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
   9 #include "blk.h"
  10
  11 int blk_rq_append_bio(struct request_queue *q, struct request *rq,
  12                       struct bio *bio)
  13 {
  14         if (!rq->bio)
  15                 blk_rq_bio_prep(q, rq, bio);
  16         else if (!ll_back_merge_fn(q, rq, bio))
  17                 return -EINVAL;
  18         else {
  19                 rq->biotail->bi_next = bio;
  20                 rq->biotail = bio;
  21
  22                 rq->data_len += bio->bi_size;
  23         }
  24         return 0;
  25 }
  26 EXPORT_SYMBOL(blk_rq_append_bio);
  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                              void __user *ubuf, unsigned int len)
  44 {
  45         unsigned long uaddr;
  46         struct bio *bio, *orig_bio;
  47         int reading, ret;
  48
  49         reading = rq_data_dir(rq) == READ;
  50
  51         /*
  52          * if alignment requirement is satisfied, map in user pages for
  53          * direct dma. else, set up kernel bounce buffers
  54          */
  55         uaddr = (unsigned long) ubuf;
  56         if (!(uaddr & queue_dma_alignment(q)) &&
  57             !(len & queue_dma_alignment(q)))
  58                 bio = bio_map_user(q, NULL, uaddr, len, reading);
  59         else
  60                 bio = bio_copy_user(q, uaddr, len, reading);
  61
  62         if (IS_ERR(bio))
  63                 return PTR_ERR(bio);
  64
  65         orig_bio = bio;
  66         blk_queue_bounce(q, &bio);
  67
  68         /*
  69          * We link the bounce buffer in and could have to traverse it
  70          * later so we have to get a ref to prevent it from being freed
  71          */
  72         bio_get(bio);
  73
  74         ret = blk_rq_append_bio(q, rq, bio);
  75         if (!ret)
  76                 return bio->bi_size;
  77
  78         /* if it was boucned we must call the end io function */
  79         bio_endio(bio, 0);
  80         __blk_rq_unmap_user(orig_bio);
  81         bio_put(bio);
  82         return ret;
  83 }
  84
  85 /**
  86  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
  87  * @q:          request queue where request should be inserted
  88  * @rq:         request structure to fill
  89  * @ubuf:       the user buffer
  90  * @len:        length of user data
  91  *
  92  * Description:
  93  *    Data will be mapped directly for zero copy io, if possible. Otherwise
  94  *    a kernel bounce buffer is used.
  95  *
  96  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
  97  *    still in process context.
  98  *
  99  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 100  *    before being submitted to the device, as pages mapped may be out of
 101  *    reach. It's the callers responsibility to make sure this happens. The
 102  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 103  *    unmapping.
 104  */
 105 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 106                     void __user *ubuf, unsigned long len)
 107 {
 108         unsigned long bytes_read = 0;
 109         struct bio *bio = NULL;
 110         int ret;
 111
 112         if (len > (q->max_hw_sectors << 9))
 113                 return -EINVAL;
 114         if (!len || !ubuf)
 115                 return -EINVAL;
 116
 117         while (bytes_read != len) {
 118                 unsigned long map_len, end, start;
 119
 120                 map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 121                 end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 122                                                                 >> PAGE_SHIFT;
 123                 start = (unsigned long)ubuf >> PAGE_SHIFT;
 124
 125                 /*
 126                  * A bad offset could cause us to require BIO_MAX_PAGES + 1
 127                  * pages. If this happens we just lower the requested
 128                  * mapping len by a page so that we can fit
 129                  */
 130                 if (end - start > BIO_MAX_PAGES)
 131                         map_len -= PAGE_SIZE;
 132
 133                 ret = __blk_rq_map_user(q, rq, ubuf, map_len);
 134                 if (ret < 0)
 135                         goto unmap_rq;
 136                 if (!bio)
 137                         bio = rq->bio;
 138                 bytes_read += ret;
 139                 ubuf += ret;
 140         }
 141
 142         rq->buffer = rq->data = NULL;
 143         return 0;
 144 unmap_rq:
 145         blk_rq_unmap_user(bio);
 146         return ret;
 147 }
 148 EXPORT_SYMBOL(blk_rq_map_user);
 149
 150 /**
 151  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
 152  * @q:          request queue where request should be inserted
 153  * @rq:         request to map data to
 154  * @iov:        pointer to the iovec
 155  * @iov_count:  number of elements in the iovec
 156  * @len:        I/O byte count
 157  *
 158  * Description:
 159  *    Data will be mapped directly for zero copy io, if possible. Otherwise
 160  *    a kernel bounce buffer is used.
