On Fri, Aug 14, 2020 at 10:26:23AM +0800, Zhaoyang Huang wrote: > On Fri, Aug 14, 2020 at 10:20 AM Zhaoyang Huang <huangzhaoyang@xxxxxxxxx> wrote: > > > > On Fri, Aug 14, 2020 at 10:07 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > > > 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. > > No, What I want to fix is the file within one process's context keeps > > using the initialized value when it is opened and not sync with new > > value when bdi->ra_pages changes. > So you mean it is just the desired behavior as having the opened file > use the initialized value even if bdi->ra_pages changed via sysfs? That's right. If that's not the behaviour you want, call fadvise(POSIX_FADV_NORMAL). > > > > > > You haven't said what problem you're facing, so I really can't be more > > > helpful.
