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lightnvm: pblk: remove I/O dependency on write path 

pblk schedules user I/O, metadata I/O and erases on the write path in
order to minimize collisions at the media level. Until now, there has
been a dependency between user and metadata I/Os that could lead to a
deadlock as both take the per-LUN semaphore to schedule submission.

This path removes this dependency and guarantees forward progress at a
per I/O granurality.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Javier González 2017-10-13 14:46:25 +02:00 committed by Jens Axboe
parent 0f9248cf1e
commit 1e82123da6
1 changed files with 65 additions and 80 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

145
drivers/lightnvm/pblk-write.c
View File

@ -220,15 +220,16 @@ static int pblk_alloc_w_rq(struct pblk *pblk, struct nvm_rq *rqd,
}
static int pblk_setup_w_rq(struct pblk *pblk, struct nvm_rq *rqd,
struct pblk_c_ctx *c_ctx, struct ppa_addr *erase_ppa)
struct ppa_addr *erase_ppa)
{
struct pblk_line_meta *lm = &pblk->lm;
struct pblk_line *e_line = pblk_line_get_erase(pblk);
struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
unsigned int valid = c_ctx->nr_valid;
unsigned int padded = c_ctx->nr_padded;
unsigned int nr_secs = valid + padded;
unsigned long *lun_bitmap;
int ret = 0;
int ret;
lun_bitmap = kzalloc(lm->lun_bitmap_len, GFP_KERNEL);
if (!lun_bitmap)
@ -294,55 +295,6 @@ static int pblk_calc_secs_to_sync(struct pblk *pblk, unsigned int secs_avail,
return secs_to_sync;
}
static inline int pblk_valid_meta_ppa(struct pblk *pblk,
struct pblk_line *meta_line,
struct ppa_addr *ppa_list, int nr_ppas)
{
struct nvm_tgt_dev *dev = pblk->dev;
struct nvm_geo *geo = &dev->geo;
struct pblk_line *data_line;
struct ppa_addr ppa, ppa_opt;
u64 paddr;
int i;
data_line = &pblk->lines[pblk_dev_ppa_to_line(ppa_list[0])];
paddr = pblk_lookup_page(pblk, meta_line);
ppa = addr_to_gen_ppa(pblk, paddr, 0);
if (test_bit(pblk_ppa_to_pos(geo, ppa), data_line->blk_bitmap))
return 1;
/* Schedule a metadata I/O that is half the distance from the data I/O
* with regards to the number of LUNs forming the pblk instance. This
* balances LUN conflicts across every I/O.
*
* When the LUN configuration changes (e.g., due to GC), this distance
* can align, which would result on a LUN deadlock. In this case, modify
* the distance to not be optimal, but allow metadata I/Os to succeed.
*/
ppa_opt = addr_to_gen_ppa(pblk, paddr + data_line->meta_distance, 0);
if (unlikely(ppa_opt.ppa == ppa.ppa)) {
data_line->meta_distance--;
return 0;
}
for (i = 0; i < nr_ppas; i += pblk->min_write_pgs)
if (ppa_list[i].g.ch == ppa_opt.g.ch &&
ppa_list[i].g.lun == ppa_opt.g.lun)
return 1;
if (test_bit(pblk_ppa_to_pos(geo, ppa_opt), data_line->blk_bitmap)) {
for (i = 0; i < nr_ppas; i += pblk->min_write_pgs)
if (ppa_list[i].g.ch == ppa.g.ch &&
ppa_list[i].g.lun == ppa.g.lun)
return 0;
return 1;
}
return 0;
}
int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)
{
struct nvm_tgt_dev *dev = pblk->dev;
@ -421,8 +373,44 @@ fail_free_rqd:
return ret;
}
static int pblk_sched_meta_io(struct pblk *pblk, struct ppa_addr *prev_list,
int prev_n)
static inline bool pblk_valid_meta_ppa(struct pblk *pblk,
struct pblk_line *meta_line,
struct nvm_rq *data_rqd)
{
struct nvm_tgt_dev *dev = pblk->dev;
struct nvm_geo *geo = &dev->geo;
struct pblk_c_ctx *data_c_ctx = nvm_rq_to_pdu(data_rqd);
