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Date: Fri, 1 Jun 2018 14:05:14 +0200
From: Matias Bjørling <mb@...htnvm.io>
To: Javier González <javier@...igon.com>,
Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
Javier González <javier@...xlabs.com>
Subject: Re: [PATCH] lightnvm: pblk: remove unnecessary bio_get/put
On 06/01/2018 02:01 PM, Javier González wrote:
> In the read path, pblk gets a reference to the incoming bio and puts it
> after ending the bio. Though this behavior is correct, it is unnecessary
> since pblk is the one putting the bio, therefore, it cannot disappear
> underneath it.
>
> Removing this reference, allows to clean up rqd->bio and avoids pointer
> bouncing for the different read paths. Now, the incoming bio always
> resides in the read context and pblk's internal bios (if any) reside in
> rqd->bio.
>
> Signed-off-by: Javier González <javier@...xlabs.com>
> ---
> drivers/lightnvm/pblk-read.c | 65 +++++++++++++++++++-------------------------
> 1 file changed, 28 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
> index fa7b60f852d9..38360de23d4e 100644
> --- a/drivers/lightnvm/pblk-read.c
> +++ b/drivers/lightnvm/pblk-read.c
> @@ -39,10 +39,10 @@ static int pblk_read_from_cache(struct pblk *pblk, struct bio *bio,
> }
>
> static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
> - sector_t blba, unsigned long *read_bitmap)
> + struct bio *bio, sector_t blba,
> + unsigned long *read_bitmap)
> {
> struct pblk_sec_meta *meta_list = rqd->meta_list;
> - struct bio *bio = rqd->bio;
> struct ppa_addr ppas[PBLK_MAX_REQ_ADDRS];
> int nr_secs = rqd->nr_ppas;
> bool advanced_bio = false;
> @@ -189,7 +189,6 @@ static void pblk_end_user_read(struct bio *bio)
> WARN_ONCE(bio->bi_status, "pblk: corrupted read bio\n");
> #endif
> bio_endio(bio);
> - bio_put(bio);
> }
>
> static void __pblk_end_io_read(struct pblk *pblk, struct nvm_rq *rqd,
> @@ -197,23 +196,18 @@ static void __pblk_end_io_read(struct pblk *pblk, struct nvm_rq *rqd,
> {
> struct nvm_tgt_dev *dev = pblk->dev;
> struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
> - struct bio *bio = rqd->bio;
> + struct bio *int_bio = rqd->bio;
> unsigned long start_time = r_ctx->start_time;
>
> generic_end_io_acct(dev->q, READ, &pblk->disk->part0, start_time);
>
> if (rqd->error)
> pblk_log_read_err(pblk, rqd);
> -#ifdef CONFIG_NVM_DEBUG
> - else
> - WARN_ONCE(bio->bi_status, "pblk: corrupted read error\n");
> -#endif
>
> pblk_read_check_seq(pblk, rqd, r_ctx->lba);
>
> - bio_put(bio);
> - if (r_ctx->private)
> - pblk_end_user_read((struct bio *)r_ctx->private);
> + if (int_bio)
> + bio_put(int_bio);
>
> if (put_line)
> pblk_read_put_rqd_kref(pblk, rqd);
> @@ -230,16 +224,19 @@ static void __pblk_end_io_read(struct pblk *pblk, struct nvm_rq *rqd,
> static void pblk_end_io_read(struct nvm_rq *rqd)
> {
> struct pblk *pblk = rqd->private;
> + struct pblk_g_ctx *r_ctx = nvm_rq_to_pdu(rqd);
> + struct bio *bio = (struct bio *)r_ctx->private;
>
> + pblk_end_user_read(bio);
> __pblk_end_io_read(pblk, rqd, true);
> }
>
> -static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
> - unsigned int bio_init_idx,
> - unsigned long *read_bitmap)
> +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)
> {
> - struct bio *new_bio, *bio = rqd->bio;
> struct pblk_sec_meta *meta_list = rqd->meta_list;
> + struct bio *new_bio;
> struct bio_vec src_bv, dst_bv;
> void *ppa_ptr = NULL;
> void *src_p, *dst_p;
> @@ -256,11 +253,11 @@ static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
