On lunedì 25 luglio 2022 19:17:13 CEST Viacheslav Dubeyko wrote: > > > On Jul 24, 2022, at 1:50 PM, Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> wrote: > > > > kmap() is being deprecated in favor of kmap_local_page(). > > > > There are two main problems with kmap(): (1) It comes with an overhead as > > 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 are still valid. > > > > Since its use in bitmap.c is safe everywhere, it should be preferred. > > > > Therefore, replace kmap() with kmap_local_page() in bnode.c. > > > > Looks good. Maybe, it makes sense to combine all kmap() related modifications in HFS+ into > one patchset? > > Reviewed by: Viacheslav Dubeyko <slava@xxxxxxxxxxx> Thanks for your reviews of this and of the other patch to bnode.c. Actually, I started with the first file I met (bnode.c) because I noticed that maintainers don't need to care about any special ordering for applying the patches, since each of them is self-contained. This is why I haven't thought of making a series of them. Currently only one file is still left with some kmap() call sites. I'll work on that within the next days. Again thanks, Fabio > Thanks, > Slava. > > > Suggested-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx> > > --- > > fs/hfsplus/bitmap.c | 18 +++++++++--------- > > 1 file changed, 9 insertions(+), 9 deletions(-) [snip]
