block/blk-map.c

   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
  12 int 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
  28 static 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
  42 static 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, ubuf, 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  */
 110 int 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;
 160 unmap_rq:
 161         blk_rq_unmap_user(bio);
 162         rq->bio = NULL;
 163         return ret;
 164 }
 165 EXPORT_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  */
 190 int 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 = NULL;
 238         return 0;
 239 }
 240 EXPORT_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  */
 251 int 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 }
 272 EXPORT_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. Can be called multple times to append multple
 285  *    buffers.
 286  */
 287 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 288                     unsigned int len, gfp_t gfp_mask)
 289 {
 290         int reading = rq_data_dir(rq) == READ;
 291         int do_copy = 0;
 292         struct bio *bio;
 293         int ret;
 294
 295         if (len > (queue_max_hw_sectors(q) << 9))
 296                 return -EINVAL;
 297         if (!len || !kbuf)
 298                 return -EINVAL;
 299
 300         do_copy = !blk_rq_aligned(q, kbuf, len) || object_is_on_stack(kbuf);
 301         if (do_copy)
 302                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 303         else
 304                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 305
 306         if (IS_ERR(bio))
 307                 return PTR_ERR(bio);
 308
 309         if (rq_data_dir(rq) == WRITE)
 310                 bio->bi_rw |= (1 << BIO_RW);
 311
 312         if (do_copy)
 313                 rq->cmd_flags |= REQ_COPY_USER;
 314
 315         ret = blk_rq_append_bio(q, rq, bio);
 316         if (unlikely(ret)) {
 317                 /* request is too big */
 318                 bio_put(bio);
 319                 return ret;
 320         }
 321
 322         blk_queue_bounce(q, &rq->bio);
 323         rq->buffer = NULL;
 324         return 0;
 325 }
 326 EXPORT_SYMBOL(blk_rq_map_kern);