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SubjectRe: [PATCH] lightnvm: pblk: take write semaphore on metadata
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> On 3 Aug 2018, at 14.45, Matias Bjørling <mb@lightnvm.io> wrote:
>
> On 08/03/2018 02:05 PM, Javier González wrote:
>> pblk guarantees write ordering at a chunk level through a per open chunk
>> semaphore. At this point, since we only have an open I/O stream for both
>> user and GC data, the semaphore is per parallel unit.
>> Since metadata I/O is synchronous, the semaphore is not needed as
>> ordering is guaranteed. However, if the metadata scheme changes or
>> multiple streams are open, this guarantee might not be preserved.
>> This patch makes sure that all writes go through the semaphore, even for
>> synchronous I/O. This is consistent with pblk's write I/O model. It also
>> simplifies maintenance since changes in the metdatada scheme could cause
>> ordering issues.
>> Signed-off-by: Javier González <javier@cnexlabs.com>
>> ---
>> drivers/lightnvm/pblk-core.c | 14 ++++++++++++--
>> drivers/lightnvm/pblk.h | 1 +
>> 2 files changed, 13 insertions(+), 2 deletions(-)
>> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
>> index 00984b486fea..160b54d26bfa 100644
>> --- a/drivers/lightnvm/pblk-core.c
>> +++ b/drivers/lightnvm/pblk-core.c
>> @@ -493,6 +493,16 @@ int pblk_submit_io_sync(struct pblk *pblk, struct nvm_rq *rqd)
>> return nvm_submit_io_sync(dev, rqd);
>> }
>> +int pblk_submit_io_sync_sem(struct pblk *pblk, struct nvm_rq *rqd)
>> +{
>> + if (rqd->opcode != NVM_OP_PWRITE)
>> + pblk_submit_io_sync(pblk, rqd);
>> +
>
> Why should the write be issued twice?
>

It is the read that is sent twice, that's why it does not fail. Rebased
the patch manually and messed up... should be return... I'll send a V2.

Javier
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