linux/block/blk-map.c
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   1/*
   2 * Functions related to mapping data to requests
   3 */
   4#include <linux/kernel.h>
   5#include <linux/module.h>
   6#include <linux/bio.h>
   7#include <linux/blkdev.h>
   8#include <scsi/sg.h>            /* for struct sg_iovec */
   9
  10#include "blk.h"
  11
  12int blk_rq_append_bio(struct request_queue *q, struct request *rq,
  13                      struct bio *bio)
  14{
  15        if (!rq->bio)
  16                blk_rq_bio_prep(q, rq, bio);
  17        else if (!ll_back_merge_fn(q, rq, bio))
  18                return -EINVAL;
  19        else {
  20                rq->biotail->bi_next = bio;
  21                rq->biotail = bio;
  22
  23                rq->__data_len += bio->bi_size;
  24        }
  25        return 0;
  26}
  27
  28static int __blk_rq_unmap_user(struct bio *bio)
  29{
  30        int ret = 0;
  31
  32        if (bio) {
  33                if (bio_flagged(bio, BIO_USER_MAPPED))
  34                        bio_unmap_user(bio);
  35                else
  36                        ret = bio_uncopy_user(bio);
  37        }
  38
  39        return ret;
  40}
  41
  42static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
  43                             struct rq_map_data *map_data, void __user *ubuf,
  44                             unsigned int len, gfp_t gfp_mask)
  45{
  46        unsigned long uaddr;
  47        struct bio *bio, *orig_bio;
  48        int reading, ret;
  49
  50        reading = rq_data_dir(rq) == READ;
  51
  52        /*
  53         * if alignment requirement is satisfied, map in user pages for
  54         * direct dma. else, set up kernel bounce buffers
  55         */
  56        uaddr = (unsigned long) ubuf;
  57        if (blk_rq_aligned(q, uaddr, len) && !map_data)
  58                bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
  59        else
  60                bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);
  61
  62        if (IS_ERR(bio))
  63                return PTR_ERR(bio);
  64
  65        if (map_data && map_data->null_mapped)
  66                bio->bi_flags |= (1 << BIO_NULL_MAPPED);
  67
  68        orig_bio = bio;
  69        blk_queue_bounce(q, &bio);
  70
  71        /*
  72         * We link the bounce buffer in and could have to traverse it
  73         * later so we have to get a ref to prevent it from being freed
  74         */
  75        bio_get(bio);
  76
  77        ret = blk_rq_append_bio(q, rq, bio);
  78        if (!ret)
  79                return bio->bi_size;
  80
  81        /* if it was boucned we must call the end io function */
  82        bio_endio(bio, 0);
  83        __blk_rq_unmap_user(orig_bio);
  84        bio_put(bio);
  85        return ret;
  86}
  87
  88/**
  89 * blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  90 * @q:          request queue where request should be inserted
  91 * @rq:         request structure to fill
  92 * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  93 * @ubuf:       the user buffer
  94 * @len:        length of user data
  95 * @gfp_mask:   memory allocation flags
  96 *
  97 * Description:
  98 *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
  99 *    a kernel bounce buffer is used.
 100 *
 101 *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 102 *    still in process context.
 103 *
 104 *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 105 *    before being submitted to the device, as pages mapped may be out of
 106 *    reach. It's the callers responsibility to make sure this happens. The
 107 *    original bio must be passed back in to blk_rq_unmap_user() for proper
 108 *    unmapping.
 109 */
 110int blk_rq_map_user(struct request_queue *q, struct request *rq,
 111                    struct rq_map_data *map_data, void __user *ubuf,
 112                    unsigned long len, gfp_t gfp_mask)
 113{
 114        unsigned long bytes_read = 0;
 115        struct bio *bio = NULL;
 116        int ret;
 117
 118        if (len > (queue_max_hw_sectors(q) << 9))
 119                return -EINVAL;
 120        if (!len)
 121                return -EINVAL;
 122
 123        if (!ubuf && (!map_data || !map_data->null_mapped))
 124                return -EINVAL;
 125
 126        while (bytes_read != len) {
 127                unsigned long map_len, end, start;
 128
 129                map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 130                end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 131                                                                >> PAGE_SHIFT;
 132                start = (unsigned long)ubuf >> PAGE_SHIFT;
 133
 134                /*
 135                 * A bad offset could cause us to require BIO_MAX_PAGES + 1
 136                 * pages. If this happens we just lower the requested
 137                 * mapping len by a page so that we can fit
 138                 */
 139                if (end - start > BIO_MAX_PAGES)
 140                        map_len -= PAGE_SIZE;
 141
 142                ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
 143                                        gfp_mask);
 144                if (ret < 0)
 145                        goto unmap_rq;
 146                if (!bio)
 147                        bio = rq->bio;
 148                bytes_read += ret;
 149                ubuf += ret;
 150
 151                if (map_data)
 152                        map_data->offset += ret;
 153        }
 154
 155        if (!bio_flagged(bio, BIO_USER_MAPPED))
 156                rq->cmd_flags |= REQ_COPY_USER;
 157
 158        rq->buffer = NULL;
 159        return 0;
 160unmap_rq:
 161        blk_rq_unmap_user(bio);
 162        rq->bio = NULL;
 163        return ret;
 164}
 165EXPORT_SYMBOL(blk_rq_map_user);
 166
 167/**
 168 * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
 169 * @q:          request queue where request should be inserted
 170 * @rq:         request to map data to
 171 * @map_data:   pointer to the rq_map_data holding pages (if necessary)
 172 * @iov:        pointer to the iovec
 173 * @iov_count:  number of elements in the iovec
 174 * @len:        I/O byte count
 175 * @gfp_mask:   memory allocation flags
 176 *
 177 * Description:
 178 *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 179 *    a kernel bounce buffer is used.
