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 EXPORT_SYMBOL(blk_rq_append_bio);
  28
  29 static 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
  43 static 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, 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 (map_data && map_data->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  */
 111 int 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;
 118
 119         if (len > (q->max_hw_sectors << 9))
 120                 return -EINVAL;
 121         if (!len)
 122                 return -EINVAL;
 123
 124         if (!ubuf && (!map_data || !map_data->null_mapped))
 125                 return -EINVAL;
 126
 127         while (bytes_read != len) {
 128                 unsigned long map_len, end, start;
 129
 130                 map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 131                 end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 132                                                                 >> PAGE_SHIFT;
 133                 start = (unsigned long)ubuf >> PAGE_SHIFT;
 134
 135                 /*
 136                  * A bad offset could cause us to require BIO_MAX_PAGES + 1
 137                  * pages. If this happens we just lower the requested
 138                  * mapping len by a page so that we can fit
 139                  */
 140                 if (end - start > BIO_MAX_PAGES)
 141                         map_len -= PAGE_SIZE;
 142
 143                 ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
 144                                         gfp_mask);
 145                 if (ret < 0)
 146                         goto unmap_rq;
 147                 if (!bio)
 148                         bio = rq->bio;
 149                 bytes_read += ret;
 150                 ubuf += ret;
 151
 152                 if (map_data)
 153                         map_data->offset += ret;
 154         }
 155
 156         if (!bio_flagged(bio, BIO_USER_MAPPED))
 157                 rq->cmd_flags |= REQ_COPY_USER;
 158
 159         rq->buffer = rq->data = NULL;
 160         return 0;
 161 unmap_rq:
 162         blk_rq_unmap_user(bio);
 163         rq->bio = NULL;
 164         return ret;
 165 }
 166 EXPORT_SYMBOL(blk_rq_map_user);
 167
 168 /**
 169  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
 170  * @q:          request queue where request should be inserted
 171  * @rq:         request to map data to
 172  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
 173  * @iov:        pointer to the iovec
 174  * @iov_count:  number of elements in the iovec
 175  * @len:        I/O byte count
 176  * @gfp_mask:   memory allocation flags
 177  *
 178  * Description:
 179  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 180  *    a kernel bounce buffer is used.
 181  *
 182  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 183  *    still in process context.
 184  *
 185  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 186  *    before being submitted to the device, as pages mapped may be out of
 187  *    reach. It's the callers responsibility to make sure this happens. The
 188  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 189  *    unmapping.
 190  */
 191 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 192                         struct rq_map_data *map_data, struct sg_iovec *iov,
 193                         int iov_count, unsigned int len, gfp_t gfp_mask)
 194 {
 195         struct bio *bio;
 196         int i, read = rq_data_dir(rq) == READ;
 197         int unaligned = 0;
 198
 199         if (!iov || iov_count <= 0)
 200                 return -EINVAL;
 201
 202         for (i = 0; i < iov_count; i++) {
 203                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
 204
 205                 if (uaddr & queue_dma_alignment(q)) {
 206                         unaligned = 1;
 207                         break;
 208                 }
 209         }
 210
 211         if (unaligned || (q->dma_pad_mask & len) || map_data)
 212                 bio = bio_copy_user_iov(q, map_data, iov, iov_count, read,
 213                                         gfp_mask);
 214         else
 215                 bio = bio_map_user_iov(q, NULL, iov, iov_count, read, gfp_mask);
 216
 217         if (IS_ERR(bio))
 218                 return PTR_ERR(bio);
 219
 220         if (bio->bi_size != len) {
 221                 /*
 222                  * Grab an extra reference to this bio, as bio_unmap_user()
 223                  * expects to be able to drop it twice as it happens on the
 224                  * normal IO completion path
 225                  */
 226                 bio_get(bio);
 227                 bio_endio(bio, 0);
 228                 __blk_rq_unmap_user(bio);
 229                 return -EINVAL;
 230         }
 231
 232         if (!bio_flagged(bio, BIO_USER_MAPPED))
 233                 rq->cmd_flags |= REQ_COPY_USER;
 234
 235         blk_queue_bounce(q, &bio);
 236         bio_get(bio);
 237         blk_rq_bio_prep(q, rq, bio);
 238         rq->buffer = rq->data = NULL;
 239         return 0;
 240 }
 241 EXPORT_SYMBOL(blk_rq_map_user_iov);
 242
 243 /**
 244  * blk_rq_unmap_user - unmap a request with user data
 245  * @bio:               start of bio list
 246  *
 247  * Description:
 248  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 249  *    supply the original rq->bio from the blk_rq_map_user() return, since
 250  *    the I/O completion may have changed rq->bio.
 251  */
 252 int blk_rq_unmap_user(struct bio *bio)
 253 {
 254         struct bio *mapped_bio;
 255         int ret = 0, ret2;
 256
 257         while (bio) {
 258                 mapped_bio = bio;
 259                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 260                         mapped_bio = bio->bi_private;
 261
 262                 ret2 = __blk_rq_unmap_user(mapped_bio);
 263                 if (ret2 && !ret)
 264                         ret = ret2;
 265
 266                 mapped_bio = bio;
 267                 bio = bio->bi_next;
 268                 bio_put(mapped_bio);
 269         }
 270
 271         return ret;
 272 }
 273 EXPORT_SYMBOL(blk_rq_unmap_user);
 274
 275 /**
 276  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 277  * @q:          request queue where request should be inserted
 278  * @rq:         request to fill
 279  * @kbuf:       the kernel buffer
 280  * @len:        length of user data
 281  * @gfp_mask:   memory allocation flags
 282  *
 283  * Description:
 284  *    Data will be mapped directly if possible. Otherwise a bounce
 285  *    buffer is used.
 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
 294         if (len > (q->max_hw_sectors << 9))
 295                 return -EINVAL;
 296         if (!len || !kbuf)
 297                 return -EINVAL;
 298
 299         do_copy = !blk_rq_aligned(q, kbuf, len) || object_is_on_stack(kbuf);
 300         if (do_copy)
 301                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 302         else
 303                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 304
 305         if (IS_ERR(bio))
 306                 return PTR_ERR(bio);
 307
 308         if (rq_data_dir(rq) == WRITE)
 309                 bio->bi_rw |= (1 << BIO_RW);
 310
 311         if (do_copy)
 312                 rq->cmd_flags |= REQ_COPY_USER;
 313
 314         blk_rq_bio_prep(q, rq, bio);
 315         blk_queue_bounce(q, &rq->bio);
 316         rq->buffer = rq->data = NULL;
 317         return 0;
 318 }
 319 EXPORT_SYMBOL(blk_rq_map_kern);