Re: [PATCH v3 02/10] lightnvm: pblk: simplify partial read path

[Igor Konopko <igor.j.konopko@xxxxxxxxx>]

On 30.03.2019 06:02, Heiner Litz wrote:
> Hi Igor,
> thanks for sending the patch. There are a couple things I don't like too much:
> - the fact that we have to carry around state in form of
> pblk_read_info which somewhat replaces the read_bitmap
> - the fact that sectors are looked up multiple times and hence krefs
> are incremented and decremented unnecessarily
> - the fact that we still bio_advance all over the place
>
> I think we can avoid all above with a new lookup_l2p function which
> does the following (pseudo code):

Thanks for your feedback.
Generally your ideas sounds right and I would try to incorporate it into 
v4 of that patch. I did some basic implementation, but I need to do some 
testing with it. It is slightly different from what you proposed in 
pseudo-code, but I think that my version would also fix the three issues 
which you mention above.

Igor

> bool did_read_from_device = false;
> bool did_read_from_cache = false;
> lookup_l2p_segment() {
>    for (i = 0; i < nr_secs; i++) {
>      ppa = trans_map_get();
>      if (!did_read_from_device && ppa_is_cached(ppa)) {
>        read_from_cache(ppa);
>        did_read_from_cache = true;
>      }
>      if (!did_read_from_cache && !ppa_is_cached(ppa)) {
>        ppa_list[p++] = ppa;
>        kref_get(line);
>        did_read_from_device = true;
>      }
>      else
>        return i;
>    }
>    return i;
> }
>
> This function achieves the following.
> 1) It returns the length (i) of a segment of consecutive cached or
> device sectors. We can use i to split the bio
> 2) Whenever the function above returns we know that the split bio
> either only contains device or cached sectors. This means we can
> finish the split bio without needing read_info
> 3) The function returns after a split, so sectors are never looked up
> twice (no multi-kref inc/dec)
> 4) don't need to bio_advance all over the place, as in a cached bio we
> know that all sectors are cached and we can complete it at once
> 5) because we read from cache within lookup_l2p, we don't have to
> retry externally if secs don't exist in the cache anymore
>
> Note: If we don't want to read_from_cache while holding the trans_lock
> we can release and re-acquire within lookup_l2p.
>
>
> On Fri, Mar 29, 2019 at 2:12 AM Hans Holmberg <hans@xxxxxxxxxxxxx> wrote:
> > On Wed, Mar 27, 2019 at 1:41 PM Igor Konopko <igor.j.konopko@xxxxxxxxx> wrote:
> > > This patch changes the approach to handling partial read path, what is
> > > needed for supporting multi-page bvec, which is currently broken.
> > >
> > > 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 <igor.j.konopko@xxxxxxxxx>
> >
> > I've played around with fio to figure out if there is a read latency
> > performance hit, and I have not found any diff that can't be written
> > off as noise.
> > (i did seq write + random 4k reads with different sizes and checked
> > the latency stats)
> >
> > > ---
> > >   drivers/lightnvm/pblk-core.c |  16 +++
> > >   drivers/lightnvm/pblk-read.c | 276 +++++++++++--------------------------------
> > >   drivers/lightnvm/pblk.h      |  22 ++--
> > >   3 files changed, 97 insertions(+), 217 deletions(-)
> >
> > Nice cleanup :)
> > I hope to find time early next week to go through the patch in depth.
