On Wed, Oct 21, 2020 at 5:04 AM Sergei Shtepa <sergei.shtepa@xxxxxxxxx> wrote: > > Hello everyone! Requesting for your comments and suggestions. > > # blk-filter > > Block layer filter allows to intercept BIO requests to a block device. > > Interception is performed at the very beginning of the BIO request > processing, and therefore does not affect the operation of the request > processing queue. This also makes it possible to intercept requests from > a specific block device, rather than from the entire disk. > > The logic of the submit_bio function has been changed - since the > function execution results are not processed anywhere (except for swap > and direct-io) the function won't return a value anymore. Your desire to switch to a void return comes exactly when I've noticed we need it. ->submit_bio's blk_qc_t return is the cookie assigned by blk-mq. Up to this point we haven't actually used it for bio-based devices but it seems clear we'll soon need for bio-based IO polling support. Just today, I've been auditing drivers/md/dm.c with an eye toward properly handling the blk_qc_t return (or lack thereof) from various DM methods. It could easily be that __submit_bio_noacct and __submit_bio_noacct_mq will be updated to do something meaningful with the returned cookie (or that DM will) to facilitate proper IO polling. Mike
