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 (!iter_is_iovec(iter))
 122                 goto fail;
 123
 124         if (map_data)
 125                 copy = true;
 126         else if (iov_iter_alignment(iter) & align)
 127                 copy = true;
 128         else if (queue_virt_boundary(q))
 129                 copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 130
 131         i = *iter;
 132         do {
 133                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 134                 if (ret)
 135                         goto unmap_rq;
 136                 if (!bio)
 137                         bio = rq->bio;
 138         } while (iov_iter_count(&i));
 139
 140         if (!bio_flagged(bio, BIO_USER_MAPPED))
 141                 rq->cmd_flags |= REQ_COPY_USER;
 142         return 0;
 143
 144 unmap_rq:
 145         __blk_rq_unmap_user(bio);
 146 fail:
 147         rq->bio = NULL;
 148         return -EINVAL;
 149 }
 150 EXPORT_SYMBOL(blk_rq_map_user_iov);
 151
 152 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 153                     struct rq_map_data *map_data, void __user *ubuf,
 154                     unsigned long len, gfp_t gfp_mask)
 155 {
 156         struct iovec iov;
 157         struct iov_iter i;
 158         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 159
 160         if (unlikely(ret < 0))
 161                 return ret;
 162
 163         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 164 }
 165 EXPORT_SYMBOL(blk_rq_map_user);
 166
 167 /**
 168  * blk_rq_unmap_user - unmap a request with user data
 169  * @bio:               start of bio list
 170  *
 171  * Description:
 172  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 173  *    supply the original rq->bio from the blk_rq_map_user() return, since
 174  *    the I/O completion may have changed rq->bio.
 175  */
 176 int blk_rq_unmap_user(struct bio *bio)
 177 {
 178         struct bio *mapped_bio;
 179         int ret = 0, ret2;
 180
 181         while (bio) {
 182                 mapped_bio = bio;
 183                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 184                         mapped_bio = bio->bi_private;
 185
 186                 ret2 = __blk_rq_unmap_user(mapped_bio);
 187                 if (ret2 && !ret)
 188                         ret = ret2;
 189
 190                 mapped_bio = bio;
 191                 bio = bio->bi_next;
 192                 bio_put(mapped_bio);
 193         }
 194
 195         return ret;
 196 }
 197 EXPORT_SYMBOL(blk_rq_unmap_user);
 198
 199 /**
 200  * blk_rq_map_kern - map kernel data to a request, for REQ_TYPE_BLOCK_PC usage
 201  * @q:          request queue where request should be inserted
 202  * @rq:         request to fill
 203  * @kbuf:       the kernel buffer
 204  * @len:        length of user data
 205  * @gfp_mask:   memory allocation flags
 206  *
 207  * Description:
 208  *    Data will be mapped directly if possible. Otherwise a bounce
 209  *    buffer is used. Can be called multiple times to append multiple
 210  *    buffers.
 211  */
 212 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 213                     unsigned int len, gfp_t gfp_mask)
 214 {
 215         int reading = rq_data_dir(rq) == READ;
 216         unsigned long addr = (unsigned long) kbuf;
 217         int do_copy = 0;
 218         struct bio *bio;
 219         int ret;
 220
 221         if (len > (queue_max_hw_sectors(q) << 9))
 222                 return -EINVAL;
 223         if (!len || !kbuf)
 224                 return -EINVAL;
 225
 226         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 227         if (do_copy)
 228                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 229         else
 230                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 231
 232         if (IS_ERR(bio))
 233                 return PTR_ERR(bio);
 234
 235         if (!reading)
 236                 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 237
 238         if (do_copy)
 239                 rq->cmd_flags |= REQ_COPY_USER;
 240
 241         ret = blk_rq_append_bio(rq, bio);
 242         if (unlikely(ret)) {
 243                 /* request is too big */
 244                 bio_put(bio);
 245                 return ret;
 246         }
 247
 248         blk_queue_bounce(q, &rq->bio);
 249         return 0;
 250 }
 251 EXPORT_SYMBOL(blk_rq_map_kern);