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}
  27EXPORT_SYMBOL(blk_rq_append_bio);
  28
  29static int __blk_rq_unmap_user(struct bio *bio)
  30{
  31        int ret = 0;
  32
  33        if (bio) {
  34                if (bio_flagged(bio, BIO_USER_MAPPED))
  35                        bio_unmap_user(bio);
  36                else
  37                        ret = bio_uncopy_user(bio);
  38        }
  39
  40        return ret;
  41}
  42
  43static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
  44                             struct rq_map_data *map_data, void __user *ubuf,
  45                             unsigned int len, int null_mapped, gfp_t gfp_mask)
  46{
  47        unsigned long uaddr;
  48        struct bio *bio, *orig_bio;
  49        int reading, ret;
  50
  51        reading = rq_data_dir(rq) == READ;
  52
  53        /*
  54         * if alignment requirement is satisfied, map in user pages for
  55         * direct dma. else, set up kernel bounce buffers
  56         */
  57        uaddr = (unsigned long) ubuf;
  58        if (blk_rq_aligned(q, ubuf, len) && !map_data)
  59                bio = bio_map_user(q, NULL, uaddr, len, reading, gfp_mask);
  60        else
  61                bio = bio_copy_user(q, map_data, uaddr, len, reading, gfp_mask);
  62
  63        if (IS_ERR(bio))
  64                return PTR_ERR(bio);
  65
  66        if (null_mapped)
  67                bio->bi_flags |= (1 << BIO_NULL_MAPPED);
  68
  69        orig_bio = bio;
  70        blk_queue_bounce(q, &bio);
  71
  72        /*
  73         * We link the bounce buffer in and could have to traverse it
  74         * later so we have to get a ref to prevent it from being freed
  75         */
  76        bio_get(bio);
  77
  78        ret = blk_rq_append_bio(q, rq, bio);
  79        if (!ret)
  80                return bio->bi_size;
  81
  82        /* if it was boucned we must call the end io function */
  83        bio_endio(bio, 0);
  84        __blk_rq_unmap_user(orig_bio);
  85        bio_put(bio);
  86        return ret;
  87}
  88
  89/**
  90 * blk_rq_map_user - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  91 * @q:          request queue where request should be inserted
  92 * @rq:         request structure to fill
  93 * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  94 * @ubuf:       the user buffer
  95 * @len:        length of user data
  96 * @gfp_mask:   memory allocation flags
  97 *
  98 * Description:
  99 *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 100 *    a kernel bounce buffer is used.
 101 *
 102 *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 103 *    still in process context.
 104 *
 105 *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 106 *    before being submitted to the device, as pages mapped may be out of
 107 *    reach. It's the callers responsibility to make sure this happens. The
 108 *    original bio must be passed back in to blk_rq_unmap_user() for proper
 109 *    unmapping.
 110 */
 111int blk_rq_map_user(struct request_queue *q, struct request *rq,
 112                    struct rq_map_data *map_data, void __user *ubuf,
 113                    unsigned long len, gfp_t gfp_mask)
 114{
 115        unsigned long bytes_read = 0;
 116        struct bio *bio = NULL;
 117        int ret, null_mapped = 0;
 118
 119        if (len > (q->max_hw_sectors << 9))
 120                return -EINVAL;
 121        if (!len)
 122                return -EINVAL;
 123        if (!ubuf) {
 124                if (!map_data || rq_data_dir(rq) != READ)
 125                        return -EINVAL;
 126                null_mapped = 1;
 127        }
 128
 129        while (bytes_read != len) {
 130                unsigned long map_len, end, start;
 131
 132                map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 133                end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 134                                                                >> PAGE_SHIFT;
 135                start = (unsigned long)ubuf >> PAGE_SHIFT;
 136
 137                /*
 138                 * A bad offset could cause us to require BIO_MAX_PAGES + 1
 139                 * pages. If this happens we just lower the requested
 140                 * mapping len by a page so that we can fit
 141                 */
 142                if (end - start > BIO_MAX_PAGES)
 143                        map_len -= PAGE_SIZE;
 144
