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Linux/block/blk-map.c

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  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);
261 

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