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 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_iter.bi_size;
  24         }
  25         return 0;
  26 }
  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 /**
  43  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  44  * @q:          request queue where request should be inserted
  45  * @rq:         request to map data to
  46  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  47  * @iter:       iovec iterator
  48  * @gfp_mask:   memory allocation flags
  49  *
  50  * Description:
  51  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
  52  *    a kernel bounce buffer is used.
  53  *
  54  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
  55  *    still in process context.
  56  *
  57  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
  58  *    before being submitted to the device, as pages mapped may be out of
  59  *    reach. It's the callers responsibility to make sure this happens. The
  60  *    original bio must be passed back in to blk_rq_unmap_user() for proper
  61  *    unmapping.
  62  */
  63 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
  64                         struct rq_map_data *map_data,
  65                         const struct iov_iter *iter, gfp_t gfp_mask)
  66 {
  67         struct bio *bio;
  68         int unaligned = 0;
  69         struct iov_iter i;
  70         struct iovec iov;
  71
  72         if (!iter || !iter->count)
  73                 return -EINVAL;
  74
  75         iov_for_each(iov, i, *iter) {
  76                 unsigned long uaddr = (unsigned long) iov.iov_base;
  77
  78                 if (!iov.iov_len)
  79                         return -EINVAL;
  80
  81                 /*
  82                  * Keep going so we check length of all segments
  83                  */
  84                 if (uaddr & queue_dma_alignment(q))
  85                         unaligned = 1;
  86         }
  87
  88         if (unaligned || (q->dma_pad_mask & iter->count) || map_data)
  89                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  90         else
  91                 bio = bio_map_user_iov(q, iter, gfp_mask);
  92
  93         if (IS_ERR(bio))
  94                 return PTR_ERR(bio);
  95
  96         if (map_data && map_data->null_mapped)
  97                 bio->bi_flags |= (1 << BIO_NULL_MAPPED);
  98
  99         if (bio->bi_iter.bi_size != iter->count) {
 100                 /*
 101                  * Grab an extra reference to this bio, as bio_unmap_user()
 102                  * expects to be able to drop it twice as it happens on the
 103                  * normal IO completion path
 104                  */
 105                 bio_get(bio);
 106                 bio_endio(bio, 0);
 107                 __blk_rq_unmap_user(bio);
 108                 return -EINVAL;
 109         }
 110
 111         if (!bio_flagged(bio, BIO_USER_MAPPED))
 112                 rq->cmd_flags |= REQ_COPY_USER;
 113
 114         blk_queue_bounce(q, &bio);
 115         bio_get(bio);
 116         blk_rq_bio_prep(q, rq, bio);
 117         return 0;
 118 }
 119 EXPORT_SYMBOL(blk_rq_map_user_iov);
 120
 121 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 122                     struct rq_map_data *map_data, void __user *ubuf,
 123                     unsigned long len, gfp_t gfp_mask)
 124 {
 125         struct iovec iov;
 126         struct iov_iter i;
 127
 128         iov.iov_base = ubuf;
 129         iov.iov_len = len;
 130         iov_iter_init(&i, rq_data_dir(rq), &iov, 1, len);
 131
 132         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 133 }
 134 EXPORT_SYMBOL(blk_rq_map_user);
 135
 136 /**
 137  * blk_rq_unmap_user - unmap a request with user data
 138  * @bio:               start of bio list
 139  *
 140  * Description:
 141  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 142  *    supply the original rq->bio from the blk_rq_map_user() return, since
 143  *    the I/O completion may have changed rq->bio.
 144  */
 145 int blk_rq_unmap_user(struct bio *bio)
 146 {
 147         struct bio *mapped_bio;
 148         int ret = 0, ret2;
 149
 150         while (bio) {
 151                 mapped_bio = bio;
 152                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 153                         mapped_bio = bio->bi_private;
 154
 155                 ret2 = __blk_rq_unmap_user(mapped_bio);
 156                 if (ret2 && !ret)
 157                         ret = ret2;
 158
 159                 mapped_bio = bio;
 160                 bio = bio->bi_next;
 161                 bio_put(mapped_bio);
 162         }
 163
 164         return ret;
 165 }
 166 EXPORT_SYMBOL(blk_rq_unmap_user);
 167
 168 /**
 169  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 170  * @q:          request queue where request should be inserted
 171  * @rq:         request to fill
 172  * @kbuf:       the kernel buffer
 173  * @len:        length of user data
 174  * @gfp_mask:   memory allocation flags
 175  *
 176  * Description:
 177  *    Data will be mapped directly if possible. Otherwise a bounce
 178  *    buffer is used. Can be called multiple times to append multiple
 179  *    buffers.
 180  */
 181 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 182                     unsigned int len, gfp_t gfp_mask)
 183 {
 184         int reading = rq_data_dir(rq) == READ;
 185         unsigned long addr = (unsigned long) kbuf;
 186         int do_copy = 0;
 187         struct bio *bio;
 188         int ret;
 189
 190         if (len > (queue_max_hw_sectors(q) << 9))
 191                 return -EINVAL;
 192         if (!len || !kbuf)
 193                 return -EINVAL;
 194
 195         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 196         if (do_copy)
 197                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 198         else
 199                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 200
 201         if (IS_ERR(bio))
 202                 return PTR_ERR(bio);
 203
 204         if (!reading)
 205                 bio->bi_rw |= REQ_WRITE;
 206
 207         if (do_copy)
 208                 rq->cmd_flags |= REQ_COPY_USER;
 209
 210         ret = blk_rq_append_bio(q, rq, bio);
 211         if (unlikely(ret)) {
 212                 /* request is too big */
 213                 bio_put(bio);
 214                 return ret;
 215         }
 216
 217         blk_queue_bounce(q, &rq->bio);
 218         return 0;
 219 }
 220 EXPORT_SYMBOL(blk_rq_map_kern);