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                              void __user *ubuf, unsigned int len)
  45 {
  46         unsigned long uaddr;
  47         unsigned int alignment;
  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         alignment = queue_dma_alignment(q) | q->dma_pad_mask;
  59         if (!(uaddr & alignment) && !(len & alignment))
  60                 bio = bio_map_user(q, NULL, uaddr, len, reading);
  61         else
  62                 bio = bio_copy_user(q, uaddr, len, reading);
  63
  64         if (IS_ERR(bio))
  65                 return PTR_ERR(bio);
  66
  67         orig_bio = bio;
  68         blk_queue_bounce(q, &bio);
  69
  70         /*
  71          * We link the bounce buffer in and could have to traverse it
  72          * later so we have to get a ref to prevent it from being freed
  73          */
  74         bio_get(bio);
  75
  76         ret = blk_rq_append_bio(q, rq, bio);
  77         if (!ret)
  78                 return bio->bi_size;
  79
  80         /* if it was boucned we must call the end io function */
  81         bio_endio(bio, 0);
  82         __blk_rq_unmap_user(orig_bio);
  83         bio_put(bio);
  84         return ret;
  85 }
  86
  87 /**
  88  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
  89  * @q:          request queue where request should be inserted
  90  * @rq:         request structure to fill
  91  * @ubuf:       the user buffer
  92  * @len:        length of user data
  93  *
  94  * Description:
  95  *    Data will be mapped directly for zero copy io, if possible. Otherwise
  96  *    a kernel bounce buffer is used.
  97  *
  98  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
  99  *    still in process context.
 100  *
 101  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 102  *    before being submitted to the device, as pages mapped may be out of
 103  *    reach. It's the callers responsibility to make sure this happens. The
 104  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 105  *    unmapping.
 106  */
 107 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 108                     void __user *ubuf, unsigned long len)
 109 {
 110         unsigned long bytes_read = 0;
 111         struct bio *bio = NULL;
 112         int ret;
 113
 114         if (len > (q->max_hw_sectors << 9))
 115                 return -EINVAL;
 116         if (!len || !ubuf)
 117                 return -EINVAL;
 118
 119         while (bytes_read != len) {
 120                 unsigned long map_len, end, start;
 121
 122                 map_len = min_t(unsigned long, len - bytes_read, BIO_MAX_SIZE);
 123                 end = ((unsigned long)ubuf + map_len + PAGE_SIZE - 1)
 124                                                                 >> PAGE_SHIFT;
 125                 start = (unsigned long)ubuf >> PAGE_SHIFT;
 126
 127                 /*
 128                  * A bad offset could cause us to require BIO_MAX_PAGES + 1
 129                  * pages. If this happens we just lower the requested
 130                  * mapping len by a page so that we can fit
 131                  */
 132                 if (end - start > BIO_MAX_PAGES)
 133                         map_len -= PAGE_SIZE;
 134
 135                 ret = __blk_rq_map_user(q, rq, ubuf, map_len);
 136                 if (ret < 0)
 137                         goto unmap_rq;
 138                 if (!bio)
 139                         bio = rq->bio;
 140                 bytes_read += ret;
 141                 ubuf += ret;
 142         }
 143
 144         if (!bio_flagged(bio, BIO_USER_MAPPED))
 145                 rq->cmd_flags |= REQ_COPY_USER;
 146
 147         rq->buffer = rq->data = NULL;
 148         return 0;
 149 unmap_rq:
 150         blk_rq_unmap_user(bio);
 151         rq->bio = NULL;
 152         return ret;
 153 }
 154 EXPORT_SYMBOL(blk_rq_map_user);
 155
 156 /**
 157  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
 158  * @q:          request queue where request should be inserted
 159  * @rq:         request to map data to
 160  * @iov:        pointer to the iovec
 161  * @iov_count:  number of elements in the iovec
 162  * @len:        I/O byte count
 163  *
 164  * Description:
 165  *    Data will be mapped directly for zero copy io, if possible. Otherwise
 166  *    a kernel bounce buffer is used.
