On Fri, 2020-09-11 at 10:47 +0100, Christoph Hellwig wrote: > > Hi Andrew > > Sorry, I am still not quite understanding your above three > > questions. > > > > Based on my shallow understanding, ra_pages is associated with > > read_ahead_kb. Seems ra_pages controls the maximum read-ahead > > window > > size, but it doesn't work when the requested size exceeds > > ra_pages. > > > > If I set the read_ahead_kb to 0, also, as Christoph mentioned, MTD > > forcibly sets ra_pages to 0. I think the intention is that only > > wants > > to disable read-ahead, however, doesn't want > > generic_file_buffered_read() to split the request and read data > > with > > 4KB chunk size separately. > > They way I understood Richard this is intentional. Hi Christoph Thanks. understood now, MTD expects this result. Even so, I think this patch doesn't impact MTD because the flash-based FS only achieved the readpage. Inside __do_page_cache_readahead will use mapping->a_ops- >readpage to read data. Thanks, Bean
