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 static int __blk_rq_map_user_iov(struct request *rq,
  43                 struct rq_map_data *map_data, struct iov_iter *iter,
  44                 gfp_t gfp_mask, bool copy)
  45 {
  46         struct request_queue *q = rq->q;
  47         struct bio *bio, *orig_bio;
  48         int ret;
  49
  50         if (copy)
  51                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  52         else
  53                 bio = bio_map_user_iov(q, iter, gfp_mask);
  54
  55         if (IS_ERR(bio))
  56                 return PTR_ERR(bio);
  57
  58         if (map_data && map_data->null_mapped)
  59                 bio_set_flag(bio, BIO_NULL_MAPPED);
  60
  61         iov_iter_advance(iter, bio->bi_iter.bi_size);
  62         if (map_data)
  63                 map_data->offset += bio->bi_iter.bi_size;
  64
  65         orig_bio = bio;
  66         blk_queue_bounce(q, &bio);
  67
  68         /*
  69          * We link the bounce buffer in and could have to traverse it
  70          * later so we have to get a ref to prevent it from being freed
  71          */
  72         bio_get(bio);
  73
  74         ret = blk_rq_append_bio(q, rq, bio);
  75         if (ret) {
  76                 bio_endio(bio);
  77                 __blk_rq_unmap_user(orig_bio);
  78                 bio_put(bio);
  79                 return ret;
  80         }
  81
  82         return 0;
  83 }
  84
  85 /**
  86  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  87  * @q:          request queue where request should be inserted
  88  * @rq:         request to map data to
  89  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  90  * @iter:       iovec iterator
  91  * @gfp_mask:   memory allocation flags
  92  *
  93  * Description:
  94  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
  95  *    a kernel bounce buffer is used.
  96  *
  97  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
  98  *    still in process context.
  99  *
 100  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 101  *    before being submitted to the device, as pages mapped may be out of
 102  *    reach. It's the callers responsibility to make sure this happens. The
 103  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 104  *    unmapping.
 105  */
 106 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 107                         struct rq_map_data *map_data,
 108                         const struct iov_iter *iter, gfp_t gfp_mask)
 109 {
 110         bool copy = false;
 111         unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 112         struct bio *bio = NULL;
 113         struct iov_iter i;
 114         int ret;
 115
 116         if (map_data)
 117                 copy = true;
 118         else if (iov_iter_alignment(iter) & align)
 119                 copy = true;
 120         else if (queue_virt_boundary(q))
 121                 copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 122
 123         i = *iter;
 124         do {
 125                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 126                 if (ret)
 127                         goto unmap_rq;
 128                 if (!bio)
 129                         bio = rq->bio;
 130         } while (iov_iter_count(&i));
 131
 132         if (!bio_flagged(bio, BIO_USER_MAPPED))
 133                 rq->cmd_flags |= REQ_COPY_USER;
 134         return 0;
 135
 136 unmap_rq:
 137         __blk_rq_unmap_user(bio);
 138         rq->bio = NULL;
 139         return -EINVAL;
 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);