On 6/11/25 10:00 AM, Keith Busch wrote: > On Wed, Jun 11, 2025 at 09:46:31AM +0900, Damien Le Moal wrote: >> On 6/11/25 8:18 AM, Keith Busch wrote: >>> >>> I think you could just prep the encryption at the point the bio is split >>> to its queue's limits, and then all you need to do after that is ensure >>> the limits don't exceed what the fallback requires (which appears to >>> just be a simple segment limitation). It looks like most of the bio >>> based drivers split to limits already. >> >> Nope, at least not DM, and by that, I mean not in the sense of splitting BIOs >> using bio_split_to_limits(). The only BIOs being split are "abnormal" ones, >> such as discard. >> >> That said, DM does split the BIOs through cloning and also has the "accept >> partial" thing, which is used in many places and allows DM target drivers to >> split BIOs as they are received, but not necessarilly based on the device queue >> limits (e.g. dm-crypt splits reads and writes using an internal >> max_read|write_size limit). >> >> So inline crypto on top of a DM/bio-based device may need some explicit >> splitting added in dm.c (__max_io_len() maybe ?). > > Ah, thanks for pointing that out! In that case, could we have dm > consider the bio "abnormal" when bio_has_crypt_ctx(bio) is true? That > way it does the split-to-limits for these, and dm appears to do that > action very early before its own split/clone actions on the resulting > bio. That sounds reasonable to me. -- Damien Le Moal Western Digital Research
