lightnvm: pblk: fix race condition on metadata I/O

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>

diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index 508c63701eda63bbfc6458616e2084391bb52368..df99c45778d4a5a8190f096bde043fd90563236e 100644 (file)
--- 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))