"Fabio M. De Francesco" <fmdefrancesco@xxxxxxxxx> writes: > The use of kmap() and kmap_atomic() are being deprecated in favor of > kmap_local_page(). > > There are two main problems with kmap(): (1) It comes with an overhead as > the mapping space is restricted and protected by a global lock for > synchronization and (2) it also requires global TLB invalidation when the > kmap’s pool wraps and it might block when the mapping space is fully > utilized until a slot becomes available. > > With kmap_local_page() the mappings are per thread, CPU local, can take > page faults, and can be called from any context (including interrupts). > It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, > the tasks can be preempted and, when they are scheduled to run again, the > kernel virtual addresses are restored and still valid. > > Since its use in fs/aio.c is safe everywhere, it should be preferred. That sentence is very ambiguous. I don't know what "its" refers to, and I'm not sure what "safe" means in this context. The patch looks okay to me. Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
