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         if (map_data && map_data->null_mapped)
  78                 bio_set_flag(bio, BIO_NULL_MAPPED);
  79
  80         iov_iter_advance(iter, bio->bi_iter.bi_size);
  81         if (map_data)
  82                 map_data->offset += bio->bi_iter.bi_size;
  83
  84         orig_bio = bio;
  85
  86         /*
  87          * We link the bounce buffer in and could have to traverse it
  88          * later so we have to get a ref to prevent it from being freed
  89          */
  90         ret = blk_rq_append_bio(rq, &bio);
  91         if (ret) {
  92                 __blk_rq_unmap_user(orig_bio);
  93                 return ret;
  94         }
  95         bio_get(bio);
  96
  97         return 0;
  98 }
  99
 100 /**
 101  * blk_rq_map_user_iov - map user data to a request, for passthrough requests
 102  * @q:          request queue where request should be inserted
 103  * @rq:         request to map data to
 104  * @map_data:   pointer to the rq_map_data holding pages (if necessary)
 105  * @iter:       iovec iterator
 106  * @gfp_mask:   memory allocation flags
 107  *
 108  * Description:
 109  *    Data will be mapped directly for zero copy I/O, if possible. Otherwise
 110  *    a kernel bounce buffer is used.
 111  *
 112  *    A matching blk_rq_unmap_user() must be issued at the end of I/O, while
 113  *    still in process context.
 114  *
 115  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
 116  *    before being submitted to the device, as pages mapped may be out of
 117  *    reach. It's the callers responsibility to make sure this happens. The
 118  *    original bio must be passed back in to blk_rq_unmap_user() for proper
 119  *    unmapping.
 120  */
 121 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
 122                         struct rq_map_data *map_data,
 123                         const struct iov_iter *iter, gfp_t gfp_mask)
 124 {
 125         bool copy = false;
 126         unsigned long align = q->dma_pad_mask | queue_dma_alignment(q);
 127         struct bio *bio = NULL;
 128         struct iov_iter i;
 129         int ret = -EINVAL;
 130
 131         if (!iter_is_iovec(iter))
 132                 goto fail;
 133
 134         if (map_data)
 135                 copy = true;
 136         else if (iov_iter_alignment(iter) & align)
 137                 copy = true;
 138         else if (queue_virt_boundary(q))
 139                 copy = queue_virt_boundary(q) & iov_iter_gap_alignment(iter);
 140
 141         i = *iter;
 142         do {
 143                 ret =__blk_rq_map_user_iov(rq, map_data, &i, gfp_mask, copy);
 144                 if (ret)
 145                         goto unmap_rq;
 146                 if (!bio)
 147                         bio = rq->bio;
 148         } while (iov_iter_count(&i));
 149
 150         if (!bio_flagged(bio, BIO_USER_MAPPED))
 151                 rq->rq_flags |= RQF_COPY_USER;
 152         return 0;
 153
 154 unmap_rq:
 155         blk_rq_unmap_user(bio);
 156 fail:
 157         rq->bio = NULL;
 158         return ret;
 159 }
 160 EXPORT_SYMBOL(blk_rq_map_user_iov);
 161
 162 int blk_rq_map_user(struct request_queue *q, struct request *rq,
 163                     struct rq_map_data *map_data, void __user *ubuf,
 164                     unsigned long len, gfp_t gfp_mask)
 165 {
 166         struct iovec iov;
 167         struct iov_iter i;
 168         int ret = import_single_range(rq_data_dir(rq), ubuf, len, &iov, &i);
 169
 170         if (unlikely(ret < 0))
 171                 return ret;
 172
 173         return blk_rq_map_user_iov(q, rq, map_data, &i, gfp_mask);
 174 }
 175 EXPORT_SYMBOL(blk_rq_map_user);
 176
 177 /**
 178  * blk_rq_unmap_user - unmap a request with user data
 179  * @bio:               start of bio list
 180  *
 181  * Description:
 182  *    Unmap a rq previously mapped by blk_rq_map_user(). The caller must
 183  *    supply the original rq->bio from the blk_rq_map_user() return, since
 184  *    the I/O completion may have changed rq->bio.
 185  */
 186 int blk_rq_unmap_user(struct bio *bio)
 187 {
 188         struct bio *mapped_bio;
 189         int ret = 0, ret2;
 190
 191         while (bio) {
 192                 mapped_bio = bio;
 193                 if (unlikely(bio_flagged(bio, BIO_BOUNCED)))
 194                         mapped_bio = bio->bi_private;
 195
 196                 ret2 = __blk_rq_unmap_user(mapped_bio);
 197                 if (ret2 && !ret)
 198                         ret = ret2;
 199
 200                 mapped_bio = bio;
 201                 bio = bio->bi_next;
 202                 bio_put(mapped_bio);
 203         }
 204
 205         return ret;
 206 }
 207 EXPORT_SYMBOL(blk_rq_unmap_user);
 208
 209 /**
 210  * blk_rq_map_kern - map kernel data to a request, for passthrough requests
 211  * @q:          request queue where request should be inserted
 212  * @rq:         request to fill
 213  * @kbuf:       the kernel buffer
 214  * @len:        length of user data
 215  * @gfp_mask:   memory allocation flags
 216  *
 217  * Description:
 218  *    Data will be mapped directly if possible. Otherwise a bounce
 219  *    buffer is used. Can be called multiple times to append multiple
 220  *    buffers.
 221  */
 222 int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
 223                     unsigned int len, gfp_t gfp_mask)
 224 {
 225         int reading = rq_data_dir(rq) == READ;
 226         unsigned long addr = (unsigned long) kbuf;
 227         int do_copy = 0;
 228         struct bio *bio, *orig_bio;
 229         int ret;
 230
 231         if (len > (queue_max_hw_sectors(q) << 9))
 232                 return -EINVAL;
 233         if (!len || !kbuf)
 234                 return -EINVAL;
 235
 236         do_copy = !blk_rq_aligned(q, addr, len) || object_is_on_stack(kbuf);
 237         if (do_copy)
 238                 bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
 239         else
 240                 bio = bio_map_kern(q, kbuf, len, gfp_mask);
 241
 242         if (IS_ERR(bio))
 243                 return PTR_ERR(bio);
 244
 245         bio->bi_opf &= ~REQ_OP_MASK;
 246         bio->bi_opf |= req_op(rq);
 247
 248         if (do_copy)
 249                 rq->rq_flags |= RQF_COPY_USER;
 250
 251         orig_bio = bio;
 252         ret = blk_rq_append_bio(rq, &bio);
 253         if (unlikely(ret)) {
 254                 /* request is too big */
 255                 bio_put(orig_bio);
 256                 return ret;
 257         }
 258
 259         return 0;
 260 }
 261 EXPORT_SYMBOL(blk_rq_map_kern);