lightnvm: pblk: fix erase counters on error fail

When block erases fail, these blocks are marked bad. The number of valid
blocks in the line was not updated, which could cause an infinite loop
on the erase path.

Fix this atomic counter and, in order to avoid taking an irq lock on the
interrupt context, make the erase counters atomic too.

Also, in the case that a significant number of blocks become bad in a
line, the result is the double shared metadata buffer (emeta) to stop
the pipeline until all metadata is flushed to the media. Increase the
number of metadata lines from 2 to 4 to avoid this case.

Fixes: a4bd217b43 "lightnvm: physical block device (pblk) target"

Signed-off-by: Javier González <javier@cnexlabs.com>
Reviewed-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/pblk-rl.c

@@ -107,9 +107,10 @@ void pblk_rl_set_gc_rsc(struct pblk_rl *rl, int rsv)
 void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
 {
 	struct pblk *pblk = container_of(rl, struct pblk, rl);
+	int blk_in_line = atomic_read(&line->blk_in_line);
 	int ret;
 
-	atomic_add(line->blk_in_line, &rl->free_blocks);
+	atomic_add(blk_in_line, &rl->free_blocks);
 	/* Rates will not change that often - no need to lock update */
 	ret = pblk_rl_update_rates(rl, rl->rb_budget);
 
@@ -122,9 +123,10 @@ void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
 void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line)
 {
 	struct pblk *pblk = container_of(rl, struct pblk, rl);
+	int blk_in_line = atomic_read(&line->blk_in_line);
 	int ret;
 
-	atomic_sub(line->blk_in_line, &rl->free_blocks);
+	atomic_sub(blk_in_line, &rl->free_blocks);
 
 	/* Rates will not change that often - no need to lock update */
 	ret = pblk_rl_update_rates(rl, rl->rb_budget);