[PATCH v3] lightnvm: pblk: add asynchronous partial read

[Heiner Litz <hlitz@ucsc.edu>]

In the read path, partial reads are currently performed synchronously
which affects performance for workloads that generate many partial
reads. This patch adds an asynchronous partial read path as well as
the required partial read ctx.

Signed-off-by: Heiner Litz <hlitz@ucsc.edu>

---

v3: rebase to head, incorporate 64-bit read bitmap

---
 drivers/lightnvm/pblk-read.c | 183 ++++++++++++++++++++++++++++---------------
 drivers/lightnvm/pblk.h      |  10 +++
 2 files changed, 130 insertions(+), 63 deletions(-)

diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
index 9c9362b..4a44076 100644
--- a/drivers/lightnvm/pblk-read.c
+++ b/drivers/lightnvm/pblk-read.c
@@ -231,74 +231,36 @@ static void pblk_end_io_read(struct nvm_rq *rqd)
 	__pblk_end_io_read(pblk, rqd, true);
 }
 
-static int pblk_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
-			     struct bio *orig_bio, unsigned int bio_init_idx,
-			     unsigned long *read_bitmap)
+static void pblk_end_partial_read(struct nvm_rq *rqd)
 {
-	struct pblk_sec_meta *meta_list = rqd->meta_list;
-	struct bio *new_bio;
+	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 bio *new_bio = rqd->bio;
+	struct bio *bio = pr_ctx->orig_bio;
 	struct bio_vec src_bv, dst_bv;
-	void *ppa_ptr = NULL;
-	void *src_p, *dst_p;
-	dma_addr_t dma_ppa_list = 0;
-	__le64 *lba_list_mem, *lba_list_media;
-	int nr_secs = rqd->nr_ppas;
+	struct pblk_sec_meta *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);
-	int i, ret, hole;
-
-	/* Re-use allocated memory for intermediate lbas */
-	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
-	lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk_dma_ppa_size);
-
-	new_bio = bio_alloc(GFP_KERNEL, nr_holes);
-
-	if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes))
-		goto fail_add_pages;
-
-	if (nr_holes != new_bio->bi_vcnt) {
-		pblk_err(pblk, "malformed bio\n");
-		goto fail;
-	}
-
-	for (i = 0; i < nr_secs; i++)
-		lba_list_mem[i] = meta_list[i].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;
-	rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);
-
-	if (unlikely(nr_holes == 1)) {
-		ppa_ptr = rqd->ppa_list;
-		dma_ppa_list = rqd->dma_ppa_list;
-		rqd->ppa_addr = rqd->ppa_list[0];
-	}
-
-	ret = pblk_submit_io_sync(pblk, rqd);
-	if (ret) {
-		bio_put(rqd->bio);
-		pblk_err(pblk, "sync read IO submission failed\n");
-		goto fail;
-	}
-
-	if (rqd->error) {
-		atomic_long_inc(&pblk->read_failed);
-#ifdef CONFIG_NVM_PBLK_DEBUG
-		pblk_print_failed_rqd(pblk, rqd, rqd->error);
-#endif
-	}
+	__le64 *lba_list_mem, *lba_list_media;
+	void *src_p, *dst_p;
+	int hole, i;
 
 	if (unlikely(nr_holes == 1)) {
 		struct ppa_addr ppa;
 
 		ppa = rqd->ppa_addr;
-		rqd->ppa_list = ppa_ptr;
-		rqd->dma_ppa_list = dma_ppa_list;
+		rqd->ppa_list = pr_ctx->ppa_ptr;
+		rqd->dma_ppa_list = pr_ctx->dma_ppa_list;
 		rqd->ppa_list[0] = ppa;
 	}
 
+	/* Re-use allocated memory for intermediate lbas */
+	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
+	lba_list_media = (((void *)rqd->ppa_list) + 2 * pblk_dma_ppa_size);
+
 	for (i = 0; i < nr_secs; i++) {
 		lba_list_media[i] = meta_list[i].lba;
 		meta_list[i].lba = lba_list_mem[i];
@@ -316,7 +278,7 @@ static int pblk_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
 		meta_list[hole].lba = lba_list_media[i];
 
 		src_bv = new_bio->bi_io_vec[i++];
-		dst_bv = orig_bio->bi_io_vec[bio_init_idx + hole];
+		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);
@@ -334,19 +296,107 @@ static int pblk_partial_read(struct pblk *pblk, struct nvm_rq *rqd,
 	} while (hole < nr_secs);
 
 	bio_put(new_bio);
+	kfree(pr_ctx);
 
 	/* restore original request */
 	rqd->bio = NULL;
 	rqd->nr_ppas = nr_secs;
 
+	bio_endio(bio);
 	__pblk_end_io_read(pblk, rqd, false);
-	return NVM_IO_DONE;
+}
 
-fail:
-	/* Free allocated pages in new bio */
+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)
+{
+	struct pblk_sec_meta *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;
+	__le64 *lba_list_mem;
+	int nr_secs = rqd->nr_ppas;
+	int i;
+
+	/* Re-use allocated memory for intermediate lbas */
+	lba_list_mem = (((void *)rqd->ppa_list) + pblk_dma_ppa_size);
+
+	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 = kmalloc(sizeof(struct pblk_pr_ctx), GFP_KERNEL);
+	if (!pr_ctx)
+		goto fail_free_pages;
+
+	for (i = 0; i < nr_secs; i++)
+		lba_list_mem[i] = meta_list[i].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;
+	rqd->flags = pblk_set_read_mode(pblk, PBLK_READ_RANDOM);
+
+	pr_ctx->ppa_ptr = NULL;
+	pr_ctx->orig_bio = bio;
+	pr_ctx->bitmap = *read_bitmap;
+	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_add_pages:
+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;
 }
@@ -480,8 +530,15 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
 	/* 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.
 	 */
-	return pblk_partial_read(pblk, rqd, bio, bio_init_idx, read_bitmap);
+	ret = pblk_partial_read_bio(pblk, rqd, bio_init_idx, read_bitmap,
+				    nr_secs);
+	if (ret)
+		goto fail_meta_free;
+
+	return NVM_IO_OK;
 
+fail_meta_free:
+	nvm_dev_dma_free(dev->parent, rqd->meta_list, rqd->dma_meta_list);
 fail_rqd_free:
 	pblk_free_rqd(pblk, rqd, PBLK_READ);
 	return ret;
diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
index 5c6904e..6ebd2e5 100644
--- a/drivers/lightnvm/pblk.h
+++ b/drivers/lightnvm/pblk.h
@@ -119,6 +119,16 @@ struct pblk_g_ctx {
 	u64 lba;
 };
 
+/* partial read context */
+struct pblk_pr_ctx {
+	struct bio *orig_bio;
+	unsigned long bitmap;
+	unsigned int orig_nr_secs;
+	unsigned int bio_init_idx;
+	void *ppa_ptr;
+	dma_addr_t dma_ppa_list;
+};
+
 /* Pad context */
 struct pblk_pad_rq {
 	struct pblk *pblk;
-- 
2.7.4