On 10/12/20 9:19 AM, Eric Biggers wrote: > On Sun, Oct 11, 2020 at 11:56:35PM -0700, Ira Weiny wrote: >>> And I still don't really understand. After this patchset, there is still code >>> nearly identical to the above (doing a temporary mapping just for a memcpy) that >>> would still be using kmap_atomic(). >> I don't understand. You mean there would be other call sites calling: >> >> kmap_atomic() >> memcpy() >> kunmap_atomic() > Yes, there are tons of places that do this. Try 'git grep -A6 kmap_atomic' > and look for memcpy(). > > Hence why I'm asking what will be the "recommended" way to do this... > kunmap_thread() or kmap_atomic()? kmap_atomic() is always preferred over kmap()/kmap_thread(). kmap_atomic() is _much_ more lightweight since its TLB invalidation is always CPU-local and never broadcast. So, basically, unless you *must* sleep while the mapping is in place, kmap_atomic() is preferred.
