On 26/11/2020 12:32, Pavel Begunkov wrote: > 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. Christoph, any doubts left? >> 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
