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Date: Mon, 17 Sep 2018 10:17:02 +0000
From: Javier Gonzalez <javier@...xlabs.com>
To: Matias Bjørling <mb@...htnvm.io>
CC: "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] lightnvm: pblk: retrieve chunk metadata on erase
> On 17 Sep 2018, at 10.26, Matias Bjørling <mb@...htnvm.io> wrote:
>
> On 09/11/2018 01:35 PM, Javier González wrote:
>> On the OCSSD 2.0 spec, the device populates the metadata pointer (if
>> provided) when a chunk is reset. Implement this path in pblk and use it
>> for sanity chunk checks.
>> For 1.2, reset the write pointer and the state on core so that the erase
>> path is transparent to pblk wrt OCSSD version.
>> Signed-off-by: Javier González <javier@...xlabs.com>
>> ---
>> drivers/lightnvm/core.c | 44 ++++++++++++++++++++++++++++++++++++--
>> drivers/lightnvm/pblk-core.c | 51 +++++++++++++++++++++++++++++++++-----------
>> 2 files changed, 80 insertions(+), 15 deletions(-)
>> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
>> index efb976a863d2..dceaae4e795f 100644
>> --- a/drivers/lightnvm/core.c
>> +++ b/drivers/lightnvm/core.c
>> @@ -750,9 +750,40 @@ int nvm_submit_io(struct nvm_tgt_dev *tgt_dev, struct nvm_rq *rqd)
>> }
>> EXPORT_SYMBOL(nvm_submit_io);
>> +/* Take only addresses in generic format */
>> +static void nvm_set_chunk_state_12(struct nvm_dev *dev, struct nvm_rq *rqd)
>> +{
>> + struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
>> + int i;
>> +
>> + for (i = 0; i < rqd->nr_ppas; i++) {
>> + struct ppa_addr ppa;
>> + struct nvm_chk_meta *chunk;
>> +
>> + chunk = ((struct nvm_chk_meta *)rqd->meta_list) + i;
>> +
>> + if (rqd->error)
>> + chunk->state = NVM_CHK_ST_OFFLINE;
>> + else
>> + chunk->state = NVM_CHK_ST_FREE;
>> +
>> + chunk->wp = 0;
>> + chunk->wi = 0;
>> + chunk->type = NVM_CHK_TP_W_SEQ;
>> + chunk->cnlb = dev->geo.clba;
>> +
>> + /* recalculate slba for the chunk */
>> + ppa = ppa_list[i];
>> + ppa.g.pg = ppa.g.pl = ppa.g.sec = 0;
>> +
>> + chunk->slba = generic_to_dev_addr(dev, ppa).ppa;
>> + }
>> +}
>> +
>> int nvm_submit_io_sync(struct nvm_tgt_dev *tgt_dev, struct nvm_rq *rqd)
>> {
>> struct nvm_dev *dev = tgt_dev->parent;
>> + struct nvm_geo *geo = &dev->geo;
>> int ret;
>> if (!dev->ops->submit_io_sync)
>> @@ -765,8 +796,12 @@ int nvm_submit_io_sync(struct nvm_tgt_dev *tgt_dev, struct nvm_rq *rqd)
>> /* In case of error, fail with right address format */
>> ret = dev->ops->submit_io_sync(dev, rqd);
>> +
>> nvm_rq_dev_to_tgt(tgt_dev, rqd);
>> + if (geo->version == NVM_OCSSD_SPEC_12 && rqd->opcode == NVM_OP_ERASE)
>> + nvm_set_chunk_state_12(dev, rqd);
>> +
>> return ret;
>> }
>> EXPORT_SYMBOL(nvm_submit_io_sync);
>> @@ -775,10 +810,15 @@ void nvm_end_io(struct nvm_rq *rqd)
>> {
>> struct nvm_tgt_dev *tgt_dev = rqd->dev;
>> - /* Convert address space */
>> - if (tgt_dev)
>> + if (tgt_dev) {
>> + /* Convert address space */
>> nvm_rq_dev_to_tgt(tgt_dev, rqd);
>> + if (tgt_dev->geo.version == NVM_OCSSD_SPEC_12 &&
>> + rqd->opcode == NVM_OP_ERASE)
>> + nvm_set_chunk_state_12(tgt_dev->parent, rqd);
>> + }
>> +
>> if (rqd->end_io)
>> rqd->end_io(rqd);
>> }
>> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
>> index 417d12b274da..80f0ec756672 100644
>> --- a/drivers/lightnvm/pblk-core.c
>> +++ b/drivers/lightnvm/pblk-core.c
>> @@ -79,7 +79,7 @@ static void __pblk_end_io_erase(struct pblk *pblk, struct nvm_rq *rqd)
>> {
>> struct nvm_tgt_dev *dev = pblk->dev;
>> struct nvm_geo *geo = &dev->geo;
>> - struct nvm_chk_meta *chunk;
>> + struct nvm_chk_meta *chunk, *dev_chunk;
>> struct pblk_line *line;
>> int pos;
>> @@ -89,22 +89,39 @@ static void __pblk_end_io_erase(struct pblk *pblk, struct nvm_rq *rqd)
>> atomic_dec(&line->left_seblks);
>> + /* pblk submits a single erase per command */
>> + dev_chunk = rqd->meta_list;
>> +
>> + if (dev_chunk->slba != chunk->slba || dev_chunk->wp)
>> + print_chunk(pblk, chunk, "corrupted erase chunk", 0);
>> +
>> + memcpy(chunk, dev_chunk, sizeof(struct nvm_chk_meta));
