Re: [PATCH 2/6] lightnvm: pblk: protect line bitmap while submitting meta io

[Matias Bjørling]

On 09/22/2017 10:49 AM, Javier González wrote:

On 21 Sep 2017, at 13.26, Rakesh Pandit <rak...@tuxera.com> wrote:

It seems pblk_dealloc_page would race against pblk_alloc_pages for
line bitmap for sector allocation.  The chances are very low but might
as well protect the bitmap properly.  It's not even in fast path.

Signed-off-by: Rakesh Pandit <rak...@tuxera.com>
---
drivers/lightnvm/pblk-core.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index a230125..b92eabc 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -502,12 +502,14 @@ void pblk_dealloc_page(struct pblk *pblk, struct 
pblk_line *line, int nr_secs)
        u64 addr;
        int i;

+       spin_lock(&line->lock);
        addr = find_next_zero_bit(line->map_bitmap,
                                        pblk->lm.sec_per_line, line->cur_sec);
        line->cur_sec = addr - nr_secs;

        for (i = 0; i < nr_secs; i++, line->cur_sec--)
                WARN_ON(!test_and_clear_bit(line->cur_sec, line->map_bitmap));
+       spin_lock(&line->lock);
}

u64 __pblk_alloc_page(struct pblk *pblk, struct pblk_line *line, int nr_secs)
--
2.5.0

Looks good. The reason not to have locks here was that the caller is
always on the write thread - who did the allocation -, since it is error
handling. So there is no protection needed. In any case, it is better to
have it since it is implemented as a helper function.


Reviewed-by: Javier González <jav...@cnexlabs.com>

Thanks, I picked it up.