lightnvm: make rrpc_map_page call nvm_get_blk outside locks

The nvm_get_blk() function is called with rlun->lock held. This is ok
when the media manager implementation doesn't go out of its atomic
context. However, if a media manager persists its metadata, and
guarantees that the block is given to the target, this is no longer
a viable approach. Therefore, clean up the flow of rrpc_map_page,
and make sure that nvm_get_blk() is called without any locks acquired.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

2 files changed, 66 insertions, 43 deletions

diff --git a/drivers/lightnvm/rrpc.c b/drivers/lightnvm/rrpc.c
index fa8d5be2987c..fa1ab0421489 100644
--- a/drivers/lightnvm/rrpc.c
+++ b/drivers/lightnvm/rrpc.c
@@ -175,18 +175,17 @@ static struct ppa_addr rrpc_ppa_to_gaddr(struct nvm_dev *dev, u64 addr)
 }
 
 /* requires lun->lock taken */
-static void rrpc_set_lun_cur(struct rrpc_lun *rlun, struct rrpc_block *rblk)
+static void rrpc_set_lun_cur(struct rrpc_lun *rlun, struct rrpc_block *new_rblk,
+                                                struct rrpc_block **cur_rblk)
 {
         struct rrpc *rrpc = rlun->rrpc;
 
-        BUG_ON(!rblk);
-
-        if (rlun->cur) {
-                spin_lock(&rlun->cur->lock);
-                WARN_ON(!block_is_full(rrpc, rlun->cur));
-                spin_unlock(&rlun->cur->lock);
+        if (*cur_rblk) {
+                spin_lock(&(*cur_rblk)->lock);
+                WARN_ON(!block_is_full(rrpc, *cur_rblk));
+                spin_unlock(&(*cur_rblk)->lock);
         }
-        rlun->cur = rblk;
+        *cur_rblk = new_rblk;
 }
 
 static struct rrpc_block *rrpc_get_blk(struct rrpc *rrpc, struct rrpc_lun *rlun,
@@ -577,21 +576,20 @@ out:
         return addr;
 }
 
-/* Simple round-robin Logical to physical address translation.
- *
- * Retrieve the mapping using the active append point. Then update the ap for
- * the next write to the disk.
+/* Map logical address to a physical page. The mapping implements a round robin
+ * approach and allocates a page from the next lun available.
  *
- * Returns rrpc_addr with the physical address and block. Remember to return to
- * rrpc->addr_cache when request is finished.
+ * Returns rrpc_addr with the physical address and block. Returns NULL if no
+ * blocks in the next rlun are available.
  */
 static struct rrpc_addr *rrpc_map_page(struct rrpc *rrpc, sector_t laddr,
                                                                 int is_gc)
 {
         struct rrpc_lun *rlun;
-        struct rrpc_block *rblk;
+        struct rrpc_block *rblk, **cur_rblk;
         struct nvm_lun *lun;
         u64 paddr;
+        int gc_force = 0;
 
         rlun = rrpc_get_lun_rr(rrpc, is_gc);
         lun = rlun->parent;
@@ -599,41 +597,65 @@ static struct rrpc_addr *rrpc_map_page(struct rrpc *rrpc, sector_t laddr,
         if (!is_gc && lun->nr_free_blocks < rrpc->nr_luns * 4)
                 return NULL;
 
-        spin_lock(&rlun->lock);
+        /*
+         * page allocation steps:
+         * 1. Try to allocate new page from current rblk
+         * 2a. If succeed, proceed to map it in and return
+         * 2b. If fail, first try to allocate a new block from media manger,
+         *     and then retry step 1. Retry until the normal block pool is
+         *     exhausted.
+         * 3. If exhausted, and garbage collector is requesting the block,
+         *    go to the reserved block and retry step 1.
+         *    In the case that this fails as well, or it is not GC
+         *    requesting, report not able to retrieve a block and let the
+         *    caller handle further processing.
+         */
 
+        spin_lock(&rlun->lock);
+        cur_rblk = &rlun->cur;
         rblk = rlun->cur;
 retry:
         paddr = rrpc_alloc_addr(rrpc, rblk);
 
