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 <linux/uio.h>
   9
  10 #include "blk.h"
  11
  12 static bool iovec_gap_to_prv(struct request_queue *q,
  13                              struct iovec *prv, struct iovec *cur)
  14 {
  15         unsigned long prev_end;
  16
  17         if (!queue_virt_boundary(q))
  18                 return false;
  19
  20         if (prv->iov_base == NULL && prv->iov_len == 0)
  21                 /* prv is not set - don't check */
  22                 return false;
  23
  24         prev_end = (unsigned long)(prv->iov_base + prv->iov_len);
  25
  26         return (((unsigned long)cur->iov_base & queue_virt_boundary(q)) ||
  27                 prev_end & queue_virt_boundary(q));
  28 }
  29
  30 int blk_rq_append_bio(struct request_queue *q, struct request *rq,
  31                       struct bio *bio)
  32 {
  33         if (!rq->bio)
  34                 blk_rq_bio_prep(q, rq, bio);
  35         else if (!ll_back_merge_fn(q, rq, bio))
  36                 return -EINVAL;
  37         else {
  38                 rq->biotail->bi_next = bio;
  39                 rq->biotail = bio;
  40
  41                 rq->__data_len += bio->bi_iter.bi_size;
  42         }
  43         return 0;
  44 }
  45
  46 static int __blk_rq_unmap_user(struct bio *bio)
  47 {
  48         int ret = 0;
  49
  50         if (bio) {
  51                 if (bio_flagged(bio, BIO_USER_MAPPED))
  52                         bio_unmap_user(bio);
  53                 else
  54                         ret = bio_uncopy_user(bio);
  55         }
  56
  57         return ret;
  58 }
  59
  60 static int __blk_rq_map_user_iov(struct request *rq,
  61                 struct rq_map_data *map_data, struct iov_iter *iter,
  62                 gfp_t gfp_mask, bool copy)
  63 {
  64         struct request_queue *q = rq->q;
  65         struct bio *bio, *orig_bio;
  66         int ret;
  67
  68         if (copy)
  69                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  70         else
  71                 bio = bio_map_user_iov(q, iter, gfp_mask);
  72
  73         if (IS_ERR(bio))
  74                 return PTR_ERR(bio);
  75
  76         if (map_data && map_data->null_mapped)
  77                 bio_set_flag(bio, BIO_NULL_MAPPED);
  78
  79         iov_iter_advance(iter, bio->bi_iter.bi_size);
  80         if (map_data)
  81                 map_data->offset += bio->bi_iter.bi_size;
  82
  83         orig_bio = bio;
  84         blk_queue_bounce(q, &bio);
  85
  86         /*
  87          * We link the bounce buffer in and could have to traverse it
  88          * later so we have to get a ref to prevent it from being freed
  89          */
  90         bio_get(bio);
  91
  92         ret = blk_rq_append_bio(q, rq, bio);
  93         if (ret) {
  94                 bio_endio(bio);
  95                 __blk_rq_unmap_user(orig_bio);
  96                 bio_put(bio);
  97                 return ret;
  98         }
  99
 100         return 0;
 101 }
 102
 103 /**
 104  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
 105  * @q:          request queue where request should be inserted
 106  * @rq:         request to map data to
 107  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
 108  * @iter:       iovec iterator
 109  * @gfp_mask:   memory allocation flags
 110  *
 111  * Description:
 112  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 113  *    a kernel bounce buffer is used.
 114  *
 115  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 116  *    still in process context.
 117  *
 118  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 119  *    before being submitted to the device, as pages mapped may be out of
 120  *    reach. It's the callers responsibility to make sure this happens. The
 121  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 122  *    unmapping.
