Re: [PATCH] patches: add patch for compat/lib-rhashtable.c

[Johannes Berg <johannes@sipsolutions.net>]

On Fri, 2017-05-19 at 21:46 +0100, Arend van Spriel wrote:
> The file compat/lib-rhashtable.c is a copy from the backported kernel
> source lib/rhashtable.c. This patch reverts a recent change to that
> file, ie. commit 43ca5bc4f72e ("lib/rhashtable.c: simplify a strange
> allocation pattern"). It introduced the function
> gfpflags_allow_blocking()
> introduced in 4.4 kernel and kvmalloc() introduced in 4.12-rc1.
> Looking
> at those functions backporting them is complicated so instead add
> this
> patch that reverts the change for kernel prior to 4.12.

Thanks Arend!

Why do you think backporting it is complicated though?

kvmalloc() is just kvmalloc_node(), and if we disregard the
__vmalloc_node_flags_caller() but - since kvmalloc() doesn't care about
node anyway - just use __vmalloc() there, it should be easy? The
pgprot_t argument is just PAGE_KERNEL, and the other stuff doesn't
really matter.

gfpflags_allow_blocking() is a pretty simple inline, and even if we'd
implement it to always return false we'd get the old rhashtable
behaviour.

johannes
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