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->raw_data_len += bio->bi_size;
  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                              void __user *ubuf, unsigned int len)
  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 (!(uaddr & queue_dma_alignment(q)) &&
  58             !(len & queue_dma_alignment(q)))
  59                 bio = bio_map_user(q, NULL, uaddr, len, reading);
  60         else
  61                 bio = bio_copy_user(q, uaddr, len, reading);
  62
  63         if (IS_ERR(bio))
  64                 return PTR_ERR(bio);
  65
  66         orig_bio = bio;
  67         blk_queue_bounce(q, &bio);
  68
  69         /*
  70          * We link the bounce buffer in and could have to traverse it
  71          * later so we have to get a ref to prevent it from being freed
  72          */
  73         bio_get(bio);
  74
  75         ret = blk_rq_append_bio(q, rq, bio);
  76         if (!ret)
  77                 return bio->bi_size;
  78
  79         /* if it was boucned we must call the end io function */
  80         bio_endio(bio, 0);
  81         __blk_rq_unmap_user(orig_bio);
  82         bio_put(bio);
  83         return ret;
  84 }
  85
  86 /**
  87  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
  88  * @q:          request queue where request should be inserted
  89  * @rq:         request structure to fill
  90  * @ubuf:       the user buffer
  91  * @len:        length of user data
  92  *
  93  * Description:
  94  *    Data will be mapped directly for zero copy io, if possible. Otherwise
  95  *    a kernel bounce buffer is used.
  96  *
  97  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
  98  *    still in process context.
  99  *
 100  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 101  *    before being submitted to the device, as pages mapped may be out of
 102  *    reach. It's the callers responsibility to make sure this happens. The
 103  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 104  *    unmapping.
 105  */
 106 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 107                     void __user *ubuf, unsigned long len)
 108 {
 109         unsigned long bytes_read = 0;
 110         struct bio *bio = NULL;
 111         int ret;
 112
 113         if (len > (q->max_hw_sectors << 9))
 114                 return -EINVAL;
 115         if (!len || !ubuf)
 116                 return -EINVAL;
 117
 118         while (bytes_read != len) {
 119                 unsigned long map_len, end, start;
 120
 121                 map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 122                 end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 123                                                                 >> PAGE_SHIFT;
 124                 start = (unsigned long)ubuf >> PAGE_SHIFT;
 125
 126                 /*
 127                  * A bad offset could cause us to require BIO_MAX_PAGES + 1
 128                  * pages. If this happens we just lower the requested
 129                  * mapping len by a page so that we can fit
 130                  */
 131                 if (end - start > BIO_MAX_PAGES)
 132                         map_len -= PAGE_SIZE;
 133
 134                 ret = __blk_rq_map_user(q, rq, ubuf, map_len);
 135                 if (ret < 0)
 136                         goto unmap_rq;
 137                 if (!bio)
 138                         bio = rq->bio;
 139                 bytes_read += ret;
 140                 ubuf += ret;
 141         }
 142
 143         /*
 144          * __blk_rq_map_user() copies the buffers if starting address
 145          * or length isn't aligned.  As the copied buffer is always
 146          * page aligned, we know that there's enough room for padding.
 147          * Extend the last bio and update rq->data_len accordingly.
 148          *
 149          * On unmap, bio_uncopy_user() will use unmodified
 150          * bio_map_data pointed to by bio->bi_private.
 151          */
 152         if (len & queue_dma_alignment(q)) {
 153                 unsigned int pad_len = (queue_dma_alignment(q) & ~len) + 1;
 154                 struct bio *bio = rq->biotail;
 155
 156                 bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len;
 157                 bio->bi_size += pad_len;
 158                 rq->data_len += pad_len;
 159         }
 160
 161         rq->buffer = rq->data = NULL;
 162         return 0;
 163 unmap_rq:
 164         blk_rq_unmap_user(bio);
 165         rq->bio = NULL;
 166         return ret;
 167 }
 168 EXPORT_SYMBOL(blk_rq_map_user);
 169
 170 /**
 171  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
 172  * @q:          request queue where request should be inserted
 173  * @rq:         request to map data to
 174  * @iov:        pointer to the iovec
 175  * @iov_count:  number of elements in the iovec
 176  * @len:        I/O byte count
 177  *
 178  * Description:
 179  *    Data will be mapped directly for zero copy io, 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 io, 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 sg_iovec *iov, int iov_count, unsigned int len)
 193 {
 194         struct bio *bio;
 195
 196         if (!iov || iov_count <= 0)
 197                 return -EINVAL;
 198
 199         /* we don't allow misaligned data like bio_map_user() does.  If the
 200          * user is using sg, they're expected to know the alignment constraints
 201          * and respect them accordingly */
 202         bio = bio_map_user_iov(q, NULL, iov, iov_count,
 203                                 rq_data_dir(rq) == READ);
 204         if (IS_ERR(bio))
 205                 return PTR_ERR(bio);
 206
 207         if (bio->bi_size != len) {
 208                 bio_endio(bio, 0);
 209                 bio_unmap_user(bio);
 210                 return -EINVAL;
 211         }
 212
 213         bio_get(bio);
 214         blk_rq_bio_prep(q, rq, bio);
 215         rq->buffer = rq->data = NULL;
 216         return 0;
 217 }
 218 EXPORT_SYMBOL(blk_rq_map_user_iov);
 219
 220 /**
 221  * blk_rq_unmap_user - unmap a request with user data
 222  * @bio:               start of bio list
 223  *
 224  * Description:
 225  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 226  *    supply the original rq->bio from the blk_rq_map_user() return, since
 227  *    the io completion may have changed rq->bio.
 228  */
 229 int blk_rq_unmap_user(struct bio *bio)
 230 {
 231         struct bio *mapped_bio;
 232         int ret = 0, ret2;
 233
 234         while (bio) {
 235                 mapped_bio = bio;
 236                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 237                         mapped_bio = bio->bi_private;
 238
 239                 ret2 = __blk_rq_unmap_user(mapped_bio);
 240                 if (ret2 && !ret)
 241                         ret = ret2;
 242
 243                 mapped_bio = bio;
 244                 bio = bio->bi_next;
 245                 bio_put(mapped_bio);
 246         }
 247
 248         return ret;
 249 }
 250 EXPORT_SYMBOL(blk_rq_unmap_user);
 251
 252 /**
 253  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
 254  * @q:          request queue where request should be inserted
 255  * @rq:         request to fill
 256  * @kbuf:       the kernel buffer
 257  * @len:        length of user data
 258  * @gfp_mask:   memory allocation flags
 259  */
 260 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 261                     unsigned int len, gfp_t gfp_mask)
 262 {
 263         struct bio *bio;
 264
 265         if (len > (q->max_hw_sectors << 9))
 266                 return -EINVAL;
 267         if (!len || !kbuf)
 268                 return -EINVAL;
 269
 270         bio = bio_map_kern(q, kbuf, len, gfp_mask);
 271         if (IS_ERR(bio))
 272                 return PTR_ERR(bio);
 273
 274         if (rq_data_dir(rq) == WRITE)
 275                 bio->bi_rw |= (1 << BIO_RW);
 276
 277         blk_rq_bio_prep(q, rq, bio);
 278         blk_queue_bounce(q, &rq->bio);
 279         rq->buffer = rq->data = NULL;
 280         return 0;
 281 }
 282 EXPORT_SYMBOL(blk_rq_map_kern);