Re: [PATCHv4 18/43] block: define BIO_MAX_PAGES to HPAGE_PMD_NR if huge page cache enabled

[Christoph Hellwig]

On Tue, Oct 25, 2016 at 03:13:17AM +0300, Kirill A. Shutemov wrote:
> We are going to do IO a huge page a time. So we need BIO_MAX_PAGES to be
> at least HPAGE_PMD_NR. For x86-64, it's 512 pages.

NAK.  The maximum bio size should not depend on an obscure vm config,
please send a standalone patch increasing the size to the block list,
with a much long explanation.  Also you can't simply increase the size
of the largers pool, we'll probably need more pools instead, or maybe
even implement a similar chaining scheme as we do for struct
scatterlist.