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 /*
  13  * Append a bio to a passthrough request.  Only works can be merged into
  14  * the request based on the driver constraints.
  15  */
  16 int blk_rq_append_bio(struct request *rq, struct bio *bio)
  17 {
  18         if (!rq->bio) {
  19                 blk_rq_bio_prep(rq->q, rq, bio);
  20         } else {
  21                 if (!ll_back_merge_fn(rq->q, rq, bio))
  22                         return -EINVAL;
  23
  24                 rq->biotail->bi_next = bio;
  25                 rq->biotail = bio;
  26                 rq->__data_len += bio->bi_iter.bi_size;
  27         }
  28
  29         return 0;
  30 }
  31 EXPORT_SYMBOL(blk_rq_append_bio);
  32
  33 static int __blk_rq_unmap_user(struct bio *bio)
  34 {
  35         int ret = 0;
  36
  37         if (bio) {
  38                 if (bio_flagged(bio, BIO_USER_MAPPED))
  39                         bio_unmap_user(bio);
  40                 else
  41                         ret = bio_uncopy_user(bio);
  42         }
  43
  44         return ret;
  45 }
  46
  47 static int __blk_rq_map_user_iov(struct request *rq,
  48                 struct rq_map_data *map_data, struct iov_iter *iter,
  49                 gfp_t gfp_mask, bool copy)
  50 {
  51         struct request_queue *q = rq->q;
  52         struct bio *bio, *orig_bio;
  53         int ret;
  54
  55         if (copy)
  56                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  57         else
  58                 bio = bio_map_user_iov(q, iter, gfp_mask);
  59
  60         if (IS_ERR(bio))
  61                 return PTR_ERR(bio);
  62
  63         if (map_data && map_data->null_mapped)
  64                 bio_set_flag(bio, BIO_NULL_MAPPED);
  65
  66         iov_iter_advance(iter, bio->bi_iter.bi_size);
  67         if (map_data)
  68                 map_data->offset += bio->bi_iter.bi_size;
  69
  70         orig_bio = bio;
  71         blk_queue_bounce(q, &bio);
  72
  73         /*
  74          * We link the bounce buffer in and could have to traverse it
  75          * later so we have to get a ref to prevent it from being freed
  76          */
  77         bio_get(bio);
  78
  79         ret = blk_rq_append_bio(rq, bio);
  80         if (ret) {
  81                 bio_endio(bio);
  82                 __blk_rq_unmap_user(orig_bio);
  83                 bio_put(bio);
  84                 return ret;
  85         }
  86
  87         return 0;
  88 }
  89
  90 /**
  91  * blk_rq_map_user_iov - map user data to a request, for REQ_TYPE_BLOCK_PC usage
  92  * @q:          request queue where request should be inserted
  93  * @rq:         request to map data to
  94  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
  95  * @iter:       iovec iterator
  96  * @gfp_mask:   memory allocation flags
  97  *
  98  * Description:
  99  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 100  *    a kernel bounce buffer is used.
 101  *
 102  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 103  *    still in process context.
 104  *
 105  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 106  *    before being submitted to the device, as pages mapped may be out of
 107  *    reach. It's the callers responsibility to make sure this happens. The
 108  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 109  *    unmapping.
 110  */
 111 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 112                         struct rq_map_data *map_data,
 113                         const struct iov_iter *iter, gfp_t gfp_mask)
 114 {
 115         bool copy = false;
 116         unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 117         struct bio *bio = NULL;
 118         struct iov_iter i;
 119         int ret;
 120
 121         if (map_data)
 122                 copy = true;
 123         else if (iov_iter_alignment(iter) & align)
 124                 copy = true;
 125         else if (queue_virt_boundary(q))
 126                 copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 127
 128         i = *iter;
 129         do {
 130                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 131                 if (ret)
 132                         goto unmap_rq;
 133                 if (!bio)
 134                         bio = rq->bio;
 135         } while (iov_iter_count(&i));
 136
 137         if (!bio_flagged(bio, BIO_USER_MAPPED))
 138                 rq->cmd_flags |= REQ_COPY_USER;
 139         return 0;
 140
 141 unmap_rq:
 142         __blk_rq_unmap_user(bio);
 143         rq->bio = NULL;
 144         return -EINVAL;
 145 }
 146 EXPORT_SYMBOL(blk_rq_map_user_iov);
 147
 148 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 149                     struct rq_map_data *map_data, void __user *ubuf,
 150                     unsigned long len, gfp_t gfp_mask)
 151 {
 152         struct iovec iov;
 153         struct iov_iter i;
 154         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 155
 156         if (unlikely(ret < 0))
 157                 return ret;
 158
 159         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 160 }
 161 EXPORT_SYMBOL(blk_rq_map_user);
 162
 163 /**
 164  * blk_rq_unmap_user - unmap a request with user data
 165  * @bio:               start of bio list
 166  *
 167  * Description:
 168  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 169  *    supply the original rq->bio from the blk_rq_map_user() return, since
 170  *    the I/O completion may have changed rq->bio.
 171  */
 172 int blk_rq_unmap_user(struct bio *bio)
 173 {
 174         struct bio *mapped_bio;
 175         int ret = 0, ret2;
 176
 177         while (bio) {
 178                 mapped_bio = bio;
 179                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 180                         mapped_bio = bio->bi_private;
 181
 182                 ret2 = __blk_rq_unmap_user(mapped_bio);
 183                 if (ret2 && !ret)
 184                         ret = ret2;
 185
 186                 mapped_bio = bio;
 187                 bio = bio->bi_next;
 188                 bio_put(mapped_bio);
 189         }
 190
 191         return ret;
 192 }
 193 EXPORT_SYMBOL(blk_rq_unmap_user);
 194
 195 /**
 196  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 197  * @q:          request queue where request should be inserted
 198  * @rq:         request to fill
 199  * @kbuf:       the kernel buffer
 200  * @len:        length of user data
 201  * @gfp_mask:   memory allocation flags
 202  *
 203  * Description:
 204  *    Data will be mapped directly if possible. Otherwise a bounce
 205  *    buffer is used. Can be called multiple times to append multiple
 206  *    buffers.
 207  */
 208 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 209                     unsigned int len, gfp_t gfp_mask)
 210 {
 211         int reading = rq_data_dir(rq) == READ;
 212         unsigned long addr = (unsigned long) kbuf;
 213         int do_copy = 0;
 214         struct bio *bio;
 215         int ret;
 216
 217         if (len > (queue_max_hw_sectors(q) << 9))
 218                 return -EINVAL;
 219         if (!len || !kbuf)
 220                 return -EINVAL;
 221
 222         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 223         if (do_copy)
 224                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 225         else
 226                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 227
 228         if (IS_ERR(bio))
 229                 return PTR_ERR(bio);
 230
 231         if (!reading)
 232                 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 233
 234         if (do_copy)
 235                 rq->cmd_flags |= REQ_COPY_USER;
 236
 237         ret = blk_rq_append_bio(rq, bio);
 238         if (unlikely(ret)) {
 239                 /* request is too big */
 240                 bio_put(bio);
 241                 return ret;
 242         }
 243
 244         blk_queue_bounce(q, &rq->bio);
 245         return 0;
 246 }
 247 EXPORT_SYMBOL(blk_rq_map_kern);