From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH v2 5/6] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages() Date: Wed, 26 Sep 2018 12:09:10 +0200 Message-ID: <19de0a52-2abd-6e79-1b8e-dcf17eff3fba@redhat.com> References: <20180925091457.28651-1-david@redhat.com> <20180925091457.28651-6-david@redhat.com> <20180925121504.GH8537@350D> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180925121504.GH8537@350D> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Balbir Singh 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 , Paul Mackerras , Michael Ellerman , Rashmica Gupta , Michael Neuling List-Id: linux-acpi@vger.kernel.org On 25/09/2018 14:15, Balbir Singh wrote: > 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 >> Cc: Paul Mackerras >> Cc: Michael Ellerman >> Cc: Rashmica Gupta >> Cc: Balbir Singh >> Cc: Michael Neuling >> Reviewed-by: Pavel Tatashin >> Reviewed-by: Rashmica Gupta >> Signed-off-by: David Hildenbrand >> --- >> 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. Yes, it does. I can move it out of the loop, thanks! > > Acked-by: Balbir Singh > -- Thanks, David / dhildenb