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