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         /*
 143          * __blk_rq_map_user() copies the buffers if starting address
 144          * or length isn't aligned.  As the copied buffer is always
 145          * page aligned, we know that there's enough room for padding.
 146          * Extend the last bio and update rq->data_len accordingly.
 147          *
 148          * On unmap, bio_uncopy_user() will use unmodified
 149          * bio_map_data pointed to by bio->bi_private.
 150          */
 151         if (len & queue_dma_alignment(q)) {
 152                 unsigned int pad_len = (queue_dma_alignment(q) & ~len) + 1;
 153
 154                 rq->extra_len += pad_len;
 155         }
 156
 157         rq->buffer = rq->data = NULL;
 158         return 0;
 159 unmap_rq:
 160         blk_rq_unmap_user(bio);
 161         rq->bio = NULL;
 162         return ret;
 163 }
 164 EXPORT_SYMBOL(blk_rq_map_user);
 165
 166 /**
 167  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
 168  * @q:          request queue where request should be inserted
 169  * @rq:         request to map data to
 170  * @iov:        pointer to the iovec
 171  * @iov_count:  number of elements in the iovec
 172  * @len:        I/O byte count
 173  *
 174  * Description:
 175  *    Data will be mapped directly for zero copy io, if possible. Otherwise
 176  *    a kernel bounce buffer is used.
 177  *
 178  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
 179  *    still in process context.
 180  *
 181  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 182  *    before being submitted to the device, as pages mapped may be out of
 183  *    reach. It's the callers responsibility to make sure this happens. The
 184  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 185  *    unmapping.
 186  */
 187 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 188                         struct sg_iovec *iov, int iov_count, unsigned int len)
 189 {
 190         struct bio *bio;
 191
 192         if (!iov || iov_count <= 0)
 193                 return -EINVAL;
 194
 195         /* we don't allow misaligned data like bio_map_user() does.  If the
 196          * user is using sg, they're expected to know the alignment constraints
 197          * and respect them accordingly */
 198         bio = bio_map_user_iov(q, NULL, iov, iov_count,
 199                                 rq_data_dir(rq) == READ);
 200         if (IS_ERR(bio))
 201                 return PTR_ERR(bio);
 202
 203         if (bio->bi_size != len) {
 204                 bio_endio(bio, 0);
 205                 bio_unmap_user(bio);
 206                 return -EINVAL;
 207         }
 208
 209         bio_get(bio);
 210         blk_rq_bio_prep(q, rq, bio);
 211         rq->buffer = rq->data = NULL;
 212         return 0;
 213 }
 214 EXPORT_SYMBOL(blk_rq_map_user_iov);
 215
 216 /**
 217  * blk_rq_unmap_user - unmap a request with user data
 218  * @bio:               start of bio list
 219  *
 220  * Description:
 221  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 222  *    supply the original rq->bio from the blk_rq_map_user() return, since
 223  *    the io completion may have changed rq->bio.
 224  */
 225 int blk_rq_unmap_user(struct bio *bio)
 226 {
 227         struct bio *mapped_bio;
 228         int ret = 0, ret2;
 229
 230         while (bio) {
 231                 mapped_bio = bio;
 232                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 233                         mapped_bio = bio->bi_private;
 234
 235                 ret2 = __blk_rq_unmap_user(mapped_bio);
 236                 if (ret2 && !ret)
 237                         ret = ret2;
 238
 239                 mapped_bio = bio;
 240                 bio = bio->bi_next;
 241                 bio_put(mapped_bio);
 242         }
 243
 244         return ret;
 245 }
 246 EXPORT_SYMBOL(blk_rq_unmap_user);
 247
 248 /**
 249  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
 250  * @q:          request queue where request should be inserted
 251  * @rq:         request to fill
 252  * @kbuf:       the kernel buffer
 253  * @len:        length of user data
 254  * @gfp_mask:   memory allocation flags
 255  */
 256 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 257                     unsigned int len, gfp_t gfp_mask)
 258 {
 259         struct bio *bio;
 260
 261         if (len > (q->max_hw_sectors << 9))
 262                 return -EINVAL;
 263         if (!len || !kbuf)
 264                 return -EINVAL;
 265
 266         bio = bio_map_kern(q, kbuf, len, gfp_mask);
 267         if (IS_ERR(bio))
 268                 return PTR_ERR(bio);
 269
 270         if (rq_data_dir(rq) == WRITE)
 271                 bio->bi_rw |= (1 << BIO_RW);
 272
 273         blk_rq_bio_prep(q, rq, bio);
 274         blk_queue_bounce(q, &rq->bio);
 275         rq->buffer = rq->data = NULL;
 276         return 0;
 277 }
 278 EXPORT_SYMBOL(blk_rq_map_kern);