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    Subject[PATCH AUTOSEL 4.19 016/146] lightnvm: pblk: fix race condition on metadata I/O
    Date
    From: Javier González <javier@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 <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>
    ---
    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 ee774a86cf1e..879227d584e7 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
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