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