Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [RESEND PATCH] fs/aio: Replace kmap{,_atomic}() with kmap_local_page() | Date | Wed, 19 Oct 2022 11:41:21 -0400 |
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"Fabio M. De Francesco" <fmdefrancesco@gmail.com> 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@redhat.com>
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