From: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp> This decrements a reference count of the old data object when allocating a new data object on CoW. Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp> --- sheep/gateway.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 102 insertions(+), 1 deletion(-) diff --git a/sheep/gateway.c b/sheep/gateway.c index 506cea5..fb7ed21 100644 --- a/sheep/gateway.c +++ b/sheep/gateway.c @@ -317,9 +317,88 @@ static int gateway_forward_request(struct request *req) return err_ret; } +static int prepare_obj_refcnt(const struct sd_req *hdr, uint32_t *vids, + struct generation_reference *refs) +{ + int ret; + size_t nr_vids = hdr->data_length / sizeof(*vids); + uint64_t offset; + int start; + + offset = hdr->obj.offset - offsetof(struct sd_inode, data_vdi_id); + start = offset / sizeof(*vids); + + ret = read_object(hdr->obj.oid, (char *)vids, nr_vids * sizeof(vids[0]), + offsetof(struct sd_inode, data_vdi_id[start])); + if (ret != SD_RES_SUCCESS) { + sd_eprintf("failed to read vdi, %" PRIx64, hdr->obj.oid); + return ret; + } + ret = read_object(hdr->obj.oid, (char *)refs, nr_vids * sizeof(refs[0]), + offsetof(struct sd_inode, data_ref[start])); + if (ret != SD_RES_SUCCESS) { + sd_eprintf("failed to read vdi, %" PRIx64, hdr->obj.oid); + return ret; + } + + return ret; +} + +/* + * This function decreases a refcnt of vid_to_data_oid(old_vid, idx) and + * increases one of vid_to_data_oid(new_vid, idx) + */ +static int update_obj_refcnt(const struct sd_req *hdr, uint32_t *vids, + uint32_t *new_vids, + struct generation_reference *refs) +{ + int i, start, ret = SD_RES_SUCCESS; + size_t nr_vids = hdr->data_length / sizeof(*vids); + uint64_t offset; + + offset = hdr->obj.offset - offsetof(struct sd_inode, data_vdi_id); + start = offset / sizeof(*vids); + + for (i = 0; i < nr_vids; i++) { + if (vids[i] == 0 || vids[i] == new_vids[i]) + continue; + + ret = dec_object_refcnt(vid_to_data_oid(vids[i], i + start), + refs[i].generation, refs[i].count); + if (ret != SD_RES_SUCCESS) + sd_eprintf("fail, %d", ret); + + refs[i].generation = 0; + refs[i].count = 0; + } + + return write_object(hdr->obj.oid, (char *)refs, nr_vids * sizeof(*refs), + offsetof(struct sd_inode, + data_ref) + start * sizeof(*refs), + false); +} + +/* + * return true if the request updates a data_vdi_id field of a vdi object + * + * XXX: we assume that VMs don't update the inode header and the data_vdi_id + * field at the same time. + */ +static bool is_data_vid_update(const struct sd_req *hdr) +{ + return is_vdi_obj(hdr->obj.oid) && + SD_INODE_HEADER_SIZE <= hdr->obj.offset && + hdr->obj.offset + hdr->data_length <= + offsetof(struct sd_inode, data_ref); +} + int gateway_write_obj(struct request *req) { uint64_t oid = req->rq.obj.oid; + int ret; + struct sd_req *hdr = &req->rq; + uint32_t *vids = NULL, *new_vids = req->data; + struct generation_reference *refs = NULL; if (oid_is_readonly(oid)) return SD_RES_READONLY; @@ -327,7 +406,29 @@ int gateway_write_obj(struct request *req) if (!bypass_object_cache(req)) return object_cache_handle_request(req); - return gateway_forward_request(req); + if (is_data_vid_update(hdr)) { + size_t nr_vids = hdr->data_length / sizeof(*vids); + + /* read the previous vids to discard their references later */ + vids = xzalloc(sizeof(*vids) * nr_vids); + refs = xzalloc(sizeof(*refs) * nr_vids); + ret = prepare_obj_refcnt(hdr, vids, refs); + if (ret != SD_RES_SUCCESS) + goto out; + } + + ret = gateway_forward_request(req); + if (ret != SD_RES_SUCCESS) + goto out; + + if (is_data_vid_update(hdr)) { + sd_dprintf("udpate reference counts, %" PRIx64, hdr->obj.oid); + ret = update_obj_refcnt(hdr, vids, new_vids, refs); + } +out: + free(vids); + free(refs); + return ret; } int gateway_create_and_write_obj(struct request *req) -- 1.7.9.5 |