linux内核源码阅读之facebook硬盘加速flashcache之六
其实到目前为止，如果对读流程已经能轻松地看懂了，那么写流程不需要太多脑细胞。我觉得再写下去没有太大的必要了，后面想想为了保持flashcache完整性，还是写出来吧。接着到写流程：
1411static void1412flashcache_write_miss(struct cache_c *dmc, struct bio *bio, int index)1413{1414 struct cacheblock *cacheblk;1415 struct kcached_job *job;1416 int queued;14171418 cacheblk = &dmc->cache[index];1419 queued = flashcache_inval_blocks(dmc, bio);1420 if (queued) {1421 if (unlikely(queued < 0))1422 flashcache_bio_endio(bio, -EIO);1423 spin_unlock_irq(&dmc->cache_spin_lock);1424 return;1425 }1426 if (cacheblk->cache_state & VALID)1427 dmc->wr_replace++;1428 else1429 dmc->cached_blocks++;1430 cacheblk->cache_state = VALID | CACHEWRITEINPROG;1431 cacheblk->dbn = bio->bi_sector;1432 spin_unlock_irq(&dmc->cache_spin_lock);1433 job = new_kcached_job(dmc, bio, index);1434 if (unlikely(sysctl_flashcache_error_inject & WRITE_MISS_JOB_ALLOC_FAIL)) {1435 if (job)1436 flashcache_free_cache_job(job);1437 job = NULL;1438 sysctl_flashcache_error_inject &= ~WRITE_MISS_JOB_ALLOC_FAIL;1439 }1440 if (unlikely(job == NULL)) {1441 /* 1442 * We have a write miss, and can't allocate a job.1443 * Since we dropped the spinlock, we have to drain any 1444 * pending jobs.1445 */1446 DMERR("flashcache: Write (miss) failed ! Can't allocate memory for cache IO, block %lu", 1447 cacheblk->dbn);1448 flashcache_bio_endio(bio, -EIO);1449 spin_lock_irq(&dmc->cache_spin_lock);1450 dmc->cached_blocks--;1451 cacheblk->cache_state &= ~VALID;1452 cacheblk->cache_state |= INVALID;1453 flashcache_free_pending_jobs(dmc, cacheblk, -EIO);1454 cacheblk->cache_state &= ~(BLOCK_IO_INPROG);1455 spin_unlock_irq(&dmc->cache_spin_lock);1456 } else {1457 job->action = WRITECACHE; 1458 atomic_inc(&dmc->nr_jobs);1459 dmc->ssd_writes++;1460 dm_io_async_bvec(1, &job->cache, WRITE, 1461 bio->bi_io_vec + bio->bi_idx,1462 flashcache_io_callback, job);1463 flashcache_unplug_device(dmc->cache_dev->bdev);1464 flashcache_clean_set(dmc, index / dmc->assoc);1465 }1466}