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Wysocki" , "mike.travis@hpe.com" , Ingo Molnar , Andrew Banman , Oscar Salvador , Michal Hocko , Pavel Tatashin , Qian Cai , Wei Yang , Arun KS , Mathieu Malaterre Subject: Re: [PATCH v2 4/8] mm/memory_hotplug: Create memory block devices after arch_add_memory() Message-ID: <20190509143151.zexjmwu3ikkmye7i@master> Reply-To: Wei Yang References: <20190507183804.5512-1-david@redhat.com> <20190507183804.5512-5-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190507183804.5512-5-david@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 07, 2019 at 08:38:00PM +0200, David Hildenbrand wrote: >Only memory to be added to the buddy and to be onlined/offlined by >user space using memory block devices needs (and should have!) memory >block devices. > >Factor out creation of memory block devices Create all devices after >arch_add_memory() succeeded. We can later drop the want_memblock parameter, >because it is now effectively stale. > >Only after memory block devices have been added, memory can be onlined >by user space. This implies, that memory is not visible to user space at >all before arch_add_memory() succeeded. > >Cc: Greg Kroah-Hartman >Cc: "Rafael J. Wysocki" >Cc: David Hildenbrand >Cc: "mike.travis@hpe.com" >Cc: Andrew Morton >Cc: Ingo Molnar >Cc: Andrew Banman >Cc: Oscar Salvador >Cc: Michal Hocko >Cc: Pavel Tatashin >Cc: Qian Cai >Cc: Wei Yang >Cc: Arun KS >Cc: Mathieu Malaterre >Signed-off-by: David Hildenbrand >--- > drivers/base/memory.c | 70 ++++++++++++++++++++++++++---------------- > include/linux/memory.h | 2 +- > mm/memory_hotplug.c | 15 ++++----- > 3 files changed, 53 insertions(+), 34 deletions(-) > >diff --git a/drivers/base/memory.c b/drivers/base/memory.c >index 6e0cb4fda179..862c202a18ca 100644 >--- a/drivers/base/memory.c >+++ b/drivers/base/memory.c >@@ -701,44 +701,62 @@ static int add_memory_block(int base_section_nr) > return 0; > } > >+static void unregister_memory(struct memory_block *memory) >+{ >+ BUG_ON(memory->dev.bus != &memory_subsys); >+ >+ /* drop the ref. we got via find_memory_block() */ >+ put_device(&memory->dev); >+ device_unregister(&memory->dev); >+} >+ > /* >- * need an interface for the VM to add new memory regions, >- * but without onlining it. >+ * Create memory block devices for the given memory area. Start and size >+ * have to be aligned to memory block granularity. Memory block devices >+ * will be initialized as offline. > */ >-int hotplug_memory_register(int nid, struct mem_section *section) >+int hotplug_memory_register(unsigned long start, unsigned long size) One trivial suggestion about the function name. For memory_block device, sometimes we use the full name find_memory_block init_memory_block add_memory_block But sometimes we use *nick* name hotplug_memory_register register_memory unregister_memory This is a little bit confusion. Can we use one name convention here? [...] > /* >@@ -1106,6 +1100,13 @@ int __ref add_memory_resource(int nid, struct resource *res) > if (ret < 0) > goto error; > >+ /* create memory block devices after memory was added */ >+ ret = hotplug_memory_register(start, size); >+ if (ret) { >+ arch_remove_memory(nid, start, size, NULL); Functionally, it works I think. But arch_remove_memory() would remove pages from zone. At this point, we just allocate section/mmap for pages, the zones are empty and pages are not connected to zone. Function zone = page_zone(page); always gets zone #0, since pages->flags is 0 at this point. This is not exact. Would we add some comment to mention this? Or we need to clean up arch_remove_memory() to take out __remove_zone()? >+ goto error; >+ } >+ > if (new_node) { > /* If sysfs file of new node can't be created, cpu on the node > * can't be hot-added. There is no rollback way now. >-- >2.20.1 -- Wei Yang Help you, Help me