 180 *
 181 *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 182 *    still in process context.
 183 *
 184 *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 185 *    before being submitted to the device, as pages mapped may be out of
 186 *    reach. It's the callers responsibility to make sure this happens. The
 187 *    original bio must be passed back in to blk_rq_unmap_user() for proper
 188 *    unmapping.
 189 */
 190int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 191                        struct rq_map_data *map_data, struct sg_iovec *iov,
 192                        int iov_count, unsigned int len, gfp_t gfp_mask)
 193{
 194        struct bio *bio;
 195        int i, read = rq_data_dir(rq) == READ;
 196        int unaligned = 0;
 197
 198        if (!iov || iov_count <= 0)
 199                return -EINVAL;
 200
 201        for (i = 0; i < iov_count; i++) {
 202                unsigned long uaddr = (unsigned long)iov[i].iov_base;
 203
 204                if (!iov[i].iov_len)
 205                        return -EINVAL;
 206
 207                /*
 208                 * Keep going so we check length of all segments
 209                 */
 210                if (uaddr & queue_dma_alignment(q))
 211                        unaligned = 1;
 212        }
 213
 214        if (unaligned || (q->dma_pad_mask & len) || map_data)
 215                bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
 216                                        gfp_mask);
 217        else
 218                bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
 219
 220        if (IS_ERR(bio))
 221                return PTR_ERR(bio);
 222
 223        if (bio->bi_size != len) {
 224                /*
 225                 * Grab an extra reference to this bio, as bio_unmap_user()
 226                 * expects to be able to drop it twice as it happens on the
 227                 * normal IO completion path
 228                 */
 229                bio_get(bio);
 230                bio_endio(bio, 0);
 231                __blk_rq_unmap_user(bio);
 232                return -EINVAL;
 233        }
 234
 235        if (!bio_flagged(bio, BIO_USER_MAPPED))
 236                rq->cmd_flags |= REQ_COPY_USER;
 237
 238        blk_queue_bounce(q, &bio);
 239        bio_get(bio);
 240        blk_rq_bio_prep(q, rq, bio);
 241        rq->buffer = NULL;
 242        return 0;
 243}
 244EXPORT_SYMBOL(blk_rq_map_user_iov);
 245
 246/**
 247 * blk_rq_unmap_user - unmap a request with user data
 248 * @bio:               start of bio list
 249 *
 250 * Description:
 251 *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 252 *    supply the original rq->bio from the blk_rq_map_user() return, since
 253 *    the I/O completion may have changed rq->bio.
 254 */
 255int blk_rq_unmap_user(struct bio *bio)
 256{
 257        struct bio *mapped_bio;
 258        int ret = 0, ret2;
 259
 260        while (bio) {
 261                mapped_bio = bio;
 262                if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 263                        mapped_bio = bio->bi_private;
 264
 265                ret2 = __blk_rq_unmap_user(mapped_bio);
 266                if (ret2 && !ret)
 267                        ret = ret2;
 268
 269                mapped_bio = bio;
 270                bio = bio->bi_next;
 271                bio_put(mapped_bio);
 272        }
 273
 274        return ret;
 275}
 276EXPORT_SYMBOL(blk_rq_unmap_user);
 277
 278/**
 279 * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 280 * @q:          request queue where request should be inserted
 281 * @rq:         request to fill
 282 * @kbuf:       the kernel buffer
 283 * @len:        length of user data
 284 * @gfp_mask:   memory allocation flags
 285 *
 286 * Description:
 287 *    Data will be mapped directly if possible. Otherwise a bounce
 288 *    buffer is used. Can be called multple times to append multple
 289 *    buffers.
 290 */
 291int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 292                    unsigned int len, gfp_t gfp_mask)
 293{
 294        int reading = rq_data_dir(rq) == READ;
 295        unsigned long addr = (unsigned long) kbuf;
 296        int do_copy = 0;
 297        struct bio *bio;
 298        int ret;
 299
 300        if (len > (queue_max_hw_sectors(q) << 9))
 301                return -EINVAL;
 302        if (!len || !kbuf)
 303                return -EINVAL;
 304
 305        do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 306        if (do_copy)
 307                bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 308        else
 309                bio = bio_map_kern(q, kbuf, len, gfp_mask);
 310
 311        if (IS_ERR(bio))
 312                return PTR_ERR(bio);
 313
 314        if (!reading)
 315                bio->bi_rw |= REQ_WRITE;
 316
 317        if (do_copy)
 318                rq->cmd_flags |= REQ_COPY_USER;
 319
 320        ret = blk_rq_append_bio(q, rq, bio);
 321        if (unlikely(ret)) {
 322                /* request is too big */
 323                bio_put(bio);
 324                return ret;
 325        }
 326
 327        blk_queue_bounce(q, &rq->bio);
 328        rq->buffer = NULL;
 329        return 0;
 330}
 331EXPORT_SYMBOL(blk_rq_map_kern);
 332
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