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>

diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index f2e846fe9242ac55486a69f495b5dbae0d7d063e..6c1cafafef532c8406ac0b763a9d154a1afdb190 100644 (file)
--- 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;
 }