struct pblk_line *data_line = pblk_line_get_data(pblk);
struct ppa_addr ppa, ppa_opt;
u64 paddr;
int pos_opt;
/* Schedule a metadata I/O that is half the distance from the data I/O
* with regards to the number of LUNs forming the pblk instance. This
* balances LUN conflicts across every I/O.
*
* When the LUN configuration changes (e.g., due to GC), this distance
* can align, which would result on metadata and data I/Os colliding. In
* this case, modify the distance to not be optimal, but move the
* optimal in the right direction.
*/
paddr = pblk_lookup_page(pblk, meta_line);
ppa = addr_to_gen_ppa(pblk, paddr, 0);
ppa_opt = addr_to_gen_ppa(pblk, paddr + data_line->meta_distance, 0);
pos_opt = pblk_ppa_to_pos(geo, ppa_opt);
if (test_bit(pos_opt, data_c_ctx->lun_bitmap) ||
test_bit(pos_opt, data_line->blk_bitmap))
return true;
if (unlikely(pblk_ppa_comp(ppa_opt, ppa)))
data_line->meta_distance--;
return false;
}
static struct pblk_line *pblk_should_submit_meta_io(struct pblk *pblk,
struct nvm_rq *data_rqd)
{
struct pblk_line_meta *lm = &pblk->lm;
struct pblk_line_mgmt *l_mg = &pblk->l_mg;
@ -432,57 +420,45 @@ static int pblk_sched_meta_io(struct pblk *pblk, struct ppa_addr *prev_list,
retry:
if (list_empty(&l_mg->emeta_list)) {
spin_unlock(&l_mg->close_lock);
return 0;
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;
spin_unlock(&l_mg->close_lock);
if (!pblk_valid_meta_ppa(pblk, meta_line, prev_list, prev_n))
return 0;
if (!pblk_valid_meta_ppa(pblk, meta_line, data_rqd))
return NULL;
return pblk_submit_meta_io(pblk, meta_line);
return meta_line;
}
static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd)
{
struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
struct ppa_addr erase_ppa;
struct pblk_line *meta_line;
int err;
ppa_set_empty(&erase_ppa);
/* Assign lbas to ppas and populate request structure */
err = pblk_setup_w_rq(pblk, rqd, c_ctx, &erase_ppa);
err = pblk_setup_w_rq(pblk, rqd, &erase_ppa);
if (err) {
pr_err("pblk: could not setup write request: %d\n", err);
return NVM_IO_ERR;
}
if (likely(ppa_empty(erase_ppa))) {
/* Submit metadata write for previous data line */
err = pblk_sched_meta_io(pblk, rqd->ppa_list, rqd->nr_ppas);
if (err) {
pr_err("pblk: metadata I/O submission failed: %d", err);
return NVM_IO_ERR;
}
meta_line = pblk_should_submit_meta_io(pblk, rqd);
/* Submit data write for current data line */
err = pblk_submit_io(pblk, rqd);
if (err) {
pr_err("pblk: data I/O submission failed: %d\n", err);
return NVM_IO_ERR;
}
} else {
/* Submit data write for current data line */
err = pblk_submit_io(pblk, rqd);
if (err) {
pr_err("pblk: data I/O submission failed: %d\n", err);
return NVM_IO_ERR;
}
/* Submit data write for current data line */
err = pblk_submit_io(pblk, rqd);
if (err) {
pr_err("pblk: data I/O submission failed: %d\n", err);
return NVM_IO_ERR;
}
/* Submit available erase for next data line */
if (!ppa_empty(erase_ppa)) {
/* Submit erase for next data line */
if (pblk_blk_erase_async(pblk, erase_ppa)) {
struct pblk_line *e_line = pblk_line_get_erase(pblk);
struct nvm_tgt_dev *dev = pblk->dev;
@ -495,6 +471,15 @@ static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd)
}
}
if (meta_line) {
/* Submit metadata write for previous data line */
err = pblk_submit_meta_io(pblk, meta_line);
if (err) {
pr_err("pblk: metadata I/O submission failed: %d", err);
return NVM_IO_ERR;
}
}
return NVM_IO_OK;
}