On 26/11/2020 10:02, Christoph Hellwig wrote: > On Tue, Nov 24, 2020 at 05:58:13PM +0000, Pavel Begunkov wrote: >> __bio_for_each_bvec(), __bio_for_each_segment() and bio_copy_data_iter() >> fall under conditions of bvec_iter_advance_single(), which is a faster >> and slimmer version of bvec_iter_advance(). Add >> bio_advance_iter_single() and convert them. > > Are you sure about bio_advance_iter()? That API looks like it might Both those listed bio_for_each*() pass bvl.bv_len, which is truncated to current segment by bio_iter_iovec() (i.e. bvec_iter_bvec) or mp_bvec_iter_bvec(). And just to note that I didn't change bio_advance_iter() but added a new function. There is always space for stupid mistakes, but I'm sure. What makes you to think opposite? I may have missed it. > not always be limited to a single segment, and might at least need a > WARN_ON_ONCE to make sure it is not abused. I thought twice about converting other places as you commented before, and it looks saner to not do that exactly for that reason. I prefer to leave *_single() versions for rare but high impact cases like for_each()s. And as it's contained I decided to not add overhead on WARN_ONCE(), e.g. with inlining and w/o string dedup it grows .data section much. -- Pavel Begunkov
