[PATCH 16/18] lightnvm: pblk: enable 1 LUN configuration

[Javier González]

Metadata I/Os are scheduled to minimize their impact on user data I/Os.
When there are enough LUNs instantiated (i.e., enought bandwidth), it is
easy to interleave metadata and data one after the other so that
metadata I/Os are the ones being blocked and not viceversa.

We do this by calculating the distance between the I/Os in terms of the
LUNs that are not in used, and selecting a free LUN that satisfies a
the simple heuristic that medatata is scheduled behind. The per-LUN
semaphores guarantee consistency. This works fine on >1 LUN
configuration. However, when a signle LUN is instantiated, this design
leads to a deadlock, where metadata waits to be scheduled on a free LUN.

This patch implements the 1 LUN case by simply scheduling the medatada
I/O after the data I/O. In the process, we refactor the way a line is
replaced to ensure that metadata writes are submitted after data writes
in order to guarantee block sequentiality. Note that, since there is
only one LUN, both I/Os will block each other by design. However, such
configuration only pursues tight read latencies, not write bandwidth.

Signed-off-by: Javier González 
Signed-off-by: Matias Bjørling 
---
 drivers/lightnvm/pblk-core.c  | 17 ++---
 drivers/lightnvm/pblk-init.c  |  8 ++--
 drivers/lightnvm/pblk-map.c   | 21 -
 drivers/lightnvm/pblk-write.c |  8 +---
 drivers/lightnvm/pblk.h   |  2 +-
 5 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index 1f746e31e379..873b66200678 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -1326,17 +1326,17 @@ void pblk_pipeline_stop(struct pblk *pblk)
spin_unlock(_mg->free_lock);
 }
 
-void pblk_line_replace_data(struct pblk *pblk)
+struct pblk_line *pblk_line_replace_data(struct pblk *pblk)
 {
struct pblk_line_mgmt *l_mg = >l_mg;
-   struct pblk_line *cur, *new;
+   struct pblk_line *cur, *new = NULL;
unsigned int left_seblks;
int is_next = 0;
 
cur = l_mg->data_line;
new = l_mg->data_next;
if (!new)
-   return;
+   goto out;
l_mg->data_line = new;
 
spin_lock(_mg->free_lock);
@@ -1344,7 +1344,7 @@ void pblk_line_replace_data(struct pblk *pblk)
l_mg->data_line = NULL;
l_mg->data_next = NULL;
spin_unlock(_mg->free_lock);
-   return;
+   goto out;
}
 
pblk_line_setup_metadata(new, l_mg, >lm);
@@ -1356,7 +1356,7 @@ void pblk_line_replace_data(struct pblk *pblk)
/* If line is not fully erased, erase it */
if (atomic_read(>left_eblks)) {
if (pblk_line_erase(pblk, new))
-   return;
+   goto out;
} else {
io_schedule();
}
@@ -1367,7 +1367,7 @@ void pblk_line_replace_data(struct pblk *pblk)
if (!pblk_line_init_metadata(pblk, new, cur)) {
new = pblk_line_retry(pblk, new);
if (!new)
-   return;
+   goto out;
 
goto retry_setup;
}
@@ -1375,7 +1375,7 @@ void pblk_line_replace_data(struct pblk *pblk)
if (!pblk_line_init_bb(pblk, new, 1)) {
new = pblk_line_retry(pblk, new);
if (!new)
-   return;
+   goto out;
 
goto retry_setup;
}
@@ -1399,6 +1399,9 @@ void pblk_line_replace_data(struct pblk *pblk)
 
if (is_next)
pblk_rl_free_lines_dec(>rl, l_mg->data_next);
+
+out:
+   return new;
 }
 
 void pblk_line_free(struct pblk *pblk, struct pblk_line *line)
diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 12c05aebac16..0409839cc8fc 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -714,8 +714,12 @@ static int pblk_lines_init(struct pblk *pblk)
}
 
lm->emeta_bb = geo->nr_luns - i;
-   lm->min_blk_line = 1 + DIV_ROUND_UP(lm->smeta_sec + lm->emeta_sec[0],
-   geo->sec_per_blk);
+
+   lm->min_blk_line = 1;
+   if (geo->nr_luns > 1)
+   lm->min_blk_line += DIV_ROUND_UP(lm->smeta_sec +
+   lm->emeta_sec[0], geo->sec_per_blk);
+
if (lm->min_blk_line > lm->blk_per_line) {
pr_err("pblk: config. not supported. Min. LUN in line:%d\n",
lm->blk_per_line);
diff --git a/drivers/lightnvm/pblk-map.c b/drivers/lightnvm/pblk-map.c
index fddb924f6dde..3bc4c94f9cf2 100644
--- a/drivers/lightnvm/pblk-map.c
+++ b/drivers/lightnvm/pblk-map.c
@@ -25,13 +25,23 @@ static void pblk_map_page_data(struct pblk *pblk, unsigned 

[PATCH 16/18] lightnvm: pblk: enable 1 LUN configuration

[Javier González]

Metadata I/Os are scheduled to minimize their impact on user data I/Os.
When there are enough LUNs instantiated (i.e., enought bandwidth), it is
easy to interleave metadata and data one after the other so that
metadata I/Os are the ones being blocked and not viceversa.

