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 /**
  61  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  62  * @q:          request queue where request should be inserted
  63  * @rq:         request to map data to
  64  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  65  * @iter:       iovec iterator
  66  * @gfp_mask:   memory allocation flags
  67  *
  68  * Description:
  69  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
  70  *    a kernel bounce buffer is used.
  71  *
  72  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
  73  *    still in process context.
  74  *
  75  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
  76  *    before being submitted to the device, as pages mapped may be out of
  77  *    reach. It's the callers responsibility to make sure this happens. The
  78  *    original bio must be passed back in to blk_rq_unmap_user() for proper
  79  *    unmapping.
  80  */
  81 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
  82                         struct rq_map_data *map_data,
  83                         const struct iov_iter *iter, gfp_t gfp_mask)
  84 {
  85         struct bio *bio;
  86         int unaligned = 0;
  87         struct iov_iter i;
  88         struct iovec iov, prv = {.iov_base = NULL, .iov_len = 0};
  89
  90         if (!iter || !iter->count)
  91                 return -EINVAL;
  92
  93         if (!iter_is_iovec(iter))
  94                 return -EINVAL;
  95
  96         iov_for_each(iov, i, *iter) {
  97                 unsigned long uaddr = (unsigned long) iov.iov_base;
  98
  99                 if (!iov.iov_len)
 100                         return -EINVAL;
 101
 102                 /*
 103                  * Keep going so we check length of all segments
 104                  */
 105                 if ((uaddr & queue_dma_alignment(q)) ||
 106                     iovec_gap_to_prv(q, &prv, &iov))
 107                         unaligned = 1;
 108
 109                 prv.iov_base = iov.iov_base;
 110                 prv.iov_len = iov.iov_len;
 111         }
 112
 113         if (unaligned || (q->dma_pad_mask & iter->count) || map_data)
 114                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
 115         else
 116                 bio = bio_map_user_iov(q, iter, gfp_mask);
 117
 118         if (IS_ERR(bio))
 119                 return PTR_ERR(bio);
 120
 121         if (map_data && map_data->null_mapped)
 122                 bio_set_flag(bio, BIO_NULL_MAPPED);
 123
 124         if (bio->bi_iter.bi_size != iter->count) {
 125                 /*
 126                  * Grab an extra reference to this bio, as bio_unmap_user()
 127                  * expects to be able to drop it twice as it happens on the
 128                  * normal IO completion path
 129                  */
 130                 bio_get(bio);
 131                 bio_endio(bio);
 132                 __blk_rq_unmap_user(bio);
 133                 return -EINVAL;
 134         }
 135
 136         if (!bio_flagged(bio, BIO_USER_MAPPED))
 137                 rq->cmd_flags |= REQ_COPY_USER;
 138
 139         blk_queue_bounce(q, &bio);
 140         bio_get(bio);
 141         blk_rq_bio_prep(q, rq, bio);
 142         return 0;
 143 }
 144 EXPORT_SYMBOL(blk_rq_map_user_iov);
 145
 146 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 147                     struct rq_map_data *map_data, void __user *ubuf,
 148                     unsigned long len, gfp_t gfp_mask)
 149 {
 150         struct iovec iov;
 151         struct iov_iter i;
 152         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 153
 154         if (unlikely(ret < 0))
 155                 return ret;
 156
 157         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 158 }
 159 EXPORT_SYMBOL(blk_rq_map_user);
 160
 161 /**
 162  * blk_rq_unmap_user - unmap a request with user data
 163  * @bio:               start of bio list
 164  *
 165  * Description:
 166  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 167  *    supply the original rq->bio from the blk_rq_map_user() return, since
 168  *    the I/O completion may have changed rq->bio.
 169  */
 170 int blk_rq_unmap_user(struct bio *bio)
 171 {
 172         struct bio *mapped_bio;
 173         int ret = 0, ret2;
 174
 175         while (bio) {
 176                 mapped_bio = bio;
 177                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 178                         mapped_bio = bio->bi_private;
 179
 180                 ret2 = __blk_rq_unmap_user(mapped_bio);
 181                 if (ret2 && !ret)
 182                         ret = ret2;
 183
 184                 mapped_bio = bio;
 185                 bio = bio->bi_next;
 186                 bio_put(mapped_bio);
 187         }
 188
 189         return ret;
 190 }
 191 EXPORT_SYMBOL(blk_rq_unmap_user);
 192
 193 /**
 194  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 195  * @q:          request queue where request should be inserted
 196  * @rq:         request to fill
 197  * @kbuf:       the kernel buffer
 198  * @len:        length of user data
 199  * @gfp_mask:   memory allocation flags
 200  *
 201  * Description:
 202  *    Data will be mapped directly if possible. Otherwise a bounce
 203  *    buffer is used. Can be called multiple times to append multiple
 204  *    buffers.
 205  */
 206 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 207                     unsigned int len, gfp_t gfp_mask)
 208 {
 209         int reading = rq_data_dir(rq) == READ;
 210         unsigned long addr = (unsigned long) kbuf;
 211         int do_copy = 0;
 212         struct bio *bio;
 213         int ret;
 214
 215         if (len > (queue_max_hw_sectors(q) << 9))
 216                 return -EINVAL;
 217         if (!len || !kbuf)
 218                 return -EINVAL;
 219
 220         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 221         if (do_copy)
 222                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 223         else
 224                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 225
 226         if (IS_ERR(bio))
 227                 return PTR_ERR(bio);
 228
 229         if (!reading)
 230                 bio->bi_rw |= REQ_WRITE;
 231
 232         if (do_copy)
 233                 rq->cmd_flags |= REQ_COPY_USER;
 234
 235         ret = blk_rq_append_bio(q, rq, bio);
 236         if (unlikely(ret)) {
 237                 /* request is too big */
 238                 bio_put(bio);
 239                 return ret;
 240         }
 241
 242         blk_queue_bounce(q, &rq->bio);
 243         return 0;
 244 }
 245 EXPORT_SYMBOL(blk_rq_map_kern);