1081a1082,1157
>
> int
> zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
> uint64_t *towrite, uint64_t *tooverwrite)
> {
> zap_t *zap;
> int err = 0;
>
>
> /*
> * Since, we don't have a name, we cannot figure out which blocks will
> * be affected in this operation. So, account for the worst case :
> * - 3 blocks overwritten: target leaf, ptrtbl block, header block
> * - 4 new blocks written if adding:
> * - 2 blocks for possibly split leaves,
> * - 2 grown ptrtbl blocks
> *
> * This also accomodates the case where an add operation to a fairly
> * large microzap results in a promotion to fatzap.
> */
> if (name == NULL) {
> *towrite += (3 + (add ? 4 : 0)) * SPA_MAXBLOCKSIZE;
> return (err);
> }
>
> /*
> * We lock the zap with adding == FALSE. Because, if we pass
> * the actual value of add, it could trigger a mzap_upgrade().
> * At present we are just evaluating the possibility of this operation
> * and hence we donot want to trigger an upgrade.
> */
> err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
> if (err)
> return (err);
>
> if (!zap->zap_ismicro) {
> zap_name_t *zn = zap_name_alloc(zap, name, MT_EXACT);
> if (zn) {
> err = fzap_count_write(zn, add, towrite,
> tooverwrite);
> zap_name_free(zn);
> } else {
> /*
> * We treat this case as similar to (name == NULL)
> */
> *towrite += (3 + (add ? 4 : 0)) * SPA_MAXBLOCKSIZE;
> }
> } else {
> /*
> * We are here if (name != NULL) and this is a micro-zap.
> * We account for the header block depending on whether it
> * is freeable.
> *
> * Incase of an add-operation it is hard to find out
> * if this add will promote this microzap to fatzap.
> * Hence, we consider the worst case and account for the
> * blocks assuming this microzap would be promoted to a
> * fatzap.
> *
> * 1 block overwritten : header block
> * 4 new blocks written : 2 new split leaf, 2 grown
> * ptrtbl blocks
> */
> if (dmu_buf_freeable(zap->zap_dbuf))
> *tooverwrite += SPA_MAXBLOCKSIZE;
> else
> *towrite += SPA_MAXBLOCKSIZE;
>
> if (add) {
> *towrite += 4 * SPA_MAXBLOCKSIZE;
> }
> }
>
> zap_unlockdir(zap);
> return (err);
> }