From: Balbir Singh <bsingharora@gmail.com>
To: David Hildenbrand <david@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-acpi@vger.kernel.org, xen-devel@lists.xenproject.org,
devel@linuxdriverproject.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Rashmica Gupta <rashmica.g@gmail.com>,
Michael Neuling <mikey@neuling.org>
Subject: Re: [PATCH v2 5/6] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages()
Date: Tue, 25 Sep 2018 22:15:04 +1000 [thread overview]
Message-ID: <20180925121504.GH8537@350D> (raw)
In-Reply-To: <20180925091457.28651-6-david@redhat.com>
On Tue, Sep 25, 2018 at 11:14:56AM +0200, David Hildenbrand wrote:
> Let's perform all checking + offlining + removing under
> device_hotplug_lock, so nobody can mess with these devices via
> sysfs concurrently.
>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Rashmica Gupta <rashmica.g@gmail.com>
> Cc: Balbir Singh <bsingharora@gmail.com>
> Cc: Michael Neuling <mikey@neuling.org>
> Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
> Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> arch/powerpc/platforms/powernv/memtrace.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index fdd48f1a39f7..d84d09c56af9 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg)
> return 0;
> }
>
> +/* called with device_hotplug_lock held */
> static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
> {
> u64 end_pfn = start_pfn + nr_pages - 1;
> @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
> end_pfn = round_down(end_pfn - nr_pages, nr_pages);
>
> for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
> + lock_device_hotplug();
Why not grab the lock before the for loop? That way we can avoid bad cases like a
large node being scanned for a small number of pages (nr_pages). Ideally we need
a cond_resched() in the loop, but I guess offline_pages() has one.
Acked-by: Balbir Singh <bsingharora@gmail.com>
next prev parent reply other threads:[~2018-09-25 12:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-25 9:14 [PATCH v2 0/6] mm: online/offline_pages called w.o. mem_hotplug_lock David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 1/6] mm/memory_hotplug: make remove_memory() take the device_hotplug_lock David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 2/6] mm/memory_hotplug: make add_memory() " David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 3/6] mm/memory_hotplug: fix online/offline_pages called w.o. mem_hotplug_lock David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 4/6] powerpc/powernv: hold device_hotplug_lock when calling device_online() David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 5/6] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages() David Hildenbrand
2018-09-25 12:15 ` Balbir Singh [this message]
2018-09-26 10:09 ` David Hildenbrand
2018-09-25 9:14 ` [PATCH v2 6/6] memory-hotplug.txt: Add some details about locking internals David Hildenbrand
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