> >
> > Thanks,
> > Hans
> >
> > > diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> > > index 39280c1..f2edec6 100644
> > > --- a/drivers/lightnvm/pblk-core.c
> > > +++ b/drivers/lightnvm/pblk-core.c
> > > @@ -1529,6 +1529,22 @@ void pblk_rq_to_line_put(struct pblk *pblk, struct nvm_rq *rqd)
> > >                  pblk_ppa_to_line_put(pblk, ppa_list[i]);
> > >   }
> > >
> > > +void pblk_rq_to_line_partial_put(struct pblk *pblk, struct nvm_rq *rqd,
> > > +                                       int offset)
> > > +{
> > > +       struct ppa_addr ppa;
> > > +       struct pblk_line *line;
> > > +       int i = offset;
> > > +
> > > +       for (; i < rqd->nr_ppas; i++) {
> > > +               ppa = rqd->ppa_list[i];
> > > +               if (!pblk_ppa_empty(ppa) && !pblk_addr_in_cache(ppa)) {
> > > +                       line = pblk_ppa_to_line(pblk, ppa);
> > > +                       kref_put(&line->ref, pblk_line_put);
> > > +               }
> > > +       }
> > > +}
> > > +
> > >   static void pblk_stop_writes(struct pblk *pblk, struct pblk_line *line)
> > >   {
> > >          lockdep_assert_held(&pblk->l_mg.free_lock);
> > > diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
> > > index 597fe6d..264d1d7 100644
> > > --- a/drivers/lightnvm/pblk-read.c
> > > +++ b/drivers/lightnvm/pblk-read.c
> > > @@ -41,28 +41,30 @@ 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,
> > >                                   struct bio *bio, sector_t blba,
> > > -                                unsigned long *read_bitmap)
> > > +                                struct pblk_read_info *info)
> > >   {
> > >          void *meta_list = rqd->meta_list;
> > > -       struct ppa_addr ppas[NVM_MAX_VLBA];
> > >          int nr_secs = rqd->nr_ppas;
> > >          bool advanced_bio = false;
> > > -       int i, j = 0;
> > > +       int i;
> > >
> > > -       pblk_lookup_l2p_seq(pblk, ppas, blba, nr_secs);
> > > +       pblk_lookup_l2p_seq(pblk, rqd->ppa_list, blba, nr_secs);
> > > +       info->first_sec_from_cache = nr_secs;
> > > +       info->first_sec_from_drive = nr_secs;
> > >
> > >          for (i = 0; i < nr_secs; i++) {
> > > -               struct ppa_addr p = ppas[i];
> > >                  struct pblk_sec_meta *meta = pblk_get_meta(pblk, meta_list, i);
> > >                  sector_t lba = blba + i;
> > >
> > >   retry:
> > > -               if (pblk_ppa_empty(p)) {
> > > +               if (pblk_ppa_empty(rqd->ppa_list[i])) {
> > >                          __le64 addr_empty = cpu_to_le64(ADDR_EMPTY);
> > >
> > > -                       WARN_ON(test_and_set_bit(i, read_bitmap));
> > > -                       meta->lba = addr_empty;
> > > +                       info->secs_from_cache = true;
> > > +                       info->first_sec_from_cache = min_t(int, i,
> > > +                                               info->first_sec_from_cache);
> > >
> > > +                       meta->lba = addr_empty;
> > >                          if (unlikely(!advanced_bio)) {
> > >                                  bio_advance(bio, (i) * PBLK_EXPOSED_PAGE_SIZE);
> > >                                  advanced_bio = true;
> > > @@ -74,13 +76,18 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
> > >                  /* Try to read from write buffer. The address is later checked
> > >                   * on the write buffer to prevent retrieving overwritten data.
> > >                   */
> > > -               if (pblk_addr_in_cache(p)) {
> > > -                       if (!pblk_read_from_cache(pblk, bio, lba, p, i,
> > > -                                                               advanced_bio)) {
> > > -                               pblk_lookup_l2p_seq(pblk, &p, lba, 1);
> > > +               if (pblk_addr_in_cache(rqd->ppa_list[i])) {
> > > +                       if (!pblk_read_from_cache(pblk, bio, lba,
> > > +                                       rqd->ppa_list[i], i, advanced_bio)) {
> > > +                               pblk_lookup_l2p_seq(pblk, &rqd->ppa_list[i],
> > > +                                                       lba, 1);
> > >                                  goto retry;
> > >                          }
> > > -                       WARN_ON(test_and_set_bit(i, read_bitmap));
> > > +
> > > +                       info->secs_from_cache = true;
> > > +                       info->first_sec_from_cache = min_t(int, i,
> > > +                                               info->first_sec_from_cache);
> > > +
> > >                          meta->lba = cpu_to_le64(lba);
> > >                          advanced_bio = true;
> > >   #ifdef CONFIG_NVM_PBLK_DEBUG