We do this by calculating the distance between the I/Os in terms of the
LUNs that are not in used, and selecting a free LUN that satisfies a
the simple heuristic that medatata is scheduled behind. The per-LUN
semaphores guarantee consistency. This works fine on >1 LUN
configuration. However, when a signle LUN is instantiated, this design
leads to a deadlock, where metadata waits to be scheduled on a free LUN.

This patch implements the 1 LUN case by simply scheduling the medatada
I/O after the data I/O. In the process, we refactor the way a line is
replaced to ensure that metadata writes are submitted after data writes
in order to guarantee block sequentiality. Note that, since there is
only one LUN, both I/Os will block each other by design. However, such
configuration only pursues tight read latencies, not write bandwidth.

Signed-off-by: Javier González 
Signed-off-by: Matias Bjørling 
---
 drivers/lightnvm/pblk-core.c  | 17 ++---
 drivers/lightnvm/pblk-init.c  |  8 ++--
 drivers/lightnvm/pblk-map.c   | 21 -
 drivers/lightnvm/pblk-write.c |  8 +---
 drivers/lightnvm/pblk.h   |  2 +-
 5 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index 1f746e31e379..873b66200678 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -1326,17 +1326,17 @@ void pblk_pipeline_stop(struct pblk *pblk)
spin_unlock(_mg->free_lock);
 }
 
-void pblk_line_replace_data(struct pblk *pblk)
+struct pblk_line *pblk_line_replace_data(struct pblk *pblk)
 {
struct pblk_line_mgmt *l_mg = >l_mg;
-   struct pblk_line *cur, *new;
+   struct pblk_line *cur, *new = NULL;
unsigned int left_seblks;
int is_next = 0;
 
cur = l_mg->data_line;
new = l_mg->data_next;
if (!new)
-   return;
+   goto out;
l_mg->data_line = new;
 
spin_lock(_mg->free_lock);
@@ -1344,7 +1344,7 @@ void pblk_line_replace_data(struct pblk *pblk)
l_mg->data_line = NULL;
l_mg->data_next = NULL;
spin_unlock(_mg->free_lock);
-   return;
+   goto out;
}
 
pblk_line_setup_metadata(new, l_mg, >lm);
@@ -1356,7 +1356,7 @@ void pblk_line_replace_data(struct pblk *pblk)
/* If line is not fully erased, erase it */
if (atomic_read(>left_eblks)) {
if (pblk_line_erase(pblk, new))
-   return;
+   goto out;
} else {
io_schedule();
}
@@ -1367,7 +1367,7 @@ void pblk_line_replace_data(struct pblk *pblk)
if (!pblk_line_init_metadata(pblk, new, cur)) {
new = pblk_line_retry(pblk, new);
if (!new)
-   return;
+   goto out;
 
goto retry_setup;
}
@@ -1375,7 +1375,7 @@ void pblk_line_replace_data(struct pblk *pblk)
if (!pblk_line_init_bb(pblk, new, 1)) {
new = pblk_line_retry(pblk, new);
if (!new)
-   return;
+   goto out;
 
goto retry_setup;
}
@@ -1399,6 +1399,9 @@ void pblk_line_replace_data(struct pblk *pblk)
 
if (is_next)
pblk_rl_free_lines_dec(>rl, l_mg->data_next);
+
+out:
+   return new;
 }
 
 void pblk_line_free(struct pblk *pblk, struct pblk_line *line)
diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 12c05aebac16..0409839cc8fc 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -714,8 +714,12 @@ static int pblk_lines_init(struct pblk *pblk)
}
 
lm->emeta_bb = geo->nr_luns - i;
-   lm->min_blk_line = 1 + DIV_ROUND_UP(lm->smeta_sec + lm->emeta_sec[0],
-   geo->sec_per_blk);
+
+   lm->min_blk_line = 1;
+   if (geo->nr_luns > 1)
+   lm->min_blk_line += DIV_ROUND_UP(lm->smeta_sec +
+   lm->emeta_sec[0], geo->sec_per_blk);
+
if (lm->min_blk_line > lm->blk_per_line) {
pr_err("pblk: config. not supported. Min. LUN in line:%d\n",
lm->blk_per_line);
diff --git a/drivers/lightnvm/pblk-map.c b/drivers/lightnvm/pblk-map.c
index fddb924f6dde..3bc4c94f9cf2 100644
--- a/drivers/lightnvm/pblk-map.c
+++ b/drivers/lightnvm/pblk-map.c
@@ -25,13 +25,23 @@ static void pblk_map_page_data(struct pblk *pblk, unsigned 
int sentry,