On Thu, May 23, 2024 at 01:08:02PM -0700, Andrew Morton wrote: > On Mon, 13 May 2024 21:23:39 +0800 Liu Wei <liuwei09@xxxxxxxx> wrote: > > > After commit (6be96d3ad3 fs: return if direct I/O will trigger writeback), > > when we issuing AIO with direct I/O and IOCB_NOWAIT on a block device, the > > process context will not be blocked. > > > > However, if the device already has page cache in memory, EAGAIN will be > > returned. And even when trying to reissue the AIO with direct I/O and > > IOCB_NOWAIT again, we consistently receive EAGAIN. > > > > Maybe a better way to deal with it: filemap_fdatawrite_range dirty pages > > with WB_SYNC_NONE flag, and invalidate_mapping_pages unmapped pages at > > the same time. > > Can't userspace do this? If EAGAIN, sync the fd and retry the IO? I don't think that it can, because the pages will still be there, even if now clean? I think the idea was to punt to a worker thread which could sleep and retry without NOWAIT. But let's see what someone involved in this patch has to say about the intent.
