dp->context_u;
270    *len = PAGE_SIZE - dp->context_u;
271}
272
273static void km_next_page(struct dpages *dp)
274{
275    dp->context_ptr += PAGE_SIZE - dp->context_u;
276    dp->context_u = 0;
277}
278
279static void km_dp_init(struct dpages *dp, void *data)
280{
281    dp->get_page = km_get_page;
282    dp->next_page = km_next_page;
283    dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
284    dp->context_ptr = data;
285}
286
287/*-----------------------------------------------------------------
288 * IO routines that accept a list of pages.
289 *---------------------------------------------------------------*/
290static void do_region(int rw, unsigned region, struct dm_io_region *where,
291              struct dpages *dp, struct io *io)
292{
293    struct bio *bio;
294    struct page *page;
295    unsigned long len;
296    unsigned offset;
297    unsigned num_bvecs;
298    sector_t remaining = where->count;
299    struct request_queue *q = bdev_get_queue(where->bdev);
300    sector_t discard_sectors;
301
302    /*
303     * where->count may be zero if rw holds a flush and we need to
304     * send a zero-sized flush.
305     */
306    do {
307        /*
308         * Allocate a suitably sized-bio.
309         */
310        if (rw & REQ_DISCARD)
311            num_bvecs = 1;
312        else
313            num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
314                      dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
315
316        bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
317        bio->bi_sector = where->sector + (where->count - remaining);
318        bio->bi_bdev = where->bdev;
319        bio->bi_end_io = endio;
320        bio->bi_destructor = dm_bio_destructor;
321        store_io_and_region_in_bio(bio, io, region);
322
323        if (rw & REQ_DISCARD) {
324            discard_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
325            bio->bi_size = discard_sectors << SECTOR_SHIFT;
326            remaining -= discard_sectors;
327        } else while (remaining) {
328            /*
329             * Try and add as many pages as possible.
330             */
331            dp->get_page(dp, &page, &len, &offset);
332            len = min(len, to_bytes(remaining));
333            if (!bio_add_page(bio, page, len, offset))
334                break;
335
336            offset = 0;
337            remaining -= to_sector(len);
338            dp->next_page(dp);
339        }
340
341        atomic_inc(&io->count);
342        submit_bio(rw, bio);
343    } while (remaining);
344}
345
346static void dispatch_io(int rw, unsigned int num_regions,
347            struct dm_io_region *where, struct dpages *dp,
348            struct io *io, int sync)
349{
350    int i;
351    struct dpages old_pages = *dp;
352
353    BUG_ON(num_regions > DM_IO_MAX_REGIONS);
354
355    if (sync)
356        rw |= REQ_SYNC;
357
358    /*
359     * For multiple regions we need to be careful to rewind
360     * the dp object for each call to do_region.
361     */
362    for (i = 0; i < num_regions; i++) {
363        *dp = old_pages;
364        if (where[i].count || (rw & REQ_FLUSH))
365            do_region(rw, i, where + i, dp, io);
366    }
367
368    /*
369     * Drop the extra reference that we were holding to avoid
370     * the io being completed too early.
371     */
372    dec_count(io, 0, 0);
373}
374
375static int sync_io(struct dm_io_client *client, unsigned int num_regions,
376           struct dm_io_region *where, int rw, struct dpages *dp,
377           unsigned long *error_bits)
378{
379    /*
380     * gcc <= 4.3 can't do the alignment for stack variables, so we must
381     * align it on our own.
382     * volatile prevents the optimizer from removing or reusing
383     * "io_" field from the stack frame (allowed in ANSI C).
384     */
385    volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
386    struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
387
388    if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
389        WARN_ON(1);
390        return -EIO;
391    }
392
393    io->error_bits = 0;
394    atomic_set(&io->count, 1); /* see dispatch_io() */
395    io->sleeper = current;
396    io->client = client;
397
398    io->vma_invalidate_address = dp->vma_invalidate_address;
399    io->vma_invalidate_size = dp->vma_invalidate_size;
400
401    dispatch_io(rw, num_regions, where, dp, io, 1);
402
403    while (1) {
404        set_current_state(TASK_UNINTERRUPTIBLE);
405
406        if (!atomic_read(&io->count))
407            break;
408
409        io_schedule();
410    }
411    set_current_state(TASK_RUNNING);
412
413    if (error_bits)
414        *error_bits = io->error_bits;
415
416    return io->error_bits ? -EIO : 0;
417}
418
419static int async_io(struct dm_io_client *client, unsigned int num_regions,
420            struct dm_io_region *where, int rw, struct dpages *dp,
421            io_notify_fn fn, void *context)
422{
423    struct io *io;
424
425    if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
426        WARN_ON(1);
427        fn(1, context);
428        return -EIO;
429    }
430
431    io = mempool_alloc(client->pool, GFP_NOIO);
432    io->error_bits = 0;
433    atomic_set(&io->count, 1); /* see dispatch_io() */
434    io->sleeper = NULL;
435    io->client = client;
436    io->callback = fn;
437    io->context = context;
438
439    io->vma_invalidate_address = dp->vma_invalidate_address;
440    io->vma_invalidate_size = dp->vma_invalidate_size;
441
442    dispatch_io(rw, num_regions, where, dp, io, 0);
443    return 0;
444}
445
446static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
447           unsigned long size)
448{
449    /* Set up dpages based on memory type */
450
451    dp->vma_invalidate_address = NULL;
452    dp->vma_invalidate_size = 0;
453
454    switch (io_req->mem.type) {
455    case DM_IO_PAGE_LIST:
456        list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
457        break;
458
459    case DM_IO_BVEC:
460        bvec_dp_init(dp, io_req->mem.ptr.bvec);
461        break;
462
463    case DM_IO_VMA:
464        flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
465        if ((io_req->bi_rw & RW_MASK) == READ) {
466            dp->vma_invalidate_address = io_req->mem.ptr.vma;
467            dp->vma_invalidate_size = size;
468        }
469        vm_dp_init(dp, io_req->mem.ptr.vma);
470        break;
471
472    case DM_IO_KMEM:
473        km_dp_init(dp, io_req->mem.ptr.addr);
474        break;
475
476    default:
477        return -EINVAL;
478    }
479
480    return 0;
481}
482
483/*
484 * New collapsed (a)synchronous interface.
485 *
486 * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
487 * the queue with blk_unplug() some time later or set REQ_SYNC in
488io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
489 * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
490 */
491int dm_io(struct dm_io_request *io_req, unsigned num_regions,
492      struct dm_io_region *where, unsigned long *sync_error_bits)
493{
494    int r;
495    struct dpages dp;
496
497    r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
498    if (r)
499        return r;
500
501    if (!io_req->notify.fn)
502        return sync_io(io_req->client, num_regions, where,
503                   io_req->bi_rw, &dp, sync_error_bits);
504
505    return async_io(io_req->client, num_regions, where, io_req->bi_rw,
506            &dp, io_req->notify.fn, io_req->notify.context);
507}
508EXPORT_SYMBOL(dm_io);
509
510int __init dm_io_init(void)
511{
512    _dm_io_cache = KMEM_CACHE(io, 0);
513    if (!_dm_io_cache)
514        return -ENOMEM;
515
516    return 0;
517}
518
519void dm_io_exit(void)
520{
521    kmem_cache_destroy(_dm_io_cache);
522    _dm_io_cache = NULL;
523}
524

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