1 files changed, 94 insertions, 21 deletions

diff --git a/drivers/md/persistent-data/dm-space-map-metadata.c b/drivers/md/persistent-data/dm-space-map-metadata.c
index 536782e3bcb7..786b689bdfc7 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.c
+++ b/drivers/md/persistent-data/dm-space-map-metadata.c
@@ -91,6 +91,69 @@ struct block_op {
         dm_block_t block;
 };
 
+struct bop_ring_buffer {
+        unsigned begin;
+        unsigned end;
+        struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
+};
+
+static void brb_init(struct bop_ring_buffer *brb)
+{
+        brb->begin = 0;
+        brb->end = 0;
+}
+
+static bool brb_empty(struct bop_ring_buffer *brb)
+{
+        return brb->begin == brb->end;
+}
+
+static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
+{
+        unsigned r = old + 1;
+        return (r >= (sizeof(brb->bops) / sizeof(*brb->bops))) ? 0 : r;
+}
+
+static int brb_push(struct bop_ring_buffer *brb,
+                    enum block_op_type type, dm_block_t b)
+{
+        struct block_op *bop;
+        unsigned next = brb_next(brb, brb->end);
+
+        /*
+         * We don't allow the last bop to be filled, this way we can
+         * differentiate between full and empty.
+         */
+        if (next == brb->begin)
+                return -ENOMEM;
+
+        bop = brb->bops + brb->end;
+        bop->type = type;
+        bop->block = b;
+
+        brb->end = next;
+
+        return 0;
+}
+
+static int brb_pop(struct bop_ring_buffer *brb, struct block_op *result)
+{
+        struct block_op *bop;
+
+        if (brb_empty(brb))
+                return -ENODATA;
+
+        bop = brb->bops + brb->begin;
+        result->type = bop->type;
+        result->block = bop->block;
+
+        brb->begin = brb_next(brb, brb->begin);
+
+        return 0;
+}
+
+/*----------------------------------------------------------------*/
+
 struct sm_metadata {
         struct dm_space_map sm;
 
@@ -101,25 +164,20 @@ struct sm_metadata {
 
         unsigned recursion_count;
         unsigned allocated_this_transaction;
-        unsigned nr_uncommitted;
-        struct block_op uncommitted[MAX_RECURSIVE_ALLOCATIONS];
+        struct bop_ring_buffer uncommitted;
 
         struct threshold threshold;
 };
 
 static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
 {
-        struct block_op *op;
+        int r = brb_push(&smm->uncommitted, type, b);
 
-        if (smm->nr_uncommitted == MAX_RECURSIVE_ALLOCATIONS) {
+        if (r) {
                 DMERR("too many recursive allocations");
                 return -ENOMEM;
         }
 
-        op = smm->uncommitted + smm->nr_uncommitted++;
-        op->type = type;
-        op->block = b;
-
         return 0;
 }
 
@@ -158,11 +216,17 @@ static int out(struct sm_metadata *smm)
                 return -ENOMEM;
         }
 
-        if (smm->recursion_count == 1 && smm->nr_uncommitted) {
-                while (smm->nr_uncommitted && !r) {
-                        smm->nr_uncommitted--;
-                        r = commit_bop(smm, smm->uncommitted +
-                                       smm->nr_uncommitted);
+        if (smm->recursion_count == 1) {
+                while (!brb_empty(&smm->uncommitted)) {
+                        struct block_op bop;
+
+                        r = brb_pop(&smm->uncommitted, &bop);
+                        if (r) {
+                                DMERR("bug in bop ring buffer");
+                                break;
+                        }
+
+                        r = commit_bop(smm, &bop);
                         if (r)
                                 break;
                 }
@@ -217,7 +281,8 @@ static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
 static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
                                  uint32_t *result)
 {
-        int r, i;
+        int r;
+        unsigned i;
         struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
         unsigned adjustment = 0;
 
@@ -225,8 +290,10 @@ static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
          * We may have some uncommitted adjustments to add.  This list
          * should always be really short.
          */
-        for (i = 0; i < smm->nr_uncommitted; i++) {
-                struct block_op *op = smm->uncommitted + i;
+        for (i = smm->uncommitted.begin;
+             i != smm->uncommitted.end;
+             i = brb_next(&smm->uncommitted, i)) {
+                struct block_op *op = smm->uncommitted.bops + i;
 
                 if (op->block != b)
                         continue;
@@ -254,7 +321,8 @@ static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
 static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
                                               dm_block_t b, int *result)
 {
-        int r, i, adjustment = 0;
+        int r, adjustment = 0;
+        unsigned i;
         struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
         uint32_t rc;
 
@@ -262,8 +330,11 @@ static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
          * We may have some uncommitted adjustments to add.  This list
          * should always be really short.
          */
-        for (i = 0; i < smm->nr_uncommitted; i++) {
-                struct block_op *op = smm->uncommitted + i;
+        for (i = smm->uncommitted.begin;
+             i != smm->uncommitted.end;
+             i = brb_next(&smm->uncommitted, i)) {
+
+                struct block_op *op = smm->uncommitted.bops + i;
 
                 if (op->block != b)
                         continue;
@@ -671,7 +742,7 @@ int dm_sm_metadata_create(struct dm_space_map *sm,
         smm->begin = superblock + 1;
         smm->recursion_count = 0;
         smm->allocated_this_transaction = 0;
-        smm->nr_uncommitted = 0;
+        brb_init(&smm->uncommitted);
         threshold_init(&smm->threshold);
 
         memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));
@@ -680,6 +751,8 @@ int dm_sm_metadata_create(struct dm_space_map *sm,
         if (r)
                 return r;
 
+        if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
+                nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
         r = sm_ll_extend(&smm->ll, nr_blocks);
         if (r)
                 return r;
@@ -713,7 +786,7 @@ int dm_sm_metadata_open(struct dm_space_map *sm,
         smm->begin = 0;
         smm->recursion_count = 0;
         smm->allocated_this_transaction = 0;
-        smm->nr_uncommitted = 0;
+        brb_init(&smm->uncommitted);
         threshold_init(&smm->threshold);
 
         memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));