+/**
+ * Policy to grow ZFS block size by write pattern.
+ * For sequential write, it grows block size gradually until it reaches the
+ * maximum blocksize the dataset can support. Otherwise, it will pick a
+ * a block size by the writing region of this I/O.
+ */
+static int osd_grow_blocksize(struct osd_object *obj, struct osd_thandle *oh,
+ uint64_t start, uint64_t end)
+{
+ struct osd_device *osd = osd_obj2dev(obj);
+ dmu_buf_impl_t *db = (dmu_buf_impl_t *)obj->oo_db;
+ dnode_t *dn;
+ uint32_t blksz;
+ int rc = 0;
+
+ ENTRY;
+
+ DB_DNODE_ENTER(db);
+ dn = DB_DNODE(db);
+
+ if (dn->dn_maxblkid > 0) /* can't change block size */
+ GOTO(out, rc);
+
+ if (dn->dn_datablksz >= osd->od_max_blksz)
+ GOTO(out, rc);
+
+ down_write(&obj->oo_guard);
+
+ blksz = dn->dn_datablksz;
+ if (blksz >= osd->od_max_blksz) /* check again after grabbing lock */
+ GOTO(out_unlock, rc);
+
+ /* now ZFS can support up to 16MB block size, and if the write
+ * is sequential, it just increases the block size gradually */
+ if (start <= blksz) { /* sequential */
+ blksz = (uint32_t)min_t(uint64_t, osd->od_max_blksz, end);
+ } else { /* sparse, pick a block size by write region */
+ blksz = (uint32_t)min_t(uint64_t, osd->od_max_blksz,
+ end - start);
+ }
+
+ if (!is_power_of_2(blksz))
+ blksz = size_roundup_power2(blksz);
+
+ if (blksz > dn->dn_datablksz) {
+ rc = -dmu_object_set_blocksize(osd->od_os, dn->dn_object,
+ blksz, 0, oh->ot_tx);
+ LASSERT(ergo(rc == 0, dn->dn_datablksz >= blksz));
+ if (rc < 0)
+ CDEBUG(D_INODE, "object "DFID": change block size"
+ "%u -> %u error rc = %d\n",
+ PFID(lu_object_fid(&obj->oo_dt.do_lu)),
+ dn->dn_datablksz, blksz, rc);
+ }
+ EXIT;
+out_unlock:
+ up_write(&obj->oo_guard);
+out:
+ DB_DNODE_EXIT(db);
+ return rc;
+}
+