lightnvm: pblk: set conservative threshold for user writes

In a worst-case scenario (random writes), OP% of sectors
in each line will be invalid, and we will then need
to move data out of 100/OP% lines to free a single line.

So, to prevent the possibility of running out of lines,
temporarily block user writes when there is less than
100/OP% free lines.

Also ensure that pblk creation does not produce instances
with insufficient over provisioning.

Insufficient over-provising is not a problem on real hardware,
but often an issue when running QEMU simulations (with few lines).
100 lines is enough to create a sane instance with the standard
(11%) over provisioning.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
index db55a1c89997..76116d5f78e4 100644
--- a/drivers/lightnvm/pblk-rl.c
+++ b/drivers/lightnvm/pblk-rl.c
@@ -214,11 +214,10 @@ void pblk_rl_init(struct pblk_rl *rl, int budget)
 	struct nvm_geo *geo = &dev->geo;
 	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 	struct pblk_line_meta *lm = &pblk->lm;
-	int min_blocks = lm->blk_per_line * PBLK_GC_RSV_LINE;
 	int sec_meta, blk_meta;
-
 	unsigned int rb_windows;
 
+
 	/* Consider sectors used for metadata */
 	sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;
 	blk_meta = DIV_ROUND_UP(sec_meta, geo->clba);
@@ -226,7 +225,7 @@ void pblk_rl_init(struct pblk_rl *rl, int budget)
 	rl->high = pblk->op_blks - blk_meta - lm->blk_per_line;
 	rl->high_pw = get_count_order(rl->high);
 
-	rl->rsv_blocks = min_blocks;
+	rl->rsv_blocks = pblk_get_min_chks(pblk);
 
 	/* This will always be a power-of-2 */
 	rb_windows = budget / NVM_MAX_VLBA;