From 03a07c92a9ed9938d828ca7f1d11b8bc63a7bb89 Mon Sep 17 00:00:00 2001 From: Goldwyn Rodrigues Date: Tue, 20 Jun 2017 07:05:46 -0500 Subject: block: return on congested block device A new bio operation flag REQ_NOWAIT is introduced to identify bio's orignating from iocb with IOCB_NOWAIT. This flag indicates to return immediately if a request cannot be made instead of retrying. Stacked devices such as md (the ones with make_request_fn hooks) currently are not supported because it may block for housekeeping. For example, an md can have a part of the device suspended. For this reason, only request based devices are supported. In the future, this feature will be expanded to stacked devices by teaching them how to handle the REQ_NOWAIT flags. Reviewed-by: Christoph Hellwig Reviewed-by: Jens Axboe Signed-off-by: Goldwyn Rodrigues Signed-off-by: Jens Axboe --- fs/direct-io.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'fs/direct-io.c') diff --git a/fs/direct-io.c b/fs/direct-io.c index e8baaabebf13..c87077d1dc33 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -479,8 +479,12 @@ static blk_status_t dio_bio_complete(struct dio *dio, struct bio *bio) unsigned i; blk_status_t err = bio->bi_status; - if (err) - dio->io_error = -EIO; + if (err) { + if (err == BLK_STS_AGAIN && (bio->bi_opf & REQ_NOWAIT)) + dio->io_error = -EAGAIN; + else + dio->io_error = -EIO; + } if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) { bio_check_pages_dirty(bio); /* transfers ownership */ @@ -1194,6 +1198,8 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, if (iov_iter_rw(iter) == WRITE) { dio->op = REQ_OP_WRITE; dio->op_flags = REQ_SYNC | REQ_IDLE; + if (iocb->ki_flags & IOCB_NOWAIT) + dio->op_flags |= REQ_NOWAIT; } else { dio->op = REQ_OP_READ; } -- cgit v1.2.3-55-g7522