On Sat, Aug 22, 2020 at 07:53:58AM +1000, Dave Chinner wrote: > but iomap only allows BIO_MAX_PAGES when creating the bio. And: > > #define BIO_MAX_PAGES 256 > > So even on a 64k page machine, we should not be building a bio with > more than 16MB of data in it. So how are we getting 4GB of data into > it? BIO_MAX_PAGES is the number of bio_vecs in the bio, it has no direct implication on the size, as each entry can fit up to UINT_MAX bytes.