> > > @@ -88,7 +95,9 @@ static void pblk_read_ppalist_rq(struct pblk *pblk, struct nvm_rq *rqd,
> > >   #endif
> > >                  } else {
> > >                          /* Read from media non-cached sectors */
> > > -                       rqd->ppa_list[j++] = p;
> > > +                       info->secs_from_drive = true;
> > > +                       info->first_sec_from_drive = min_t(int, i,
> > > +                                               info->first_sec_from_drive);
> > >                  }
> > >
> > >   next:
> > > @@ -223,172 +232,8 @@ 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);
> > > -       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)
> > > +                        sector_t lba, struct pblk_read_info *info)
> > >   {
> > >          struct pblk_sec_meta *meta = pblk_get_meta(pblk, rqd->meta_list, 0);
> > >          struct ppa_addr ppa;
> > > @@ -403,8 +248,8 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
> > >          if (pblk_ppa_empty(ppa)) {
> > >                  __le64 addr_empty = cpu_to_le64(ADDR_EMPTY);
> > >
> > > -               WARN_ON(test_and_set_bit(0, read_bitmap));
> > >                  meta->lba = addr_empty;
> > > +               info->secs_from_cache = true;
> > >                  return;
> > >          }
> > >
> > > @@ -417,14 +262,14 @@ static void pblk_read_rq(struct pblk *pblk, struct nvm_rq *rqd, struct bio *bio,
> > >                          goto retry;
> > >                  }
> > >
> > > -               WARN_ON(test_and_set_bit(0, read_bitmap));
> > >                  meta->lba = cpu_to_le64(lba);
> > > -
> > > +               info->secs_from_cache = true;
> > >   #ifdef CONFIG_NVM_PBLK_DEBUG
> > >                  atomic_long_inc(&pblk->cache_reads);
> > >   #endif
> > >          } else {
> > >                  rqd->ppa_addr = ppa;
> > > +               info->secs_from_drive = true;
> > >          }
> > >   }
> > >
> > > @@ -436,15 +281,12 @@ void pblk_submit_read(struct pblk *pblk, struct bio *bio)
> > >          unsigned int nr_secs = pblk_get_secs(bio);
> > >          struct pblk_g_ctx *r_ctx;
> > >          struct nvm_rq *rqd;
> > > -       struct bio *int_bio;
> > > -       unsigned int bio_init_idx;
> > > -       DECLARE_BITMAP(read_bitmap, NVM_MAX_VLBA);
> > > +       struct bio *int_bio, *split_bio;
> > > +       struct pblk_read_info info = {0};
> > >
> > >          generic_start_io_acct(q, REQ_OP_READ, bio_sectors(bio),
> > >                                &pblk->disk->part0);
> > >
> > > -       bitmap_zero(read_bitmap, nr_secs);
> > > -
> > >          rqd = pblk_alloc_rqd(pblk, PBLK_READ);
> > >
> > >          rqd->opcode = NVM_OP_PREAD;
> > > @@ -456,11 +298,6 @@ void pblk_submit_read(struct pblk *pblk, struct bio *bio)
> > >          r_ctx->start_time = jiffies;
> > >          r_ctx->lba = blba;
> > >
> > > -       /* Save the index for this bio's start. This is needed in case
> > > -        * we need to fill a partial read.
> > > -        */
> > > -       bio_init_idx = pblk_get_bi_idx(bio);
> > > -
> > >          if (pblk_alloc_rqd_meta(pblk, rqd)) {
> > >                  bio_io_error(bio);
> > >                  pblk_free_rqd(pblk, rqd, PBLK_READ);
> > > @@ -474,34 +311,63 @@ void pblk_submit_read(struct pblk *pblk, struct bio *bio)
> > >          int_bio = bio_clone_fast(bio, GFP_KERNEL, &pblk_bio_set);
> > >
> > >          if (nr_secs > 1)
> > > -               pblk_read_ppalist_rq(pblk, rqd, bio, blba, read_bitmap);
> > > +               pblk_read_ppalist_rq(pblk, rqd, int_bio, blba, &info);
> > >          else
> > > -               pblk_read_rq(pblk, rqd, bio, blba, read_bitmap);
> > > +               pblk_read_rq(pblk, rqd, int_bio, blba, &info);
> > >
> > > +split_retry:
> > >          r_ctx->private = bio; /* original bio */
> > >          rqd->bio = int_bio; /* internal bio */
> > >
> > > -       if (bitmap_full(read_bitmap, nr_secs)) {
> > > +       if (info.secs_from_cache && !info.secs_from_drive) {
> > >                  pblk_end_user_read(bio, 0);
> > >                  atomic_inc(&pblk->inflight_io);
> > >                  __pblk_end_io_read(pblk, rqd, false);
> > >                  return;
> > >          }
> > >
> > > -       if (!bitmap_empty(read_bitmap, rqd->nr_ppas)) {
> > > +       if (info.secs_from_cache && info.secs_from_drive) {
> > >                  /* 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.
> > > +                * the drive. In order to handle this, we will use block layer
> > > +                * mechanism to split this request in to smaller ones and make
> > > +                * a chain of it.
