lightnvm: pblk: set conservative threshold for user writes

In a worst-case scenario (random writes), OP% of sectors
in each line will be invalid, and we will then need
to move data out of 100/OP% lines to free a single line.

So, to prevent the possibility of running out of lines,
temporarily block user writes when there is less than
100/OP% free lines.

Also ensure that pblk creation does not produce instances
with insufficient over provisioning.

Insufficient over-provising is not a problem on real hardware,
but often an issue when running QEMU simulations (with few lines).
100 lines is enough to create a sane instance with the standard
(11%) over provisioning.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 13822594647c112f479ebe3693c2e57b0cd2d2cb..f083130d9920377698f034b85ace268cb381b1bf 100644 (file)
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -635,7 +635,7 @@ static unsigned int calc_emeta_len(struct pblk *pblk)
        return (lm->emeta_len[1] + lm->emeta_len[2] + lm->emeta_len[3]);
 }
 
-static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
+static int pblk_set_provision(struct pblk *pblk, int nr_free_chks)
 {
        struct nvm_tgt_dev *dev = pblk->dev;
        struct pblk_line_mgmt *l_mg = &pblk->l_mg;
@@ -643,23 +643,41 @@ static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
        struct nvm_geo *geo = &dev->geo;
        sector_t provisioned;
        int sec_meta, blk_meta;
+       int minimum;
 
        if (geo->op == NVM_TARGET_DEFAULT_OP)
                pblk->op = PBLK_DEFAULT_OP;
        else
                pblk->op = geo->op;
 
-       provisioned = nr_free_blks;
+       minimum = pblk_get_min_chks(pblk);
+       provisioned = nr_free_chks;
        provisioned *= (100 - pblk->op);
        sector_div(provisioned, 100);
 
-       pblk->op_blks = nr_free_blks - provisioned;
+       if ((nr_free_chks - provisioned) < minimum) {
+               if (geo->op != NVM_TARGET_DEFAULT_OP) {
+                       pblk_err(pblk, "OP too small to create a sane instance\n");
+                       return -EINTR;
+               }
+
+               /* If the user did not specify an OP value, and PBLK_DEFAULT_OP
+                * is not enough, calculate and set sane value
+                */
+
+               provisioned = nr_free_chks - minimum;
+               pblk->op =  (100 * minimum) / nr_free_chks;
+               pblk_info(pblk, "Default OP insufficient, adjusting OP to %d\n",
+                               pblk->op);
+       }
+
+       pblk->op_blks = nr_free_chks - provisioned;
 
        /* Internally pblk manages all free blocks, but all calculations based
         * on user capacity consider only provisioned blocks
         */
-       pblk->rl.total_blocks = nr_free_blks;
-       pblk->rl.nr_secs = nr_free_blks * geo->clba;
+       pblk->rl.total_blocks = nr_free_chks;
+       pblk->rl.nr_secs = nr_free_chks * geo->clba;
 
        /* Consider sectors used for metadata */
        sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;
@@ -667,8 +685,10 @@ static void pblk_set_provision(struct pblk *pblk, long nr_free_blks)
 
        pblk->capacity = (provisioned - blk_meta) * geo->clba;
 
-       atomic_set(&pblk->rl.free_blocks, nr_free_blks);
-       atomic_set(&pblk->rl.free_user_blocks, nr_free_blks);
+       atomic_set(&pblk->rl.free_blocks, nr_free_chks);
+       atomic_set(&pblk->rl.free_user_blocks, nr_free_chks);
+
+       return 0;
 }
 
 static int pblk_setup_line_meta_chk(struct pblk *pblk, struct pblk_line *line,
@@ -984,7 +1004,7 @@ static int pblk_lines_init(struct pblk *pblk)
        struct pblk_line_mgmt *l_mg = &pblk->l_mg;
        struct pblk_line *line;
        void *chunk_meta;
-       long nr_free_chks = 0;
+       int nr_free_chks = 0;
        int i, ret;
 
        ret = pblk_line_meta_init(pblk);
@@ -1031,7 +1051,9 @@ static int pblk_lines_init(struct pblk *pblk)
                goto fail_free_lines;
        }
 
-       pblk_set_provision(pblk, nr_free_chks);
+       ret = pblk_set_provision(pblk, nr_free_chks);
+       if (ret)
+               goto fail_free_lines;
 
        vfree(chunk_meta);
        return 0;

diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
index db55a1c89997edd666f1705184e56a9a944587b3..76116d5f78e46ca7484f5dd49071abac6b2a8bdf 100644 (file)
--- a/drivers/lightnvm/pblk-rl.c
+++ b/drivers/lightnvm/pblk-rl.c
@@ -214,11 +214,10 @@ void pblk_rl_init(struct pblk_rl *rl, int budget)
        struct nvm_geo *geo = &dev->geo;
        struct pblk_line_mgmt *l_mg = &pblk->l_mg;
        struct pblk_line_meta *lm = &pblk->lm;
-       int min_blocks = lm->blk_per_line * PBLK_GC_RSV_LINE;
        int sec_meta, blk_meta;
-
        unsigned int rb_windows;
 
+
        /* Consider sectors used for metadata */
        sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;
        blk_meta = DIV_ROUND_UP(sec_meta, geo->clba);
@@ -226,7 +225,7 @@ void pblk_rl_init(struct pblk_rl *rl, int budget)
        rl->high = pblk->op_blks - blk_meta - lm->blk_per_line;
        rl->high_pw = get_count_order(rl->high);
 
-       rl->rsv_blocks = min_blocks;
+       rl->rsv_blocks = pblk_get_min_chks(pblk);
 
        /* This will always be a power-of-2 */
        rb_windows = budget / NVM_MAX_VLBA;

diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
index f415aae600c859fa340560d5e66cfd6c8d762595..e5b88a25d4d6e2a1ab85a1c92fb37d0519929d60 100644 (file)
--- a/drivers/lightnvm/pblk.h
+++ b/drivers/lightnvm/pblk.h
@@ -905,7 +905,6 @@ int pblk_recov_check_emeta(struct pblk *pblk, struct line_emeta *emeta);
 #define PBLK_GC_MAX_READERS 8  /* Max number of outstanding GC reader jobs */
 #define PBLK_GC_RQ_QD 128      /* Queue depth for inflight GC requests */
 #define PBLK_GC_L_QD 4         /* Queue depth for inflight GC lines */
-#define PBLK_GC_RSV_LINE 1     /* Reserved lines for GC */
 
 int pblk_gc_init(struct pblk *pblk);
 void pblk_gc_exit(struct pblk *pblk, bool graceful);
@@ -1370,4 +1369,15 @@ static inline char *pblk_disk_name(struct pblk *pblk)
 
        return disk->disk_name;
 }
+
+static inline unsigned int pblk_get_min_chks(struct pblk *pblk)
+{
+       struct pblk_line_meta *lm = &pblk->lm;
+       /* In a worst-case scenario every line will have OP invalid sectors.
+        * We will then need a minimum of 1/OP lines to free up a single line
+        */
+
+       return DIV_ROUND_UP(100, pblk->op) * lm->blk_per_line;
+
+}
 #endif /* PBLK_H_ */