Re: [PATCH 3/3] lightnvm: pblk: take write semaphore on metadata

From: Matias BjÃrling
Date: Wed Aug 29 2018 - 09:08:19 EST

On 08/29/2018 10:56 AM, Javier GonzÃlez 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 GonzÃlez <javier@xxxxxxxxxxxx>
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)
@@ -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);
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,