> On 6 Sep 2018, at 00.51, Hans Holmberg <hans.ml.holmberg@xxxxxxxxxxxxx> wrote:
>
> On Wed, Sep 5, 2018 at 10:40 AM Jia-Ju Bai <baijiaju1990@xxxxxxxxx> wrote:
>> The driver may sleep with holding a spinlock.
>>
>> The function call paths (from bottom to top) in Linux-4.16 are:
>>
>> [FUNC] nvm_dev_dma_alloc(GFP_KERNEL)
>> drivers/lightnvm/pblk-core.c, 754:
>> nvm_dev_dma_alloc in pblk_line_submit_smeta_io
>> drivers/lightnvm/pblk-core.c, 1048:
>> pblk_line_submit_smeta_io in pblk_line_init_bb
>> drivers/lightnvm/pblk-core.c, 1434:
>> pblk_line_init_bb in pblk_line_replace_data
>> drivers/lightnvm/pblk-recovery.c, 980:
>> pblk_line_replace_data in pblk_recov_l2p
>> drivers/lightnvm/pblk-recovery.c, 976:
>> spin_lock in pblk_recov_l2p
>>
>> [FUNC] bio_map_kern(GFP_KERNEL)
>> drivers/lightnvm/pblk-core.c, 762:
>> bio_map_kern in pblk_line_submit_smeta_io
>> drivers/lightnvm/pblk-core.c, 1048:
>> pblk_line_submit_smeta_io in pblk_line_init_bb
>> drivers/lightnvm/pblk-core.c, 1434:
>> pblk_line_init_bb in pblk_line_replace_data
>> drivers/lightnvm/pblk-recovery.c, 980:
>> pblk_line_replace_data in pblk_recov_l2p
>> drivers/lightnvm/pblk-recovery.c, 976:
>> spin_lock in pblk_recov_l2p
>>
>> To fix these bugs, the call to pblk_line_replace_data()
>> is moved out of the spinlock protection.
>>
>> These bugs are found by my static analysis tool DSAC.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
>> ---
>> v2:
>> * Move the call to pblk_line_replace_data() out of the spinlock
>> protection, instead of v1 that changes GFP_KERNEL to GFP_ATOMIC in
>> the calls to bio_map_kern() and nvm_dev_dma_alloc().
>> Thanks Javier for good advice.
>> ---
>> drivers/lightnvm/pblk-recovery.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
>> index 3a5069183859..5fde414d78bb 100644
>> --- a/drivers/lightnvm/pblk-recovery.c
>> +++ b/drivers/lightnvm/pblk-recovery.c
>> @@ -955,12 +955,14 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
>> }
>> }
>>
>> - spin_lock(&l_mg->free_lock);
>> if (!open_lines) {
>> + spin_lock(&l_mg->free_lock);
>> WARN_ON_ONCE(!test_and_clear_bit(meta_line,
>> &l_mg->meta_bitmap));
>> + spin_unlock(&l_mg->free_lock);
>> pblk_line_replace_data(pblk);
>> } else {
>> + spin_lock(&l_mg->free_lock);
>> /* Allocate next line for preparation */
>> l_mg->data_next = pblk_line_get(pblk);
>> if (l_mg->data_next) {
>> @@ -968,8 +970,8 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
>> l_mg->data_next->type = PBLK_LINETYPE_DATA;
>> is_next = 1;
>> }
>> + spin_unlock(&l_mg->free_lock);
>> }
>> - spin_unlock(&l_mg->free_lock);
>
> Wouldn't the most straight forward solution here to not take the lock?
>
> As pblk is doing all the recovery sequentially during initialization,
> I don't see the
> reason for grabbing the lock.
>
We start doing GC as we recover and, even though right now there is no
interference, the code might change. For such a little change, I would
rather maintain lock consistency than being smart about where we can
avoid locking - specially when this is not the fast path.
Javier
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