For filesystems with a blocksize < page size, we can merge same page calls into the bio_vec at the end of the bio. This saves segments on systems with a page size > the "normal" 4kb fs block size.
Unified · Split
| @@ -325,10 +325,31 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page · 324 unmodified lines | |||
| 325 | if (unlikely(bio_flagged(bio, BIO_CLONED))) | 325 | if (unlikely(bio_flagged(bio, BIO_CLONED))) |
| 326 | return 0; | 326 | return 0; |
| 327 | 327 | ||
| 328 | if (bio->bi_vcnt >= bio->bi_max_vecs) | 328 | if (((bio->bi_size + len) >> 9) > max_sectors) |
| 329 | return 0; | 329 | return 0; |
| 330 | 330 | ||
| 331 | if (((bio->bi_size + len) >> 9) > max_sectors) | 331 | /* |
| 332 | * For filesystems with a blocksize smaller than the pagesize | ||
| 333 | * we will often be called with the same page as last time and | ||
| 334 | * a consecutive offset. Optimize this special case. | ||
| 335 | */ | ||
| 336 | if (bio->bi_vcnt > 0) { | ||
| 337 | struct bio_vec *prev = &bio->bi_io_vec[bio->bi_vcnt - 1]; | ||
| 338 | |||
| 339 | if (page == prev->bv_page && | ||
| 340 | offset == prev->bv_offset + prev->bv_len) { | ||
| 341 | prev->bv_len += len; | ||
| 342 | if (q->merge_bvec_fn && | ||
| 343 | q->merge_bvec_fn(q, bio, prev) < len) { | ||
| 344 | prev->bv_len -= len; | ||
| 345 | return 0; | ||
| 346 | } | ||
| 347 | |||
| 348 | goto done; | ||
| 349 | } | ||
| 350 | } | ||
| 351 | |||
| 352 | if (bio->bi_vcnt >= bio->bi_max_vecs) | ||
| 332 | return 0; | 353 | return 0; |
| 333 | 354 | ||
| 334 | /* | 355 | /* |
| @@ -382,6 +403,7 @@ static int __bio_add_page(request_queue_t *q, struct bio *bio, struct page · 47 unmodified lines | |||
| 382 | bio->bi_vcnt++; | 403 | bio->bi_vcnt++; |
| 383 | bio->bi_phys_segments++; | 404 | bio->bi_phys_segments++; |
| 384 | bio->bi_hw_segments++; | 405 | bio->bi_hw_segments++; |
| 406 | done: | ||
| 385 | bio->bi_size += len; | 407 | bio->bi_size += len; |
| 386 | return len; | 408 | return len; |
| 387 | } | 409 | } |