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

From: "Javier González" <javier@javigon.com>
To: mb@lightnvm.io
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Javier González" <javier@cnexlabs.com>
Subject: [PATCH 3/3] lightnvm: pblk: take write semaphore on metadata
Date: Tue, 11 Sep 2018 13:24:51 +0200	[thread overview]
Message-ID: <1536665091-12641-4-git-send-email-javier@cnexlabs.com> (raw)
In-Reply-To: <1536665091-12641-1-git-send-email-javier@cnexlabs.com>

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 49cef93e328e..a3ce4a36dd33 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -557,6 +557,20 @@ 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_chunk(pblk, ppa_list[0]);
+	ret = pblk_submit_io_sync(pblk, rqd);
+	pblk_up_chunk(pblk, ppa_list[0]);
+
+	return ret;
+}
+
 static void pblk_bio_map_addr_endio(struct bio *bio)
 {
 	bio_put(bio);
@@ -787,7 +801,7 @@ 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 02e2c02b0cf4..4c015c457197 100644
--- a/drivers/lightnvm/pblk.h
+++ b/drivers/lightnvm/pblk.h
@@ -792,6 +792,7 @@ 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,
-- 
2.7.4