> > > +                */
> > > +               int split = max_t(int, info.first_sec_from_cache,
> > > +                                       info.first_sec_from_drive);
> > > +
> > > +               split_bio = bio_split(bio, split * NR_PHY_IN_LOG, GFP_KERNEL,
> > > +                                       &pblk_bio_set);
> > > +               bio_chain(split_bio, bio);
> > > +               generic_make_request(bio);
> > > +
> > > +               /* New bio contains first N sectors of the previous one, so
> > > +                * we can continue to use existing rqd, but we need to shrink
> > > +                * the number of PPAs in it. We also need to release line
> > > +                * references on the rest of the PPAs. Finally we also need
> > > +                * to update pblk_read_info struct properly in order to avoid
> > > +                * another interation of l2p lookup.
> > > +                */
> > > +               bio = split_bio;
> > > +               pblk_rq_to_line_partial_put(pblk, rqd, split);
> > > +#ifdef CONFIG_NVM_PBLK_DEBUG
> > > +               atomic_long_sub((rqd->nr_ppas - split), &pblk->inflight_reads);
> > > +#endif
> > > +               rqd->nr_ppas = split;
> > > +               if (rqd->nr_ppas == 1)
> > > +                       rqd->ppa_addr = rqd->ppa_list[0];
> > > +
> > > +               if (info.first_sec_from_cache > info.first_sec_from_drive)
> > > +                       info.secs_from_cache = false;
> > > +               else
> > > +                       info.secs_from_drive = false;
> > > +
> > > +               /* Recreate int_bio - existing might have some needed internal
> > > +                * fields modified already.
> > >                   */
> > >                  bio_put(int_bio);
> > > -               rqd->bio = NULL;
> > > -               if (pblk_partial_read_bio(pblk, rqd, bio_init_idx, read_bitmap,
> > > -                                           nr_secs)) {
> > > -                       pblk_err(pblk, "read IO submission failed\n");
> > > -                       bio_io_error(bio);
> > > -                       __pblk_end_io_read(pblk, rqd, false);
> > > -               }
> > > -               return;
> > > +               int_bio = bio_clone_fast(bio, GFP_KERNEL, &pblk_bio_set);
> > > +               goto split_retry;
> > >          }
> > >
> > >          /* All sectors are to be read from the device */
> > > diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> > > index a3c925d..e284a93 100644
> > > --- a/drivers/lightnvm/pblk.h
> > > +++ b/drivers/lightnvm/pblk.h
> > > @@ -123,18 +123,6 @@ struct pblk_g_ctx {
> > >          u64 lba;
> > >   };
> > >
> > > -/* partial read context */
> > > -struct pblk_pr_ctx {
> > > -       struct bio *orig_bio;
> > > -       DECLARE_BITMAP(bitmap, NVM_MAX_VLBA);
> > > -       unsigned int orig_nr_secs;
> > > -       unsigned int bio_init_idx;
> > > -       void *ppa_ptr;
> > > -       dma_addr_t dma_ppa_list;
> > > -       u64 lba_list_mem[NVM_MAX_VLBA];
> > > -       u64 lba_list_media[NVM_MAX_VLBA];
> > > -};
> > > -
> > >   /* Pad context */
> > >   struct pblk_pad_rq {
> > >          struct pblk *pblk;
> > > @@ -726,6 +714,14 @@ struct pblk_line_ws {
> > >          struct work_struct ws;
> > >   };
> > >
> > > +/* L2P lookup on read path info */
> > > +struct pblk_read_info {
> > > +       int first_sec_from_cache;
> > > +       int first_sec_from_drive;
> > > +       bool secs_from_cache;
> > > +       bool secs_from_drive;
> > > +};
> > > +
> > >   #define pblk_g_rq_size (sizeof(struct nvm_rq) + sizeof(struct pblk_g_ctx))
> > >   #define pblk_w_rq_size (sizeof(struct nvm_rq) + sizeof(struct pblk_c_ctx))
> > >
> > > @@ -809,6 +805,8 @@ struct pblk_line *pblk_line_get_first_data(struct pblk *pblk);
> > >   struct pblk_line *pblk_line_replace_data(struct pblk *pblk);
> > >   void pblk_ppa_to_line_put(struct pblk *pblk, struct ppa_addr ppa);
> > >   void pblk_rq_to_line_put(struct pblk *pblk, struct nvm_rq *rqd);
> > > +void pblk_rq_to_line_partial_put(struct pblk *pblk, struct nvm_rq *rqd,
> > > +                                       int offset);
> > >   int pblk_line_recov_alloc(struct pblk *pblk, struct pblk_line *line);
> > >   void pblk_line_recov_close(struct pblk *pblk, struct pblk_line *line);
> > >   struct pblk_line *pblk_line_get_data(struct pblk *pblk);
> > > --
> > > 2.9.5