On Wed, Oct 12, 2022 at 11:13:56AM +0200, Fabio M. De Francesco wrote: > The use of kmap() is 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/cramfs is safe everywhere, it should be preferred. > > Therefore, replace kmap() with kmap_local_page() in fs/cramfs. Instead > of open-coding kmap_local_page() + memcpy(), use memcpy_from_page(). > > Cc: "Venkataramanan, Anirudh" <anirudh.venkataramanan@xxxxxxxxx> > Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> > --- Looks good to me, Reviewed-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