-        if (paddr == ADDR_EMPTY) {
-                rblk = rrpc_get_blk(rrpc, rlun, 0);
-                if (rblk) {
-                        rrpc_set_lun_cur(rlun, rblk);
-                        goto retry;
-                }
+        if (paddr != ADDR_EMPTY)
+                goto done;
 
-                if (is_gc) {
-                        /* retry from emergency gc block */
-                        paddr = rrpc_alloc_addr(rrpc, rlun->gc_cur);
-                        if (paddr == ADDR_EMPTY) {
-                                rblk = rrpc_get_blk(rrpc, rlun, 1);
-                                if (!rblk) {
-                                        pr_err("rrpc: no more blocks");
-                                        goto err;
-                                }
-
-                                rlun->gc_cur = rblk;
-                                paddr = rrpc_alloc_addr(rrpc, rlun->gc_cur);
-                        }
-                        rblk = rlun->gc_cur;
-                }
+        if (!list_empty(&rlun->wblk_list)) {
+new_blk:
+                rblk = list_first_entry(&rlun->wblk_list, struct rrpc_block,
+                                                                        prio);
+                rrpc_set_lun_cur(rlun, rblk, cur_rblk);
+                list_del(&rblk->prio);
+                goto retry;
+        }
+        spin_unlock(&rlun->lock);
+
+        rblk = rrpc_get_blk(rrpc, rlun, gc_force);
+        if (rblk) {
+                spin_lock(&rlun->lock);
+                list_add_tail(&rblk->prio, &rlun->wblk_list);
+                /*
+                 * another thread might already have added a new block,
+                 * Therefore, make sure that one is used, instead of the
+                 * one just added.
+                 */
+                goto new_blk;
+        }
+
+        if (unlikely(is_gc) && !gc_force) {
+                /* retry from emergency gc block */
+                cur_rblk = &rlun->gc_cur;
+                rblk = rlun->gc_cur;
+                gc_force = 1;
+                spin_lock(&rlun->lock);
+                goto retry;
         }
 
+        pr_err("rrpc: failed to allocate new block\n");
+        return NULL;
+done:
         spin_unlock(&rlun->lock);
         return rrpc_update_map(rrpc, laddr, rblk, paddr);
-err:
-        spin_unlock(&rlun->lock);
-        return NULL;
 }
 
 static void rrpc_run_gc(struct rrpc *rrpc, struct rrpc_block *rblk)
@@ -1177,6 +1199,7 @@ static int rrpc_luns_init(struct rrpc *rrpc, int lun_begin, int lun_end)
 
                 rlun->rrpc = rrpc;
                 INIT_LIST_HEAD(&rlun->prio_list);
+                INIT_LIST_HEAD(&rlun->wblk_list);
 
                 INIT_WORK(&rlun->ws_gc, rrpc_lun_gc);
                 spin_lock_init(&rlun->lock);
@@ -1317,14 +1340,13 @@ static int rrpc_luns_configure(struct rrpc *rrpc)
                 rblk = rrpc_get_blk(rrpc, rlun, 0);
                 if (!rblk)
                         goto err;
-
-                rrpc_set_lun_cur(rlun, rblk);
+                rrpc_set_lun_cur(rlun, rblk, &rlun->cur);
 
                 /* Emergency gc block */
                 rblk = rrpc_get_blk(rrpc, rlun, 1);
                 if (!rblk)
                         goto err;
-                rlun->gc_cur = rblk;
+                rrpc_set_lun_cur(rlun, rblk, &rlun->gc_cur);
         }
 
         return 0;
diff --git a/drivers/lightnvm/rrpc.h b/drivers/lightnvm/rrpc.h
index 448e39a9c515..5e87d52cb983 100644
--- a/drivers/lightnvm/rrpc.h
+++ b/drivers/lightnvm/rrpc.h
@@ -76,6 +76,7 @@ struct rrpc_lun {
         struct rrpc_block *blocks;      /* Reference to block allocation */
 
         struct list_head prio_list;     /* Blocks that may be GC'ed */
+        struct list_head wblk_list;     /* Queued blocks to be written to */
 
         struct work_struct ws_gc;