On Fri, Nov 20, 2020 at 06:06:54PM +0800, JeffleXu wrote: > > On 11/20/20 1:55 AM, Christoph Hellwig wrote: > > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > > > index 933f234d5bec..396ac0f91a43 100644 > > > --- a/fs/iomap/direct-io.c > > > +++ b/fs/iomap/direct-io.c > > > @@ -309,6 +309,16 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > > > copied += n; > > > nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); > > > + /* > > > + * The current dio needs to be split into multiple bios here. > > > + * iopoll for split bio will cause subtle trouble such as > > > + * hang when doing sync polling, while iopoll is initially > > > + * for small size, latency sensitive IO. Thus disable iopoll > > > + * if split needed. > > > + */ > > > + if (nr_pages) > > > + dio->iocb->ki_flags &= ~IOCB_HIPRI; > > I think this is confusing two things. > > Indeed there's two level of split concerning this issue when doing sync > iopoll. > > > The first is that one bio got split in block-core, and patch 1 of this patch > set just fixes this. > > > Second is that one dio got split into multiple bios in fs layer, and patch 2 > fixes this. > > > > One is that we don't handle > > polling well when there are multiple bios. For this I think we should > > only call bio_set_polled when we know there is a single bio. > > > How about the following patch: > > > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -60,12 +60,12 @@ int iomap_dio_iopoll(struct kiocb *kiocb, bool spin) > ??EXPORT_SYMBOL_GPL(iomap_dio_iopoll); > > ??static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap > *iomap, > -???????????????????????????? struct bio *bio, loff_t pos) > +???????????????????????????? struct bio *bio, loff_t pos, bool split) This seems pretty messed up by your mailer and I have a hard time reading it. Can you resend it?
