| Message ID | 20191014144313.26313-1-yangerkun@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iomap: fix the logic about poll io in iomap_dio_bio_actor | expand |
On Mon, Oct 14, 2019 at 10:43:13PM +0800, yangerkun wrote: > Just set REQ_HIPRI for the last bio in iomap_dio_bio_actor. Because > multi bio created by this function can goto different cpu since this > process can be preempted by other process. And in iomap_dio_rw we will > just poll for the last bio. Fix it by only set polled for the last bio. I agree that there is a problem with the separate poll queue now. But doing partially polled I/O also doesn't seem very useful. Until we can find a way to poll for multiple bios from one kiocb I think we need to limit polling to iocbs with just a single bio. Can you look into that? __blkdev_direct_IO do_blockdev_direct_IO probably have the same issues. The former should be just as simple to fix, and for the latter it might make sense to drop polling support entirely.
On 2019/10/15 16:05, Christoph Hellwig wrote: > On Mon, Oct 14, 2019 at 10:43:13PM +0800, yangerkun wrote: >> Just set REQ_HIPRI for the last bio in iomap_dio_bio_actor. Because >> multi bio created by this function can goto different cpu since this >> process can be preempted by other process. And in iomap_dio_rw we will >> just poll for the last bio. Fix it by only set polled for the last bio. > > I agree that there is a problem with the separate poll queue now. But > doing partially polled I/O also doesn't seem very useful. Until we > can find a way to poll for multiple bios from one kiocb I think we need > to limit polling to iocbs with just a single bio. Can you look into > that? __blkdev_direct_IO do_blockdev_direct_IO probably have the same > issues. The former should be just as simple to fix, and for the latter > it might make sense to drop polling support entirely. > Thanks for your suggestion, i will try to fix it. Thanks, Kun. >
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 1fc28c2da279..05dee6e7ca64 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -59,15 +59,16 @@ 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) + struct bio *bio, bool is_poll) { atomic_inc(&dio->ref); - if (dio->iocb->ki_flags & IOCB_HIPRI) + if (is_poll) { bio_set_polled(bio, dio->iocb); - - dio->submit.last_queue = bdev_get_queue(iomap->bdev); - dio->submit.cookie = submit_bio(bio); + dio->submit.last_queue = bdev_get_queue(iomap->bdev); + dio->submit.cookie = submit_bio(bio); + } else + submit_bio(bio); } static ssize_t iomap_dio_complete(struct iomap_dio *dio) @@ -191,7 +192,7 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos, get_page(page); __bio_add_page(bio, page, len, 0); bio_set_op_attrs(bio, REQ_OP_WRITE, flags); - iomap_dio_submit_bio(dio, iomap, bio); + iomap_dio_submit_bio(dio, iomap, bio, false); } static loff_t @@ -255,6 +256,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, do { size_t n; + bool is_poll = false; + if (dio->error) { iov_iter_revert(dio->submit.iter, copied); return 0; @@ -301,7 +304,12 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, copied += n; nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES); - iomap_dio_submit_bio(dio, iomap, bio); + + /* Only set poll for the last bio. */ + if (!nr_pages && dio->iocb->ki_flags & IOCB_HIPRI) + is_poll = true; + + iomap_dio_submit_bio(dio, iomap, bio, is_poll); } while (nr_pages); /*
Just set REQ_HIPRI for the last bio in iomap_dio_bio_actor. Because multi bio created by this function can goto different cpu since this process can be preempted by other process. And in iomap_dio_rw we will just poll for the last bio. Fix it by only set polled for the last bio. Signed-off-by: yangerkun <yangerkun@huawei.com> --- fs/iomap/direct-io.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-)