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Date: Fri, 1 Jun 2018 12:48:10 +0200
From: Javier González <javigon.napster@...il.com>
To: Matias Bjørling <mb@...htnvm.io>
Cc: Javier González <javier@...igon.com>,
Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lightnvm: pblk: remove unnecessary bio_get/put
> On 1 Jun 2018, at 12.42, Matias Bjørling <mb@...htnvm.io> wrote:
>
>> On 06/01/2018 12:22 PM, Javier González wrote:
>> Hi Matias,
>> I see that you did not pick up this patch for 4.18. Any reason for it?
>> Thanks,
>> Javier
>>> On 16 Apr 2018, at 12.22, Javier González <javier@...igon.com> 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 avoid 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 | 57 +++++++++++++++++++-------------------------
>>> 1 file changed, 24 insertions(+), 33 deletions(-)
>>>
>>> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
>>> index 2f8224354c62..5464e4177c87 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;
>>> @@ -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:
>>> pr_err("pblk: failed to perform partial read\n");
>>>
>>> /* Free allocated pages in new bio */
>>> - pblk_bio_free_pages(pblk, bio, 0, new_bio->bi_vcnt);
>>> + pblk_bio_free_pages(pblk, orig_bio, 0, new_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,
>>> +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;
>>>
>>> ret = pblk_submit_io(pblk, rqd);
>>> if (ret) {
>>> pr_err("pblk: read IO submission failed\n");
>>> - 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);
>>> --
>>> 2.7.4
>
> You sent a larger patch serie afterwards that I thought took precedent (and not included in for-4.18/pblk). Feel free to rebase and resend.
Sounds good. I thought you had some comments on it - that’s why I waited a couple of days after you sent the PR. I’ll resend now. Can you apply it to the 4.18 PR?
Thanks!
Javier.
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