linux-kernel - Re: [PATCH stable 5.10 1/1] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block

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Date:   Mon, 19 Jun 2023 08:20:43 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     mawupeng <mawupeng1@...wei.com>
Cc:     akpm@...ux-foundation.org, david@...hat.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        richard.weiyang@...ux.alibaba.com, mst@...hat.com,
        jasowang@...hat.com, pankaj.gupta.linux@...il.com,
        mhocko@...nel.org, osalvador@...e.de
Subject: Re: [PATCH stable 5.10 1/1] mm/memory_hotplug: extend
 offline_and_remove_memory() to handle more than one memory block

On Wed, Jun 14, 2023 at 02:45:58PM +0800, mawupeng wrote:
> 
> 
> On 2023/6/14 14:35, Greg KH wrote:
> > On Wed, Jun 14, 2023 at 02:19:00PM +0800, Wupeng Ma wrote:
> >> From: David Hildenbrand <david@...hat.com>
> >>
> >> virtio-mem soon wants to use offline_and_remove_memory() memory that
> >> exceeds a single Linux memory block (memory_block_size_bytes()). Let's
> >> remove that restriction.
> >>
> >> Let's remember the old state and try to restore that if anything goes
> >> wrong. While re-onlining can, in general, fail, it's highly unlikely to
> >> happen (usually only when a notifier fails to allocate memory, and these
> >> are rather rare).
> >>
> >> This will be used by virtio-mem to offline+remove memory ranges that are
> >> bigger than a single memory block - for example, with a device block
> >> size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory
> >> block size of 128MB.
> >>
> >> While we could compress the state into 2 bit, using 8 bit is much
> >> easier.
> >>
> >> This handling is similar, but different to acpi_scan_try_to_offline():
> >>
> >> a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG
> >> optimization is still relevant - it should only apply to ZONE_NORMAL
> >> (where we have no guarantees). If relevant, we can always add it.
> >>
> >> b) acpi_scan_try_to_offline() simply onlines all memory in case
> >> something goes wrong. It doesn't restore previous online type. Let's do
> >> that, so we won't overwrite what e.g., user space configured.
> >>
> >> Reviewed-by: Wei Yang <richard.weiyang@...ux.alibaba.com>
> >> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> >> Cc: Jason Wang <jasowang@...hat.com>
> >> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
> >> Cc: Michal Hocko <mhocko@...nel.org>
> >> Cc: Oscar Salvador <osalvador@...e.de>
> >> Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
> >> Cc: Andrew Morton <akpm@...ux-foundation.org>
> >> Signed-off-by: David Hildenbrand <david@...hat.com>
> >> Link: https://lore.kernel.org/r/20201112133815.13332-28-david@redhat.com
> >> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> >> Acked-by: Andrew Morton <akpm@...ux-foundation.org>
> >> ---
> >>  mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++-------
> >>  1 file changed, 89 insertions(+), 16 deletions(-)
> > 
> > As you forwarded this patch on, you too need to sign-off on it.
> 
> Thanks for reminding me.
> 
> Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>
> 
> > 
> > Also, what is the git id of the commit in Linus's tree?
> 
> Sorry, here is the commit in Linus's tree.
> 
> commit 8dc4bb58a146655eb057247d7c9d19e73928715b upstream.

Please resend the change with both of these things fixed up, so I don't
have to manually do it :)

thanks,

greg k-h