[OpenWrt-Devel] [RFC PATCH] kernel: drop MIPS: fix cache flushing for highmem pages

Felix Fietkau nbd at nbd.name
Wed Dec 19 04:57:21 EST 2018

On 2018-12-18 17:43, Rosen Penev wrote:
> On Tue, Dec 18, 2018 at 2:35 AM Kevin 'ldir' Darbyshire-Bryant
> <ldir at darbyshire-bryant.me.uk> wrote:
>> Signed-off-by: Kevin Darbyshire-Bryant <ldir at darbyshire-bryant.me.uk>
>> ---
>> This patch, in a variety of forms, has been around since beginning 2016
>> as e756c2bb07, ending up in present form 0aa6c7df60 (kernel 4.4.13 bump)
>> and carried forward ever since.
>> There have been a number of MIPS kernel memory handling changes since,
>> including VDSO fixes that meant openwrt patches have been dropped with
>> no apparent fallout.
>> I'm basically wondering if this patch needs to still exist in the kernel
>> 4.14.88 world?  I have been running without this patch for 3+ months on
>> Archer C7 v2 with no obvious ill effects (I'd expect to see "nasty
>> segfaults and kernel crashes")
>> If it does still need to exist, should it go upstream?
>> Thoughts, comments, more testers?
> I've tested removing the patch on a 512MB mt7621 device where HIGHMEM
> is used for the second 256MB. No issues.
I think to be on the safe side we should test running fuse (ntfs-3g or
sshfs or something similar) on such a device. If that doesn't turn up
any weird hangs or data corruption within a few minutes of use, I'm all
for dropping this patch.


- Felix

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