[PATCH AUTOSEL 4.18 014/126] lightnvm: pblk: fix race condition on metadata I/O

[Sasha Levin]

From: Javier González <jav...@javigon.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 <jav...@cnexlabs.com>
Signed-off-by: Matias Bjørling <m...@lightnvm.io>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 drivers/lightnvm/pblk-write.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index f353e52941f5..89ac60d4849e 100644
--- a/drivers/lightnvm/pblk-write.c
+++ b/drivers/lightnvm/pblk-write.c
@@ -417,12 +417,11 @@ int pblk_submit_meta_io(struct pblk *pblk, struct 
pblk_line *meta_line)
                        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_submit_meta_io(struct pblk *pblk,
        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))
-- 
2.17.1