> On 15 Mar 2019, at 02.52, Igor Konopko wrote: > > > > On 14.03.2019 22:35, Heiner Litz wrote: >> On Thu, Mar 14, 2019 at 9:07 AM Igor Konopko wrote: >>> This patch changes the approach to handling partial read path. >>> >>> In old approach merging of data from round buffer and drive was fully >>> made by drive. This had some disadvantages - code was complex and >>> relies on bio internals, so it was hard to maintain and was strongly >>> dependent on bio changes. >>> >>> In new approach most of the handling is done mostly by block layer >>> functions such as bio_split(), bio_chain() and generic_make request() >>> and generally is less complex and easier to maintain. Below some more >>> details of the new approach. >>> >>> When read bio arrives, it is cloned for pblk internal purposes. All >>> the L2P mapping, which includes copying data from round buffer to bio >>> and thus bio_advance() calls is done on the cloned bio, so the original >>> bio is untouched. Later if we found that we have partial read case, we >>> still have original bio untouched, so we can split it and continue to >>> process only first 4K of it in current context, when the rest will be >>> called as separate bio request which is passed to generic_make_request() >>> for further processing. >>> >>> Signed-off-by: Igor Konopko >>> --- >>> drivers/lightnvm/pblk-read.c | 242 ++++++++----------------------------------- >>> drivers/lightnvm/pblk.h | 12 --- >>> 2 files changed, 41 insertions(+), 213 deletions(-) >>> >>> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c >>> index 6569746..54422a2 100644 >>> --- a/drivers/lightnvm/pblk-read.c >>> +++ b/drivers/lightnvm/pblk-read.c >>> @@ -222,171 +222,6 @@ static void pblk_end_io_read(struct nvm_rq *rqd) >>> __pblk_end_io_read(pblk, rqd, true); >>> } >>> >>> -static void pblk_end_partial_read(struct nvm_rq *rqd) >>> -{ >>> - struct pblk *pblk = rqd->private; >>> - struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd); >>> - struct pblk_pr_ctx *pr_ctx = r_ctx->private; >>> - struct pblk_sec_meta *meta; >>> - struct bio *new_bio = rqd->bio; >>> - struct bio *bio = pr_ctx->orig_bio; >>> - struct bio_vec src_bv, dst_bv; >>> - void *meta_list = rqd->meta_list; >>> - int bio_init_idx = pr_ctx->bio_init_idx; >>> - unsigned long *read_bitmap = pr_ctx->bitmap; >>> - int nr_secs = pr_ctx->orig_nr_secs; >>> - int nr_holes = nr_secs - bitmap_weight(read_bitmap, nr_secs); >>> - void *src_p, *dst_p; >>> - int hole, i; >>> - >>> - if (unlikely(nr_holes == 1)) { >>> - struct ppa_addr ppa; >>> - >>> - ppa = rqd->ppa_addr; >>> - rqd->ppa_list = pr_ctx->ppa_ptr; >>> - rqd->dma_ppa_list = pr_ctx->dma_ppa_list; >>> - rqd->ppa_list[0] = ppa; >>> - } >>> - >>> - for (i = 0; i < nr_secs; i++) { >>> - meta = pblk_get_meta(pblk, meta_list, i); >>> - pr_ctx->lba_list_media[i] = le64_to_cpu(meta->lba); >>> - meta->lba = cpu_to_le64(pr_ctx->lba_list_mem[i]); >>> - } >>> - >>> - /* Fill the holes in the original bio */ >>> - i = 0; >>> - hole = find_first_zero_bit(read_bitmap, nr_secs); >>> - do { >>> - struct pblk_line *line; >>> - >>> - line = pblk_ppa_to_line(pblk, rqd->ppa_list[i]); >>> - kref_put(&line->ref, pblk_line_put); >>> - >>> - meta = pblk_get_meta(pblk, meta_list, hole); >>> - meta->lba = cpu_to_le64(pr_ctx->lba_list_media[i]); >>> - >>> - src_bv = new_bio->bi_io_vec[i++]; >>> - dst_bv = bio->bi_io_vec[bio_init_idx + hole]; >>> - >>> - src_p = kmap_atomic(src_bv.bv_page); >>> - dst_p = kmap_atomic(dst_bv.bv_page); >>> - >>> - memcpy(dst_p + dst_bv.bv_offset, >>> - src_p + src_bv.bv_offset, >>> - PBLK_EXPOSED_PAGE_SIZE); >>> - >>> - kunmap_atomic(src_p); >>> - kunmap_atomic(dst_p); >>> - >>> - mempool_free(src_bv.bv_page, &pblk->page_bio_pool); >>> - >>> - hole = find_next_zero_bit(read_bitmap, nr_secs, hole + 1); >>> - } while (hole < nr_secs); >>> - >>> - bio_put(new_bio); >>> - kfree(pr_ctx); >>> - >>> - /* restore original request */ >>> - rqd->bio = NULL; >>> - rqd->nr_ppas = nr_secs; >>> - >>> - pblk_end_user_read(bio, rqd->error); >>> - __pblk_end_io_read(pblk, rqd, false); >>> -} >>> - >>> -static int pblk_setup_partial_read(struct pblk *pblk, struct nvm_rq *rqd, >>> - unsigned int bio_init_idx, >>> - unsigned long *read_bitmap, >>> - int nr_holes) >>> -{ >>> - void *meta_list = rqd->meta_list; >>> - struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd); >>> - struct pblk_pr_ctx *pr_ctx; >>> - struct bio *new_bio, *bio = r_ctx->private; >>> - int nr_secs = rqd->nr_ppas; >>> - int i; >>> - >>> - new_bio = bio_alloc(GFP_KERNEL, nr_holes); >>> - >>> - if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes)) >>> - goto fail_bio_put; >>> - >>> - if (nr_holes != new_bio->bi_vcnt) { >>> - WARN_ONCE(1, "pblk: malformed bio\n"); >>> - goto fail_free_pages; >>> - } >>> - >>> - pr_ctx = kzalloc(sizeof(struct pblk_pr_ctx), GFP_KERNEL); >>> - if (!pr_ctx) >>> - goto fail_free_pages; >>> - >>> - for (i = 0; i < nr_secs; i++) { >>> - struct pblk_sec_meta *meta = pblk_get_meta(pblk, meta_list, i); >>> - >>> - pr_ctx->lba_list_mem[i] = le64_to_cpu(meta->lba); >>> - } >>> - >>> - new_bio->bi_iter.bi_sector = 0; /* internal bio */ >>> - bio_set_op_attrs(new_bio, REQ_OP_READ, 0); >>> - >>> - rqd->bio = new_bio; >>> - rqd->nr_ppas = nr_holes; >>> - >>> - pr_ctx->orig_bio = bio; >>> - bitmap_copy(pr_ctx->bitmap, read_bitmap, NVM_MAX_VLBA); >>> - pr_ctx->bio_init_idx = bio_init_idx; >>> - pr_ctx->orig_nr_secs = nr_secs; >>> - r_ctx->private = pr_ctx; >>> - >>> - if (unlikely(nr_holes == 1)) { >>> - pr_ctx->ppa_ptr = rqd->ppa_list; >>> - pr_ctx->dma_ppa_list = rqd->dma_ppa_list; >>> - rqd->ppa_addr = rqd->ppa_list[0]; >>> - } >>> - return 0; >>> - >>> -fail_free_pages: >>> - pblk_bio_free_pages(pblk, new_bio, 0, new_bio->bi_vcnt); >>> -fail_bio_put: >>> - bio_put(new_bio); >>> - >>> - return -ENOMEM; >>> -} >>> - >>> -static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd, >>> - unsigned int bio_init_idx, >>> - unsigned long *read_bitmap, int nr_secs) >>> -{ >>> - int nr_holes; >>> - int ret; >>> - >>> - nr_holes = nr_secs - bitmap_weight(read_bitmap, nr_secs); >>> - >>> - if (pblk_setup_partial_read(pblk, rqd, bio_init_idx, read_bitmap, >>> - nr_holes)) >>> - return NVM_IO_ERR; >>> - >>> - rqd->end_io = pblk_end_partial_read; >>> - >>> - ret = pblk_submit_io(pblk, rqd); >>> - if (ret) { >>> - bio_put(rqd->bio); >>> - pblk_err(pblk, "partial read IO submission failed\n"); >>> - goto err; >>> - } >>> - >>> - return NVM_IO_OK; >>> - >>> -err: >>> - pblk_err(pblk, "failed to perform partial read\n"); >>> - >>> - /* Free allocated pages in new bio */ >>> - pblk_bio_free_pages(pblk, rqd->bio, 0, rqd->bio->bi_vcnt); >>> - __pblk_end_io_read(pblk, rqd, false); >>> - return NVM_IO_ERR; >>> -} >>> - >>> static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio, >>> sector_t lba, unsigned long *read_bitmap) >>> { >>> @@ -432,11 +267,11 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio) >>> { >>> struct