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SubjectRe: [PATCH 3/3] lightnvm: pblk: take write semaphore on metadata
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On 08/29/2018 10:56 AM, Javier González wrote:
> pblk guarantees write ordering at a chunk level through a per open chunk
> semaphore. At this point, since we only have an open I/O stream for both
> user and GC data, the semaphore is per parallel unit.
>
> For the metadata I/O that is synchronous, the semaphore is not needed as
> ordering is guaranteed. However, if the metadata scheme changes or
> multiple streams are open, this guarantee might not be preserved.
>
> This patch makes sure that all writes go through the semaphore, even for
> synchronous I/O. This is consistent with pblk's write I/O model. It also
> simplifies maintenance since changes in the metadata scheme could cause
> ordering issues.
>
> Signed-off-by: Javier González <javier@cnexlabs.com>
> ---
> drivers/lightnvm/pblk-core.c | 16 +++++++++++++++-
> drivers/lightnvm/pblk.h | 1 +
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> index 767178185f19..1e4dc0c1ed88 100644
> --- a/drivers/lightnvm/pblk-core.c
> +++ b/drivers/lightnvm/pblk-core.c
> @@ -558,6 +558,20 @@ int pblk_submit_io_sync(struct pblk *pblk, struct nvm_rq *rqd)
> return ret;
> }
>
> +int pblk_submit_io_sync_sem(struct pblk *pblk, struct nvm_rq *rqd)
> +{
> + struct ppa_addr *ppa_list;
> + int ret;
> +
> + ppa_list = (rqd->nr_ppas > 1) ? rqd->ppa_list : &rqd->ppa_addr;
> +
> + pblk_down_page(pblk, ppa_list, rqd->nr_ppas);

If the debug stuff is killed inside __pblk_down_page, then ppa_list and
rqd->nr_ppas does not need to be passed, and this function can be
inlined in its caller. Can we kill it? I'll make the patch if you like.

> + ret = pblk_submit_io_sync(pblk, rqd);
> + pblk_up_page(pblk, ppa_list, rqd->nr_ppas);
> +
> + return ret;
> +}
> +
> static void pblk_bio_map_addr_endio(struct bio *bio)
> {
> bio_put(bio);
> @@ -788,7 +802,7 @@ static int pblk_line_smeta_write(struct pblk *pblk, struct pblk_line *line,
> meta_list[i].lba = lba_list[paddr] = addr_empty;
> }
>
> - ret = pblk_submit_io_sync(pblk, &rqd);
> + ret = pblk_submit_io_sync_sem(pblk, &rqd);
> if (ret) {
> pblk_err(pblk, "smeta I/O submission failed: %d\n", ret);
> bio_put(bio);
> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> index c0d9eddd344b..54f937c1fb62 100644
> --- a/drivers/lightnvm/pblk.h
> +++ b/drivers/lightnvm/pblk.h
> @@ -793,6 +793,7 @@ void pblk_log_write_err(struct pblk *pblk, struct nvm_rq *rqd);
> void pblk_log_read_err(struct pblk *pblk, struct nvm_rq *rqd);
> int pblk_submit_io(struct pblk *pblk, struct nvm_rq *rqd);
> int pblk_submit_io_sync(struct pblk *pblk, struct nvm_rq *rqd);
> +int pblk_submit_io_sync_sem(struct pblk *pblk, struct nvm_rq *rqd);
> int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line);
> void pblk_check_chunk_state_update(struct pblk *pblk, struct nvm_rq *rqd);
> struct bio *pblk_bio_map_addr(struct pblk *pblk, void *data,
>

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