On Mon, Mar 23, 2020 at 08:10:54AM -0700, Matthew Wilcox wrote: > > That looks silly to me. This just means we'll keep iterating over > > small bios for readahead.. Either we just ignore the different gfp > > mask, or we need to go all the way and handle errors, although that > > doesn't really look nice. > > I'm not sure it's silly, Oh well, I'm not going to be in the way of fixing a bug I added. So feel free to go ahead with this and mention it matches mpage_readpages. > although I'd love to see bio_alloc() support > nr_iovecs == 0 meaning "allocate me any size biovec and tell me what > size I got in ->bi_max_vecs". By allocating a small biovec this time, > we do one allocation rather than two, and maybe by the time we come to > allocate the next readahead bio, kswapd will have succeeded in freeing > up more memory for us. Sounds easy enough - especially as callers don't need to look at bi_max_vecs anyway, that is the job of bio_add_page and friends. That being said an upper bound still sounds useful - no need to allocate a a gigantic bio if we know we only need a few pages.
