[PATCH 4.19 062/361] lightnvm: pblk: fix race condition on metadata I/O

Greg Kroah-Hartman
2018-11-12T00:15:39Z

From: Javier González <javier@cnexlabs.com>

[ Upstream commit d8adaa3b86324c6186d0adf74bc256bdacfffdb6 ]

In pblk, when a new line is allocated, metadata for the previously
written line is scheduled. This is done through a fixed memory region
that is shared through time and contexts across different lines and
therefore protected by a lock. Unfortunately, this lock is not properly
covering all the metadata used for sharing this memory regions,
resulting in a race condition.

This patch fixes this race condition by protecting this metadata
properly.

Fixes: dd2a43437337 ("lightnvm: pblk: sched. metadata on write thread")
Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/lightnvm/pblk-write.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/lightnvm/pblk-write.c
+++ b/drivers/lightnvm/pblk-write.c
@@ -417,12 +417,11 @@ int pblk_submit_meta_io(struct pblk *pbl
rqd->ppa_list[i] = addr_to_gen_ppa(pblk, paddr, id);
}

+ spin_lock(&l_mg->close_lock);
emeta->mem += rq_len;
- if (emeta->mem >= lm->emeta_len[0]) {
- spin_lock(&l_mg->close_lock);
+ if (emeta->mem >= lm->emeta_len[0])
list_del(&meta_line->list);
- spin_unlock(&l_mg->close_lock);
- }
+ spin_unlock(&l_mg->close_lock);

pblk_down_page(pblk, rqd->ppa_list, rqd->nr_ppas);

@@ -491,14 +490,15 @@ static struct pblk_line *pblk_should_sub
struct pblk_line *meta_line;

spin_lock(&l_mg->close_lock);
-retry:
if (list_empty(&l_mg->emeta_list)) {
spin_unlock(&l_mg->close_lock);
return NULL;
}
meta_line = list_first_entry(&l_mg->emeta_list, struct pblk_line, list);
- if (meta_line->emeta->mem >= lm->emeta_len[0])
- goto retry;
+ if (meta_line->emeta->mem >= lm->emeta_len[0]) {
+ spin_unlock(&l_mg->close_lock);
+ return NULL;
+ }
spin_unlock(&l_mg->close_lock);

if (!pblk_valid_meta_ppa(pblk, meta_line, data_rqd))