> new_bio = bio_alloc(GFP_KERNEL, nr_holes);
>
> if (pblk_bio_add_pages(pblk, new_bio, GFP_KERNEL, nr_holes))
> - goto err_add_pages;
> + goto fail_add_pages;
>
> if (nr_holes != new_bio->bi_vcnt) {
> pr_err("pblk: malformed bio\n");
> - goto err;
> + goto fail;
> }
>
> for (i = 0; i < nr_secs; i++)
> @@ -283,7 +280,7 @@ static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
> if (ret) {
> bio_put(rqd->bio);
> pr_err("pblk: sync read IO submission failed\n");
> - goto err;
> + goto fail;
> }
>
> if (rqd->error) {
> @@ -319,7 +316,7 @@ static int pblk_partial_read_bio(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 = bio->bi_io_vec[bio_init_idx + hole];
> + dst_bv = orig_bio->bi_io_vec[bio_init_idx + hole];
>
> src_p = kmap_atomic(src_bv.bv_page);
> dst_p = kmap_atomic(dst_bv.bv_page);
> @@ -338,28 +335,26 @@ static int pblk_partial_read_bio(struct pblk *pblk, struct nvm_rq *rqd,
>
> bio_put(new_bio);
>
> - /* Complete the original bio and associated request */
> - bio_endio(bio);
> - rqd->bio = bio;
> + /* restore original request */
> + rqd->bio = NULL;
> rqd->nr_ppas = nr_secs;
>
> __pblk_end_io_read(pblk, rqd, false);
> - return NVM_IO_OK;
> + return NVM_IO_DONE;
>
> -err:
> +fail:
> /* Free allocated pages in new bio */
> pblk_bio_free_pages(pblk, new_bio, 0, new_bio->bi_vcnt);
> -err_add_pages:
> +fail_add_pages:
> pr_err("pblk: failed to perform partial read\n");
> __pblk_end_io_read(pblk, rqd, false);
> return NVM_IO_ERR;
> }
>
> -static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd,
> +static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
> sector_t lba, unsigned long *read_bitmap)
> {
> struct pblk_sec_meta *meta_list = rqd->meta_list;
> - struct bio *bio = rqd->bio;
> struct ppa_addr ppa;
>
> pblk_lookup_l2p_seq(pblk, &ppa, lba, 1);
> @@ -423,14 +418,15 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
> rqd = pblk_alloc_rqd(pblk, PBLK_READ);
>
> rqd->opcode = NVM_OP_PREAD;
> - rqd->bio = bio;
> rqd->nr_ppas = nr_secs;
> + rqd->bio = NULL; /* cloned bio if needed */
> rqd->private = pblk;
> rqd->end_io = pblk_end_io_read;
>
> 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.
> @@ -448,17 +444,15 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
> rqd->ppa_list = rqd->meta_list + pblk_dma_meta_size;
> rqd->dma_ppa_list = rqd->dma_meta_list + pblk_dma_meta_size;
>
> - pblk_read_ppalist_rq(pblk, rqd, blba, &read_bitmap);
> + pblk_read_ppalist_rq(pblk, rqd, bio, blba, &read_bitmap);
> } else {
> - pblk_read_rq(pblk, rqd, blba, &read_bitmap);
> + pblk_read_rq(pblk, rqd, bio, blba, &read_bitmap);
> }
>
> - bio_get(bio);
> if (bitmap_full(&read_bitmap, nr_secs)) {
> - bio_endio(bio);
> atomic_inc(&pblk->inflight_io);
> __pblk_end_io_read(pblk, rqd, false);
> - return NVM_IO_OK;
> + return NVM_IO_DONE;
> }
>
> /* All sectors are to be read from the device */
> @@ -473,13 +467,10 @@ int pblk_submit_read(struct pblk *pblk, struct bio *bio)
> }
>
> rqd->bio = int_bio;
> - r_ctx->private = bio;
>
> if (pblk_submit_io(pblk, rqd)) {
> pr_err("pblk: read IO submission failed\n");
> ret = NVM_IO_ERR;
> - if (int_bio)
> - bio_put(int_bio);
> goto fail_end_io;
> }
>
> @@ -489,7 +480,7 @@ 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_bio(pblk, rqd, bio_init_idx, &read_bitmap);
> + return pblk_partial_read(pblk, rqd, bio, bio_init_idx, &read_bitmap);
>
> fail_rqd_free:
> pblk_free_rqd(pblk, rqd, PBLK_READ);
>
Hi Jens,
Would you please pick this up as well?
Signed-off-by: Matias Bjørling <mb@...htnvm.io>
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