block/blk-map.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Functions related to mapping data to requests
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/sched/task_stack.h>
   7 #include <linux/module.h>
   8 #include <linux/bio.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/uio.h>
  11
  12 #include "blk.h"
  13
  14 /*
  15  * Append a bio to a passthrough request.  Only works if the bio can be merged
  16  * into the request based on the driver constraints.
  17  */
  18 int blk_rq_append_bio(struct request *rq, struct bio **bio)
  19 {
  20         struct bio *orig_bio = *bio;
  21         struct bvec_iter iter;
  22         struct bio_vec bv;
  23         unsigned int nr_segs = 0;
  24
  25         blk_queue_bounce(rq->q, bio);
  26
  27         bio_for_each_bvec(bv, *bio, iter)
  28                 nr_segs++;
  29
  30         if (!rq->bio) {
  31                 blk_rq_bio_prep(rq, *bio, nr_segs);
  32         } else {
  33                 if (!ll_back_merge_fn(rq, *bio, nr_segs)) {
  34                         if (orig_bio != *bio) {
  35                                 bio_put(*bio);
  36                                 *bio = orig_bio;
  37                         }
  38                         return -EINVAL;
  39                 }
  40
  41                 rq->biotail->bi_next = *bio;
  42                 rq->biotail = *bio;
  43                 rq->__data_len += (*bio)->bi_iter.bi_size;
  44         }
  45
  46         return 0;
  47 }
  48 EXPORT_SYMBOL(blk_rq_append_bio);
  49
  50 static int __blk_rq_unmap_user(struct bio *bio)
  51 {
  52         int ret = 0;
  53
  54         if (bio) {
  55                 if (bio_flagged(bio, BIO_USER_MAPPED))
  56                         bio_unmap_user(bio);
  57                 else
  58                         ret = bio_uncopy_user(bio);
  59         }
  60
  61         return ret;
  62 }
  63
  64 static int __blk_rq_map_user_iov(struct request *rq,
  65                 struct rq_map_data *map_data, struct iov_iter *iter,
  66                 gfp_t gfp_mask, bool copy)
  67 {
  68         struct request_queue *q = rq->q;
  69         struct bio *bio, *orig_bio;
  70         int ret;
  71
  72         if (copy)
  73                 bio = bio_copy_user_iov(q, map_data, iter, gfp_mask);
  74         else
  75                 bio = bio_map_user_iov(q, iter, gfp_mask);
  76
  77         if (IS_ERR(bio))
  78                 return PTR_ERR(bio);
  79
  80         bio->bi_opf &= ~REQ_OP_MASK;
  81         bio->bi_opf |= req_op(rq);
  82
  83         orig_bio = bio;
  84
  85         /*
  86          * We link the bounce buffer in and could have to traverse it
  87          * later so we have to get a ref to prevent it from being freed
  88          */
  89         ret = blk_rq_append_bio(rq, &bio);
  90         if (ret) {
  91                 __blk_rq_unmap_user(orig_bio);
  92                 return ret;
  93         }
  94         bio_get(bio);
  95
  96         return 0;
  97 }
  98
  99 /**
 100  * blk_rq_map_user_iov - map user data to a request, for passthrough requests
 101  * @q:          request queue where request should be inserted
 102  * @rq:         request to map data to
 103  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
 104  * @iter:       iovec iterator
 105  * @gfp_mask:   memory allocation flags
 106  *
 107  * Description:
 108  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 109  *    a kernel bounce buffer is used.
 110  *
 111  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 112  *    still in process context.
 113  *
 114  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 115  *    before being submitted to the device, as pages mapped may be out of
 116  *    reach. It's the callers responsibility to make sure this happens. The
 117  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 118  *    unmapping.