nvm_tgt_dev *dev = pblk->dev; >>> struct request_queue *q = dev->q; >>> + struct bio *split_bio, *int_bio; >>> sector_t blba = pblk_get_lba(bio); >>> unsigned int nr_secs = pblk_get_secs(bio); >>> struct pblk_g_ctx *r_ctx; >>> struct nvm_rq *rqd; >>> - unsigned int bio_init_idx; >>> DECLARE_BITMAP(read_bitmap, NVM_MAX_VLBA); >>> int ret = NVM_IO_ERR; >>> >>> @@ -456,61 +291,66 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio) >>> r_ctx = nvm_rq_to_pdu(rqd); >>> r_ctx->start_time = jiffies; >>> r_ctx->lba = blba; >>> - r_ctx->private = bio; /* original bio */ >>> >>> - /* Save the index for this bio's start. This is needed in case >>> - * we need to fill a partial read. >>> + /* Clone read bio to deal with: >>> + * -usage of bio_advance() when memcpy data from round buffer >>> + * -read errors in case of reading from device >>> */ >>> - bio_init_idx = pblk_get_bi_idx(bio); >>> + int_bio = bio_clone_fast(bio, GFP_KERNEL, &pblk_bio_set); >>> + if (!int_bio) >>> + return NVM_IO_ERR; >>> >>> if (pblk_alloc_rqd_meta(pblk, rqd)) >>> goto fail_rqd_free; >>> >>> if (nr_secs > 1) >>> - pblk_read_ppalist_rq(pblk, rqd, bio, blba, read_bitmap); >>> + pblk_read_ppalist_rq(pblk, rqd, int_bio, blba, read_bitmap); >>> else >>> - pblk_read_rq(pblk, rqd, bio, blba, read_bitmap); >>> + pblk_read_rq(pblk, rqd, int_bio, blba, read_bitmap); >>> + >>> +split_retry: >>> + r_ctx->private = bio; /* original bio */ >>> >>> - if (bitmap_full(read_bitmap, nr_secs)) { >>> + if (bitmap_full(read_bitmap, rqd->nr_ppas)) { >>> + bio_put(int_bio); >>> atomic_inc(&pblk->inflight_io); >>> __pblk_end_io_read(pblk, rqd, false); >>> return NVM_IO_DONE; >>> } >>> >>> - /* All sectors are to be read from the device */ >>> - if (bitmap_empty(read_bitmap, rqd->nr_ppas)) { >>> - struct bio *int_bio = NULL; >>> + if (!bitmap_empty(read_bitmap, rqd->nr_ppas)) { >>> + /* The read bio request could be partially filled by the write >>> + * buffer, but there are some holes that need to be read from >>> + * the drive. In order to handle this, we will use block layer >>> + * mechanism to split this request in to smaller ones. >>> + */ >>> + split_bio = bio_split(bio, NR_PHY_IN_LOG, GFP_KERNEL, >>> + &pblk_bio_set); >> This is quite inefficient. If you have an rqd with 63 sectors on the device and >> the 64th is cached, you are splitting 63 times whereas a single split >> would be sufficient. > > Yeah, definitely, it would be better to find how many contiguous sectors in cache/on drive are and splitting based on it. Will improve that in v2. > >>> + bio_chain(split_bio, bio); >> I am not sure if it's needed but in blk_queue_split() these flags are set >> before making the request: >> split->bi_opf |= REQ_NOMERGE; >> bio_set_flag(*bio, BIO_QUEUE_ENTERED); >>> + generic_make_request(bio); >> pblk_lookup_l2p_seq() increments line->ref. You have to release the krefs before >> requeing the request. > I completely forgot about it, will fix that of course, thanks! > >> You might consider introducing a pblk_lookup_l2p_uncached() which returns when >> it finds a cached sector and returns its index. Doing so you can avoid obtaining >> superfluous line->refs and we could also get rid of the read_bitmap >> entirely. This >> index could also be used to split the bio at the right position. I think you can also get rid of the read_bitmap. This would help removing one of the 64 lba dependencies in pblk, which I think is useful as we move forward.