 161  *
 162  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
 163  *    still in process context.
 164  *
 165  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 166  *    before being submitted to the device, as pages mapped may be out of
 167  *    reach. It's the callers responsibility to make sure this happens. The
 168  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 169  *    unmapping.
 170  */
 171 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 172                         struct sg_iovec *iov, int iov_count, unsigned int len)
 173 {
 174         struct bio *bio;
 175
 176         if (!iov || iov_count <= 0)
 177                 return -EINVAL;
 178
 179         /* we don't allow misaligned data like bio_map_user() does.  If the
 180          * user is using sg, they're expected to know the alignment constraints
 181          * and respect them accordingly */
 182         bio = bio_map_user_iov(q, NULL, iov, iov_count,
 183                                 rq_data_dir(rq) == READ);
 184         if (IS_ERR(bio))
 185                 return PTR_ERR(bio);
 186
 187         if (bio->bi_size != len) {
 188                 bio_endio(bio, 0);
 189                 bio_unmap_user(bio);
 190                 return -EINVAL;
 191         }
 192
 193         bio_get(bio);
 194         blk_rq_bio_prep(q, rq, bio);
 195         rq->buffer = rq->data = NULL;
 196         return 0;
 197 }
 198 EXPORT_SYMBOL(blk_rq_map_user_iov);
 199
 200 /**
 201  * blk_rq_unmap_user - unmap a request with user data
 202  * @bio:               start of bio list
 203  *
 204  * Description:
 205  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 206  *    supply the original rq->bio from the blk_rq_map_user() return, since
 207  *    the io completion may have changed rq->bio.
 208  */
 209 int blk_rq_unmap_user(struct bio *bio)
 210 {
 211         struct bio *mapped_bio;
 212         int ret = 0, ret2;
 213
 214         while (bio) {
 215                 mapped_bio = bio;
 216                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 217                         mapped_bio = bio->bi_private;
 218
 219                 ret2 = __blk_rq_unmap_user(mapped_bio);
 220                 if (ret2 && !ret)
 221                         ret = ret2;
 222
 223                 mapped_bio = bio;
 224                 bio = bio->bi_next;
 225                 bio_put(mapped_bio);
 226         }
 227
 228         return ret;
 229 }
 230 EXPORT_SYMBOL(blk_rq_unmap_user);
 231
 232 /**
 233  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
 234  * @q:          request queue where request should be inserted
 235  * @rq:         request to fill
 236  * @kbuf:       the kernel buffer
 237  * @len:        length of user data
 238  * @gfp_mask:   memory allocation flags
 239  */
 240 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 241                     unsigned int len, gfp_t gfp_mask)
 242 {
 243         struct bio *bio;
 244
 245         if (len > (q->max_hw_sectors << 9))
 246                 return -EINVAL;
 247         if (!len || !kbuf)
 248                 return -EINVAL;
 249
 250         bio = bio_map_kern(q, kbuf, len, gfp_mask);
 251         if (IS_ERR(bio))
 252                 return PTR_ERR(bio);
 253
 254         if (rq_data_dir(rq) == WRITE)
 255                 bio->bi_rw |= (1 << BIO_RW);
 256
 257         blk_rq_bio_prep(q, rq, bio);
 258         blk_queue_bounce(q, &rq->bio);
 259         rq->buffer = rq->data = NULL;
 260         return 0;
 261 }
 262 EXPORT_SYMBOL(blk_rq_map_kern);