>> +
>> if (rqd->error) {
>> trace_pblk_chunk_reset(pblk_disk_name(pblk),
>> &rqd->ppa_addr, PBLK_CHUNK_RESET_FAILED);
>> - chunk->state = NVM_CHK_ST_OFFLINE;
>> +#ifdef CONFIG_NVM_PBLK_DEBUG
>> + if (chunk->state != NVM_CHK_ST_OFFLINE)
>> + print_chunk(pblk, chunk,
>> + "corrupted erase chunk state", 0);
>> +#endif
>> pblk_mark_bb(pblk, line, rqd->ppa_addr);
>> } else {
>> trace_pblk_chunk_reset(pblk_disk_name(pblk),
>> &rqd->ppa_addr, PBLK_CHUNK_RESET_DONE);
>> - chunk->state = NVM_CHK_ST_FREE;
>> +#ifdef CONFIG_NVM_PBLK_DEBUG
>> + if (chunk->state != NVM_CHK_ST_FREE)
>> + print_chunk(pblk, chunk,
>> + "corrupted erase chunk state", 0);
>> +#endif > }
>> trace_pblk_chunk_state(pblk_disk_name(pblk), &rqd->ppa_addr,
>> chunk->state);
>> + pblk_free_rqd_meta(pblk, rqd);
>> atomic_dec(&pblk->inflight_io);
>> }
>> @@ -952,14 +969,16 @@ int pblk_line_emeta_read(struct pblk *pblk, struct pblk_line *line,
>> return ret;
>> }
>> -static void pblk_setup_e_rq(struct pblk *pblk, struct nvm_rq *rqd,
>> - struct ppa_addr ppa)
>> +static int pblk_setup_e_rq(struct pblk *pblk, struct nvm_rq *rqd,
>> + struct ppa_addr ppa)
>> {
>> rqd->opcode = NVM_OP_ERASE;
>> rqd->ppa_addr = ppa;
>> rqd->nr_ppas = 1;
>> rqd->is_seq = 1;
>> rqd->bio = NULL;
>> +
>> + return pblk_alloc_rqd_meta(pblk, rqd);
>> }
>> static int pblk_blk_erase_sync(struct pblk *pblk, struct ppa_addr ppa)
>> @@ -967,10 +986,12 @@ static int pblk_blk_erase_sync(struct pblk *pblk, struct ppa_addr ppa)
>> struct nvm_rq rqd = {NULL};
>> int ret;
>> + ret = pblk_setup_e_rq(pblk, &rqd, ppa);
>> + if (ret)
>> + return ret;
>> +
>> trace_pblk_chunk_reset(pblk_disk_name(pblk), &ppa,
>> - PBLK_CHUNK_RESET_START);
>> -
>> - pblk_setup_e_rq(pblk, &rqd, ppa);
>> + PBLK_CHUNK_RESET_START);
>> /* The write thread schedules erases so that it minimizes disturbances
>> * with writes. Thus, there is no need to take the LUN semaphore.
>> @@ -1774,11 +1795,15 @@ void pblk_line_put_wq(struct kref *ref)
>> int pblk_blk_erase_async(struct pblk *pblk, struct ppa_addr ppa)
>> {
>> struct nvm_rq *rqd;
>> - int err;
>> + int ret;
>> rqd = pblk_alloc_rqd(pblk, PBLK_ERASE);
>> - pblk_setup_e_rq(pblk, rqd, ppa);
>> + ret = pblk_setup_e_rq(pblk, rqd, ppa);
>> + if (ret) {
>> + pblk_free_rqd(pblk, rqd, PBLK_ERASE);
>> + return ret;
>> + }
>> rqd->end_io = pblk_end_io_erase;
>> rqd->private = pblk;
>> @@ -1789,8 +1814,8 @@ int pblk_blk_erase_async(struct pblk *pblk, struct ppa_addr ppa)
>> /* The write thread schedules erases so that it minimizes disturbances
>> * with writes. Thus, there is no need to take the LUN semaphore.
>> */
>> - err = pblk_submit_io(pblk, rqd);
>> - if (err) {
>> + ret = pblk_submit_io(pblk, rqd);
>> + if (ret) {
>> struct nvm_tgt_dev *dev = pblk->dev;
>> struct nvm_geo *geo = &dev->geo;
>> @@ -1799,7 +1824,7 @@ int pblk_blk_erase_async(struct pblk *pblk, struct ppa_addr ppa)
>> pblk_ppa_to_pos(geo, ppa));
>> }
>> - return err;
>> + return ret;
>> }
>> struct pblk_line *pblk_line_get_data(struct pblk *pblk)
>
> I'll lean towards not taking this patch. The usecase adds extra logic,
> overhead, complexity, and its only usecase for debugging.
>
> I am not an advocate of defensive coding in the fast path. For
> example, if an SLBA is inequal with the chunk slba, the drive is
> buggy, and does not behave according to the spec. and therefore does
> not warrant the checks. These type of bugs can be caught in the
> general drive testing suite.
The use case for this patch is to retrieve the wear-leveling information
and the CNLB, which only the drive knows about. Also, this will help
removing the bitmap metadata per line and maintain a per-chunk metadata
instead, reusing the chunk structure retrieved on erase. I want to have
this in before pushing the rest of the patches as they will be depending
on it.
As for the checks, they are sanity that I believe do not hurt, but I'm
ok with removing them (or putting them under debug flags).
Javier
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