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         unsigned int alignment;
  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         alignment = queue_dma_alignment(q) | q->dma_pad_mask;
  58         if (!(uaddr & alignment) && !(len & alignment))
  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 to dma_pad_mask.  As the copied
 146          * buffer is always page aligned, we know that there's enough
 147          * room for padding.  Extend the last bio and update
 148          * rq->data_len accordingly.
 149          *
 150          * On unmap, bio_uncopy_user() will use unmodified
 151          * bio_map_data pointed to by bio->bi_private.
 152          */
 153         if (len & q->dma_pad_mask) {
 154                 unsigned int pad_len = (q->dma_pad_mask & ~len) + 1;
 155                 struct bio *tail = rq->biotail;
 156
 157                 tail->bi_io_vec[tail->bi_vcnt - 1].bv_len += pad_len;
 158                 tail->bi_size += pad_len;
 159
 160                 rq->extra_len += pad_len;
 161         }
 162
 163         rq->buffer = rq->data = NULL;
 164         return 0;
 165 unmap_rq:
 166         blk_rq_unmap_user(bio);
 167         rq->bio = NULL;
 168         return ret;
 169 }
 170 EXPORT_SYMBOL(blk_rq_map_user);
 171
 172 /**
 173  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
 174  * @q:          request queue where request should be inserted
 175  * @rq:         request to map data to
 176  * @iov:        pointer to the iovec
 177  * @iov_count:  number of elements in the iovec
 178  * @len:        I/O byte count
 179  *
 180  * Description:
 181  *    Data will be mapped directly for zero copy io, if possible. Otherwise
 182  *    a kernel bounce buffer is used.
 183  *
 184  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
 185  *    still in process context.
 186  *
 187  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 188  *    before being submitted to the device, as pages mapped may be out of
 189  *    reach. It's the callers responsibility to make sure this happens. The
 190  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 191  *    unmapping.
 192  */
 193 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 194                         struct sg_iovec *iov, int iov_count, unsigned int len)
 195 {
 196         struct bio *bio;
 197
 198         if (!iov || iov_count <= 0)
 199                 return -EINVAL;
 200
 201         /* we don't allow misaligned data like bio_map_user() does.  If the
 202          * user is using sg, they're expected to know the alignment constraints
 203          * and respect them accordingly */
 204         bio = bio_map_user_iov(q, NULL, iov, iov_count,
 205                                 rq_data_dir(rq) == READ);
 206         if (IS_ERR(bio))
 207                 return PTR_ERR(bio);
 208
 209         if (bio->bi_size != len) {
 210                 bio_endio(bio, 0);
 211                 bio_unmap_user(bio);
 212                 return -EINVAL;
 213         }
 214
 215         bio_get(bio);
 216         blk_rq_bio_prep(q, rq, bio);
 217         rq->buffer = rq->data = NULL;
 218         return 0;
 219 }
 220
 221 /**
 222  * blk_rq_unmap_user - unmap a request with user data
 223  * @bio:               start of bio list
 224  *
 225  * Description:
 226  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 227  *    supply the original rq->bio from the blk_rq_map_user() return, since
 228  *    the io completion may have changed rq->bio.
 229  */
 230 int blk_rq_unmap_user(struct bio *bio)
 231 {
 232         struct bio *mapped_bio;
 233         int ret = 0, ret2;
 234
 235         while (bio) {
 236                 mapped_bio = bio;
 237                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 238                         mapped_bio = bio->bi_private;
 239
 240                 ret2 = __blk_rq_unmap_user(mapped_bio);
 241                 if (ret2 && !ret)
 242                         ret = ret2;
 243
 244                 mapped_bio = bio;
 245                 bio = bio->bi_next;
 246                 bio_put(mapped_bio);
 247         }
 248
 249         return ret;
 250 }
 251 EXPORT_SYMBOL(blk_rq_unmap_user);
 252
 253 /**
 254  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
 255  * @q:          request queue where request should be inserted
 256  * @rq:         request to fill
 257  * @kbuf:       the kernel buffer
 258  * @len:        length of user data
 259  * @gfp_mask:   memory allocation flags
 260  */
 261 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 262                     unsigned int len, gfp_t gfp_mask)
 263 {
 264         struct bio *bio;
 265
 266         if (len > (q->max_hw_sectors << 9))
 267                 return -EINVAL;
 268         if (!len || !kbuf)
 269                 return -EINVAL;
 270
 271         bio = bio_map_kern(q, kbuf, len, gfp_mask);
 272         if (IS_ERR(bio))
 273                 return PTR_ERR(bio);
 274
 275         if (rq_data_dir(rq) == WRITE)
 276                 bio->bi_rw |= (1 << BIO_RW);
 277
 278         blk_rq_bio_prep(q, rq, bio);
 279         blk_queue_bounce(q, &rq->bio);
 280         rq->buffer = rq->data = NULL;
 281         return 0;
 282 }
 283 EXPORT_SYMBOL(blk_rq_map_kern);