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