 167  *
 168  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
 169  *    still in process context.
 170  *
 171  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 172  *    before being submitted to the device, as pages mapped may be out of
 173  *    reach. It's the callers responsibility to make sure this happens. The
 174  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 175  *    unmapping.
 176  */
 177 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 178                         struct sg_iovec *iov, int iov_count, unsigned int len)
 179 {
 180         struct bio *bio;
 181         int i, read = rq_data_dir(rq) == READ;
 182         int unaligned = 0;
 183
 184         if (!iov || iov_count <= 0)
 185                 return -EINVAL;
 186
 187         for (i = 0; i < iov_count; i++) {
 188                 unsigned long uaddr = (unsigned long)iov[i].iov_base;
 189
 190                 if (uaddr & queue_dma_alignment(q)) {
 191                         unaligned = 1;
 192                         break;
 193                 }
 194         }
 195
 196         if (unaligned || (q->dma_pad_mask & len))
 197                 bio = bio_copy_user_iov(q, iov, iov_count, read);
 198         else
 199                 bio = bio_map_user_iov(q, NULL, iov, iov_count, read);
 200
 201         if (IS_ERR(bio))
 202                 return PTR_ERR(bio);
 203
 204         if (bio->bi_size != len) {
 205                 bio_endio(bio, 0);
 206                 bio_unmap_user(bio);
 207                 return -EINVAL;
 208         }
 209
 210         if (!bio_flagged(bio, BIO_USER_MAPPED))
 211                 rq->cmd_flags |= REQ_COPY_USER;
 212
 213         bio_get(bio);
 214         blk_rq_bio_prep(q, rq, bio);
 215         rq->buffer = rq->data = NULL;
 216         return 0;
 217 }
 218
 219 /**
 220  * blk_rq_unmap_user - unmap a request with user data
 221  * @bio:               start of bio list
 222  *
 223  * Description:
 224  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 225  *    supply the original rq->bio from the blk_rq_map_user() return, since
 226  *    the io completion may have changed rq->bio.
 227  */
 228 int blk_rq_unmap_user(struct bio *bio)
 229 {
 230         struct bio *mapped_bio;
 231         int ret = 0, ret2;
 232
 233         while (bio) {
 234                 mapped_bio = bio;
 235                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 236                         mapped_bio = bio->bi_private;
 237
 238                 ret2 = __blk_rq_unmap_user(mapped_bio);
 239                 if (ret2 && !ret)
 240                         ret = ret2;
 241
 242                 mapped_bio = bio;
 243                 bio = bio->bi_next;
 244                 bio_put(mapped_bio);
 245         }
 246
 247         return ret;
 248 }
 249 EXPORT_SYMBOL(blk_rq_unmap_user);
 250
 251 /**
 252  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
 253  * @q:          request queue where request should be inserted
 254  * @rq:         request to fill
 255  * @kbuf:       the kernel buffer
 256  * @len:        length of user data
 257  * @gfp_mask:   memory allocation flags
 258  */
 259 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 260                     unsigned int len, gfp_t gfp_mask)
 261 {
 262         struct bio *bio;
 263
 264         if (len > (q->max_hw_sectors << 9))
 265                 return -EINVAL;
 266         if (!len || !kbuf)
 267                 return -EINVAL;
 268
 269         bio = bio_map_kern(q, kbuf, len, gfp_mask);
 270         if (IS_ERR(bio))
 271                 return PTR_ERR(bio);
 272
 273         if (rq_data_dir(rq) == WRITE)
 274                 bio->bi_rw |= (1 << BIO_RW);
 275
 276         blk_rq_bio_prep(q, rq, bio);
 277         blk_queue_bounce(q, &rq->bio);
 278         rq->buffer = rq->data = NULL;
 279         return 0;
 280 }
 281 EXPORT_SYMBOL(blk_rq_map_kern);