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authorKent Overstreet2014-02-07 14:53:46 -0600
committerJens Axboe2014-02-07 14:54:08 -0600
commit5cb8850c9c4a7605f74f5c9c7ecadd0b02e87a25 (patch)
tree401b42c4f5898a54c11c36da7ac37a14479bfffe /block
parent087787959ce851d7bbb19f10f6e9241b7f85a3ca (diff)
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block: Explicitly handle discard/write same segments
Immutable biovecs changed the way biovecs are interpreted - drivers no longer use bi_vcnt, they have to go by bi_iter.bi_size (to allow for using part of an existing segment without modifying it). This breaks with discards and write_same bios, since for those bi_size has nothing to do with segments in the biovec. So for now, we need a fairly gross hack - we fortunately know that there will never be more than one segment for the entire request, so we can special case discard/write_same. Signed-off-by: Kent Overstreet <kmo@daterainc.com> Tested-by: Hugh Dickins <hughd@google.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-merge.c91
1 files changed, 62 insertions, 29 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 8f8adaa95466..6c583f9c5b65 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -21,6 +21,16 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
21 if (!bio) 21 if (!bio)
22 return 0; 22 return 0;
23 23
24 /*
25 * This should probably be returning 0, but blk_add_request_payload()
26 * (Christoph!!!!)
27 */
28 if (bio->bi_rw & REQ_DISCARD)
29 return 1;
30
31 if (bio->bi_rw & REQ_WRITE_SAME)
32 return 1;
33
24 fbio = bio; 34 fbio = bio;
25 cluster = blk_queue_cluster(q); 35 cluster = blk_queue_cluster(q);
26 seg_size = 0; 36 seg_size = 0;
@@ -161,30 +171,60 @@ new_segment:
161 *bvprv = *bvec; 171 *bvprv = *bvec;
162} 172}
163 173
164/* 174static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
165 * map a request to scatterlist, return number of sg entries setup. Caller 175 struct scatterlist *sglist,
166 * must make sure sg can hold rq->nr_phys_segments entries 176 struct scatterlist **sg)
167 */
168int blk_rq_map_sg(struct request_queue *q, struct request *rq,
169 struct scatterlist *sglist)
170{ 177{
171 struct bio_vec bvec, bvprv = { NULL }; 178 struct bio_vec bvec, bvprv = { NULL };
172 struct req_iterator iter; 179 struct bvec_iter iter;
173 struct scatterlist *sg;
174 int nsegs, cluster; 180 int nsegs, cluster;
175 181
176 nsegs = 0; 182 nsegs = 0;
177 cluster = blk_queue_cluster(q); 183 cluster = blk_queue_cluster(q);
178 184
179 /* 185 if (bio->bi_rw & REQ_DISCARD) {
180 * for each bio in rq 186 /*
181 */ 187 * This is a hack - drivers should be neither modifying the
182 sg = NULL; 188 * biovec, nor relying on bi_vcnt - but because of
183 rq_for_each_segment(bvec, rq, iter) { 189 * blk_add_request_payload(), a discard bio may or may not have
184 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, &sg, 190 * a payload we need to set up here (thank you Christoph) and
185 &nsegs, &cluster); 191 * bi_vcnt is really the only way of telling if we need to.
186 } /* segments in rq */ 192 */
193
194 if (bio->bi_vcnt)
195 goto single_segment;
196
197 return 0;
198 }
199
200 if (bio->bi_rw & REQ_WRITE_SAME) {
201single_segment:
202 *sg = sglist;
203 bvec = bio_iovec(bio);
204 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
205 return 1;
206 }
207
208 for_each_bio(bio)
209 bio_for_each_segment(bvec, bio, iter)
210 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
211 &nsegs, &cluster);
187 212
213 return nsegs;
214}
215
216/*
217 * map a request to scatterlist, return number of sg entries setup. Caller
218 * must make sure sg can hold rq->nr_phys_segments entries
219 */
220int blk_rq_map_sg(struct request_queue *q, struct request *rq,
221 struct scatterlist *sglist)
222{
223 struct scatterlist *sg = NULL;
224 int nsegs = 0;
225
226 if (rq->bio)
227 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
188 228
189 if (unlikely(rq->cmd_flags & REQ_COPY_USER) && 229 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
190 (blk_rq_bytes(rq) & q->dma_pad_mask)) { 230 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
@@ -230,20 +270,13 @@ EXPORT_SYMBOL(blk_rq_map_sg);
230int blk_bio_map_sg(struct request_queue *q, struct bio *bio, 270int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
231 struct scatterlist *sglist) 271 struct scatterlist *sglist)
232{ 272{
233 struct bio_vec bvec, bvprv = { NULL }; 273 struct scatterlist *sg = NULL;
234 struct scatterlist *sg; 274 int nsegs;
235 int nsegs, cluster; 275 struct bio *next = bio->bi_next;
236 struct bvec_iter iter; 276 bio->bi_next = NULL;
237
238 nsegs = 0;
239 cluster = blk_queue_cluster(q);
240
241 sg = NULL;
242 bio_for_each_segment(bvec, bio, iter) {
243 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, &sg,
244 &nsegs, &cluster);
245 } /* segments in bio */
246 277
278 nsegs = __blk_bios_map_sg(q, bio, sglist, &sg);
279 bio->bi_next = next;
247 if (sg) 280 if (sg)
248 sg_mark_end(sg); 281 sg_mark_end(sg);
249 282