On Fri, Aug 14, 2020 at 02:43:55AM +0100, Matthew Wilcox wrote: > On Fri, Aug 14, 2020 at 09:30:11AM +0800, Zhaoyang Huang wrote: > > file->f_ra->ra_pages will remain the initialized value since it opend, which may > > be NOT equal to bdi->ra_pages as the latter one is updated somehow(etc, > > echo xxx > /sys/block/dm/queue/read_ahead_kb).So sync ra->ra_pages to the > > updated value when sync read. > > It still ignores the work done by shrink_readahead_size_eio() > and fadvise(POSIX_FADV_SEQUENTIAL). ... by the way, if you're trying to update one particular file's readahead state, you can just call fadvise(POSIX_FADV_NORMAL) on it. If you want to update every open file's ra_pages by writing to sysfs, then just no. We don't do that. You haven't said what problem you're facing, so I really can't be more helpful.