 123  */
 124 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 125                         struct rq_map_data *map_data,
 126                         const struct iov_iter *iter, gfp_t gfp_mask)
 127 {
 128         struct iovec iov, prv = {.iov_base = NULL, .iov_len = 0};
 129         bool copy = (q->dma_pad_mask & iter->count) || map_data;
 130         struct bio *bio = NULL;
 131         struct iov_iter i;
 132         int ret;
 133
 134         if (!iter || !iter->count)
 135                 return -EINVAL;
 136
 137         iov_for_each(iov, i, *iter) {
 138                 unsigned long uaddr = (unsigned long) iov.iov_base;
 139
 140                 if (!iov.iov_len)
 141                         return -EINVAL;
 142
 143                 /*
 144                  * Keep going so we check length of all segments
 145                  */
 146                 if ((uaddr & queue_dma_alignment(q)) ||
 147                     iovec_gap_to_prv(q, &prv, &iov))
 148                         copy = true;
 149
 150                 prv.iov_base = iov.iov_base;
 151                 prv.iov_len = iov.iov_len;
 152         }
 153
 154         i = *iter;
 155         do {
 156                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 157                 if (ret)
 158                         goto unmap_rq;
 159                 if (!bio)
 160                         bio = rq->bio;
 161         } while (iov_iter_count(&i));
 162
 163         if (!bio_flagged(bio, BIO_USER_MAPPED))
 164                 rq->cmd_flags |= REQ_COPY_USER;
 165         return 0;
 166
 167 unmap_rq:
 168         __blk_rq_unmap_user(bio);
 169         rq->bio = NULL;
 170         return -EINVAL;
 171 }
 172 EXPORT_SYMBOL(blk_rq_map_user_iov);
 173
 174 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 175                     struct rq_map_data *map_data, void __user *ubuf,
 176                     unsigned long len, gfp_t gfp_mask)
 177 {
 178         struct iovec iov;
 179         struct iov_iter i;
 180         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 181
 182         if (unlikely(ret < 0))
 183                 return ret;
 184
 185         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 186 }
 187 EXPORT_SYMBOL(blk_rq_map_user);
 188
 189 /**
 190  * blk_rq_unmap_user - unmap a request with user data
 191  * @bio:               start of bio list
 192  *
 193  * Description:
 194  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 195  *    supply the original rq->bio from the blk_rq_map_user() return, since
 196  *    the I/O completion may have changed rq->bio.
 197  */
 198 int blk_rq_unmap_user(struct bio *bio)
 199 {
 200         struct bio *mapped_bio;
 201         int ret = 0, ret2;
 202
 203         while (bio) {
 204                 mapped_bio = bio;
 205                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 206                         mapped_bio = bio->bi_private;
 207
 208                 ret2 = __blk_rq_unmap_user(mapped_bio);
 209                 if (ret2 && !ret)
 210                         ret = ret2;
 211
 212                 mapped_bio = bio;
 213                 bio = bio->bi_next;
 214                 bio_put(mapped_bio);
 215         }
 216
 217         return ret;
 218 }
 219 EXPORT_SYMBOL(blk_rq_unmap_user);
 220
 221 /**
 222  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 223  * @q:          request queue where request should be inserted
 224  * @rq:         request to fill
 225  * @kbuf:       the kernel buffer
 226  * @len:        length of user data
 227  * @gfp_mask:   memory allocation flags
 228  *
 229  * Description:
 230  *    Data will be mapped directly if possible. Otherwise a bounce
 231  *    buffer is used. Can be called multiple times to append multiple
 232  *    buffers.
 233  */
 234 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 235                     unsigned int len, gfp_t gfp_mask)
 236 {
 237         int reading = rq_data_dir(rq) == READ;
 238         unsigned long addr = (unsigned long) kbuf;
 239         int do_copy = 0;
 240         struct bio *bio;
 241         int ret;
 242
 243         if (len > (queue_max_hw_sectors(q) << 9))
 244                 return -EINVAL;
 245         if (!len || !kbuf)
 246                 return -EINVAL;
 247
 248         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 249         if (do_copy)
 250                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 251         else
 252                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 253
 254         if (IS_ERR(bio))
 255                 return PTR_ERR(bio);
 256
 257         if (!reading)
 258                 bio->bi_rw |= REQ_WRITE;
 259
 260         if (do_copy)
 261                 rq->cmd_flags |= REQ_COPY_USER;
 262
 263         ret = blk_rq_append_bio(q, rq, bio);
 264         if (unlikely(ret)) {
 265                 /* request is too big */
 266                 bio_put(bio);
 267                 return ret;
 268         }
 269
 270         blk_queue_bounce(q, &rq->bio);
 271         return 0;
 272 }
 273 EXPORT_SYMBOL(blk_rq_map_kern);