 145                ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
 146                                        null_mapped, gfp_mask);
 147                if (ret < 0)
 148                        goto unmap_rq;
 149                if (!bio)
 150                        bio = rq->bio;
 151                bytes_read += ret;
 152                ubuf += ret;
 153        }
 154
 155        if (!bio_flagged(bio, BIO_USER_MAPPED))
 156                rq->cmd_flags |= REQ_COPY_USER;
 157
 158        rq->buffer = rq->data = 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 (uaddr & queue_dma_alignment(q)) {
 205                        unaligned = 1;
 206                        break;
 207                }
 208        }
 209
 210        if (unaligned || (q->dma_pad_mask & len) || map_data)
 211                bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
 212                                        gfp_mask);
 213        else
 214                bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
 215
 216        if (IS_ERR(bio))
 217                return PTR_ERR(bio);
 218
 219        if (bio->bi_size != len) {
 220                /*
 221                 * Grab an extra reference to this bio, as bio_unmap_user()
 222                 * expects to be able to drop it twice as it happens on the
 223                 * normal IO completion path
 224                 */
 225                bio_get(bio);
 226                bio_endio(bio, 0);
 227                __blk_rq_unmap_user(bio);
 228                return -EINVAL;
 229        }
 230
 231        if (!bio_flagged(bio, BIO_USER_MAPPED))
 232                rq->cmd_flags |= REQ_COPY_USER;
 233
 234        blk_queue_bounce(q, &bio);
 235        bio_get(bio);
 236        blk_rq_bio_prep(q, rq, bio);
 237        rq->buffer = rq->data = NULL;
 238        return 0;
 239}
 240EXPORT_SYMBOL(blk_rq_map_user_iov);
 241
 242/**
 243 * blk_rq_unmap_user - unmap a request with user data
 244 * @bio:               start of bio list
 245 *
 246 * Description:
 247 *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 248 *    supply the original rq->bio from the blk_rq_map_user() return, since
 249 *    the I/O completion may have changed rq->bio.
 250 */
 251int blk_rq_unmap_user(struct bio *bio)
 252{
 253        struct bio *mapped_bio;
 254        int ret = 0, ret2;
 255
 256        while (bio) {
 257                mapped_bio = bio;
 258                if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 259                        mapped_bio = bio->bi_private;
 260
 261                ret2 = __blk_rq_unmap_user(mapped_bio);
 262                if (ret2 && !ret)
 263                        ret = ret2;
 264
 265                mapped_bio = bio;
 266                bio = bio->bi_next;
 267                bio_put(mapped_bio);
 268        }
 269
 270        return ret;
 271}
 272EXPORT_SYMBOL(blk_rq_unmap_user);
 273
 274/**
 275 * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 276 * @q:          request queue where request should be inserted
 277 * @rq:         request to fill
 278 * @kbuf:       the kernel buffer
 279 * @len:        length of user data
 280 * @gfp_mask:   memory allocation flags
 281 *
 282 * Description:
 283 *    Data will be mapped directly if possible. Otherwise a bounce
 284 *    buffer is used.
 285 */
 286int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 287                    unsigned int len, gfp_t gfp_mask)
 288{
 289        int reading = rq_data_dir(rq) == READ;
 290        int do_copy = 0;
 291        struct bio *bio;
 292
 293        if (len > (q->max_hw_sectors << 9))
 294                return -EINVAL;
 295        if (!len || !kbuf)
 296                return -EINVAL;
 297
 298        do_copy = !blk_rq_aligned(q, kbuf, len) || object_is_on_stack(kbuf);
 299        if (do_copy)
 300                bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 301        else
 302                bio = bio_map_kern(q, kbuf, len, gfp_mask);
 303
 304        if (IS_ERR(bio))
 305                return PTR_ERR(bio);
 306
 307        if (rq_data_dir(rq) == WRITE)
 308                bio->bi_rw |= (1 << BIO_RW);
 309
 310        if (do_copy)
 311                rq->cmd_flags |= REQ_COPY_USER;
 312
 313        blk_rq_bio_prep(q, rq, bio);
 314        blk_queue_bounce(q, &rq->bio);
 315        rq->buffer = rq->data = NULL;
 316        return 0;
 317}
 318EXPORT_SYMBOL(blk_rq_map_kern);
 319
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