feat(blobstore): add function to return max growable size of the blobstore

Signed-off-by: Abhilash Shetty <[email protected]>

Author: abhilashshetty04

include/spdk/blob.h

@@ -494,6 +494,16 @@ uint64_t spdk_bs_get_md_len(struct spdk_blob_store *bs);
  */
 uint64_t spdk_bs_get_used_md(struct spdk_blob_store *bs);
 
+/**
+ * Get the maximum growable size of blobstore. floored to GiB value, in bytes
+ *
+ * \param bs blobstore to query.
+ *
+ * \return the maximum growable size in bytes
+ */
+uint64_t
+spdk_bs_get_max_growable_size(struct spdk_blob_store *bs);
+
 /**
  * Get the blob id.
  *

lib/blob/blobstore.c

@@ -6185,6 +6185,25 @@ spdk_bs_get_used_md(struct spdk_blob_store *bs)
 	return res;
 }
 
+uint64_t
+spdk_bs_get_max_growable_size(struct spdk_blob_store *bs)
+{
+    uint64_t max_used_cluster_mask, max_growable_size;
+
+	/* Calculate max number of pages for used_cluster_mask. This is immutable.
+     */
+    max_used_cluster_mask = spdk_divide_round_up(sizeof(struct spdk_bs_md_mask) +
+                    spdk_divide_round_up(bs->md_len, 8),
+                    SPDK_BS_PAGE_SIZE);
+
+    /* max growable size = Total number of bits * cluster size */
+    max_growable_size = max_used_cluster_mask * (SPDK_BS_PAGE_SIZE - sizeof(struct spdk_bs_md_mask)) * 8 * bs->cluster_sz;
+
+	/* Floor to the nearest GiB, in bytes */
+    max_growable_size &= ~((1ULL << 30) - 1);
+    return max_growable_size;
+}
+
 static int
 bs_register_md_thread(struct spdk_blob_store *bs)
 {