 119  */
 120 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 121                         struct rq_map_data *map_data,
 122                         const struct iov_iter *iter, gfp_t gfp_mask)
 123 {
 124         bool copy = false;
 125         unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 126         struct bio *bio = NULL;
 127         struct iov_iter i;
 128         int ret = -EINVAL;
 129
 130         if (!iter_is_iovec(iter))
 131                 goto fail;
 132
 133         if (map_data)
 134                 copy = true;
 135         else if (iov_iter_alignment(iter) & align)
 136                 copy = true;
 137         else if (queue_virt_boundary(q))
 138                 copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 139
 140         i = *iter;
 141         do {
 142                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 143                 if (ret)
 144                         goto unmap_rq;
 145                 if (!bio)
 146                         bio = rq->bio;
 147         } while (iov_iter_count(&i));
 148
 149         if (!bio_flagged(bio, BIO_USER_MAPPED))
 150                 rq->rq_flags |= RQF_COPY_USER;
 151         return 0;
 152
 153 unmap_rq:
 154         blk_rq_unmap_user(bio);
 155 fail:
 156         rq->bio = NULL;
 157         return ret;
 158 }
 159 EXPORT_SYMBOL(blk_rq_map_user_iov);
 160
 161 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 162                     struct rq_map_data *map_data, void __user *ubuf,
 163                     unsigned long len, gfp_t gfp_mask)
 164 {
 165         struct iovec iov;
 166         struct iov_iter i;
 167         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 168
 169         if (unlikely(ret < 0))
 170                 return ret;
 171
 172         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 173 }
 174 EXPORT_SYMBOL(blk_rq_map_user);
 175
 176 /**
 177  * blk_rq_unmap_user - unmap a request with user data
 178  * @bio:               start of bio list
 179  *
 180  * Description:
 181  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 182  *    supply the original rq->bio from the blk_rq_map_user() return, since
 183  *    the I/O completion may have changed rq->bio.
 184  */
 185 int blk_rq_unmap_user(struct bio *bio)
 186 {
 187         struct bio *mapped_bio;
 188         int ret = 0, ret2;
 189
 190         while (bio) {
 191                 mapped_bio = bio;
 192                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 193                         mapped_bio = bio->bi_private;
 194
 195                 ret2 = __blk_rq_unmap_user(mapped_bio);
 196                 if (ret2 && !ret)
 197                         ret = ret2;
 198
 199                 mapped_bio = bio;
 200                 bio = bio->bi_next;
 201                 bio_put(mapped_bio);
 202         }
 203
 204         return ret;
 205 }
 206 EXPORT_SYMBOL(blk_rq_unmap_user);
 207
 208 /**
 209  * blk_rq_map_kern - map kernel data to a request, for passthrough requests
 210  * @q:          request queue where request should be inserted
 211  * @rq:         request to fill
 212  * @kbuf:       the kernel buffer
 213  * @len:        length of user data
 214  * @gfp_mask:   memory allocation flags
 215  *
 216  * Description:
 217  *    Data will be mapped directly if possible. Otherwise a bounce
 218  *    buffer is used. Can be called multiple times to append multiple
 219  *    buffers.
 220  */
 221 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 222                     unsigned int len, gfp_t gfp_mask)
 223 {
 224         int reading = rq_data_dir(rq) == READ;
 225         unsigned long addr = (unsigned long) kbuf;
 226         int do_copy = 0;
 227         struct bio *bio, *orig_bio;
 228         int ret;
 229
 230         if (len > (queue_max_hw_sectors(q) << 9))
 231                 return -EINVAL;
 232         if (!len || !kbuf)
 233                 return -EINVAL;
 234
 235         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 236         if (do_copy)
 237                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 238         else
 239                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 240
 241         if (IS_ERR(bio))
 242                 return PTR_ERR(bio);
 243
 244         bio->bi_opf &= ~REQ_OP_MASK;
 245         bio->bi_opf |= req_op(rq);
 246
 247         if (do_copy)
 248                 rq->rq_flags |= RQF_COPY_USER;
 249
 250         orig_bio = bio;
 251         ret = blk_rq_append_bio(rq, &bio);
 252         if (unlikely(ret)) {
 253                 /* request is too big */
 254                 bio_put(orig_bio);
 255                 return ret;
 256         }
 257
 258         return 0;
 259 }
 260 EXPORT_SYMBOL(blk_rq_map_kern);