[0/2] Don't allow REQ_NOWAIT for bio splitting

Message

Jens Axboe Jan. 4, 2023, 4:09 p.m. UTC

Hi,

If we end up needing to split a bio that is marked with REQ_NOWAIT, it's
entirely possible that any part of the split bio will hit a failure
trying to get submitted. If this happens, then the entire request ends
up being errored with BLK_STS_AGAIN, even if any parts of this bio has
been read or written to the device/file.

Rather than end up in this odd state, disallow splitting with REQ_NOWAIT.
If we end the entire request upfront with EAGAIN, then we don't end up
with a partially written IO that still returns EAGAIN.