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>

1 files changed, 65 insertions, 80 deletions

diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index f2e846fe9242..6c1cafafef53 100644
--- a/drivers/lightnvm/pblk-write.c
+++ b/drivers/lightnvm/pblk-write.c
@@ -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;
 }