From: David Hildenbrand david@redhat.com
[ Upstream commit 381eab4a6ee81266f8dddc62e57376c7e584e5b8 ]
There seem to be some problems as result of 30467e0b3be ("mm, hotplug: fix concurrent memory hot-add deadlock"), which tried to fix a possible lock inversion reported and discussed in [1] due to the two locks a) device_lock() b) mem_hotplug_lock
While add_memory() first takes b), followed by a) during bus_probe_device(), onlining of memory from user space first took a), followed by b), exposing a possible deadlock.
In [1], and it was decided to not make use of device_hotplug_lock, but rather to enforce a locking order.
The problems I spotted related to this:
1. Memory block device attributes: While .state first calls mem_hotplug_begin() and the calls device_online() - which takes device_lock() - .online does no longer call mem_hotplug_begin(), so effectively calls online_pages() without mem_hotplug_lock.
2. device_online() should be called under device_hotplug_lock, however onlining memory during add_memory() does not take care of that.
In addition, I think there is also something wrong about the locking in
3. arch/powerpc/platforms/powernv/memtrace.c calls offline_pages() without locks. This was introduced after 30467e0b3be. And skimming over the code, I assume it could need some more care in regards to locking (e.g. device_online() called without device_hotplug_lock. This will be addressed in the following patches.
Now that we hold the device_hotplug_lock when - adding memory (e.g. via add_memory()/add_memory_resource()) - removing memory (e.g. via remove_memory()) - device_online()/device_offline()
We can move mem_hotplug_lock usage back into online_pages()/offline_pages().
Why is mem_hotplug_lock still needed? Essentially to make get_online_mems()/put_online_mems() be very fast (relying on device_hotplug_lock would be very slow), and to serialize against addition of memory that does not create memory block devices (hmm).
[1] http://driverdev.linuxdriverproject.org/pipermail/ driverdev-devel/ 2015-February/065324.html
This patch is partly based on a patch by Vitaly Kuznetsov.
Link: http://lkml.kernel.org/r/20180925091457.28651-4-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Pavel Tatashin pavel.tatashin@microsoft.com Reviewed-by: Rashmica Gupta rashmica.g@gmail.com Reviewed-by: Oscar Salvador osalvador@suse.de Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Paul Mackerras paulus@samba.org Cc: Michael Ellerman mpe@ellerman.id.au Cc: "Rafael J. Wysocki" rjw@rjwysocki.net Cc: Len Brown lenb@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: "K. Y. Srinivasan" kys@microsoft.com Cc: Haiyang Zhang haiyangz@microsoft.com Cc: Stephen Hemminger sthemmin@microsoft.com Cc: Martin Schwidefsky schwidefsky@de.ibm.com Cc: Heiko Carstens heiko.carstens@de.ibm.com Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Juergen Gross jgross@suse.com Cc: Rashmica Gupta rashmica.g@gmail.com Cc: Michael Neuling mikey@neuling.org Cc: Balbir Singh bsingharora@gmail.com Cc: Kate Stewart kstewart@linuxfoundation.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Philippe Ombredanne pombredanne@nexb.com Cc: Pavel Tatashin pavel.tatashin@microsoft.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Dan Williams dan.j.williams@intel.com Cc: Oscar Salvador osalvador@suse.de Cc: YASUAKI ISHIMATSU yasu.isimatu@gmail.com Cc: Mathieu Malaterre malat@debian.org Cc: John Allen jallen@linux.vnet.ibm.com Cc: Jonathan Corbet corbet@lwn.net Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Nathan Fontenot nfont@linux.vnet.ibm.com Cc: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/memory.c | 13 +------------ mm/memory_hotplug.c | 28 ++++++++++++++++++++-------- 2 files changed, 21 insertions(+), 20 deletions(-)
diff --git a/drivers/base/memory.c b/drivers/base/memory.c index 07901cacfec63..0f8e77f78cc80 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -228,7 +228,6 @@ static bool pages_correctly_probed(unsigned long start_pfn) /* * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is * OK to have direct references to sparsemem variables in here. - * Must already be protected by mem_hotplug_begin(). */ static int memory_block_action(unsigned long phys_index, unsigned long action, int online_type) @@ -294,7 +293,6 @@ static int memory_subsys_online(struct device *dev) if (mem->online_type < 0) mem->online_type = MMOP_ONLINE_KEEP;
- /* Already under protection of mem_hotplug_begin() */ ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
/* clear online_type */ @@ -341,19 +339,11 @@ store_mem_state(struct device *dev, goto err; }
- /* - * Memory hotplug needs to hold mem_hotplug_begin() for probe to find - * the correct memory block to online before doing device_online(dev), - * which will take dev->mutex. Take the lock early to prevent an - * inversion, memory_subsys_online() callbacks will be implemented by - * assuming it's already protected. - */ - mem_hotplug_begin(); - switch (online_type) { case MMOP_ONLINE_KERNEL: case MMOP_ONLINE_MOVABLE: case MMOP_ONLINE_KEEP: + /* mem->online_type is protected by device_hotplug_lock */ mem->online_type = online_type; ret = device_online(&mem->dev); break; @@ -364,7 +354,6 @@ store_mem_state(struct device *dev, ret = -EINVAL; /* should never happen */ }
- mem_hotplug_done(); err: unlock_device_hotplug();
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 0db85bffa3892..3a0a87e7c40ad 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -846,7 +846,6 @@ static struct zone * __meminit move_pfn_range(int online_type, int nid, return zone; }
-/* Must be protected by mem_hotplug_begin() or a device_lock */ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type) { unsigned long flags; @@ -858,6 +857,8 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ struct memory_notify arg; struct memory_block *mem;
+ mem_hotplug_begin(); + /* * We can't use pfn_to_nid() because nid might be stored in struct page * which is not yet initialized. Instead, we find nid from memory block. @@ -923,6 +924,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
if (onlined_pages) memory_notify(MEM_ONLINE, &arg); + mem_hotplug_done(); return 0;
failed_addition: @@ -930,6 +932,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ (unsigned long long) pfn << PAGE_SHIFT, (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1); memory_notify(MEM_CANCEL_ONLINE, &arg); + mem_hotplug_done(); return ret; } #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */ @@ -1134,20 +1137,20 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online) /* create new memmap entry */ firmware_map_add_hotplug(start, start + size, "System RAM");
+ /* device_online() will take the lock when calling online_pages() */ + mem_hotplug_done(); + /* online pages if requested */ if (online) walk_memory_range(PFN_DOWN(start), PFN_UP(start + size - 1), NULL, online_memory_block);
- goto out; - + return ret; error: /* rollback pgdat allocation and others */ if (new_node) rollback_node_hotadd(nid); memblock_remove(start, size); - -out: mem_hotplug_done(); return ret; } @@ -1614,10 +1617,16 @@ static int __ref __offline_pages(unsigned long start_pfn, return -EINVAL; if (!IS_ALIGNED(end_pfn, pageblock_nr_pages)) return -EINVAL; + + mem_hotplug_begin(); + /* This makes hotplug much easier...and readable. we assume this for now. .*/ - if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, &valid_end)) + if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start, + &valid_end)) { + mem_hotplug_done(); return -EINVAL; + }
zone = page_zone(pfn_to_page(valid_start)); node = zone_to_nid(zone); @@ -1626,8 +1635,10 @@ static int __ref __offline_pages(unsigned long start_pfn, /* set above range as isolated */ ret = start_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE, true); - if (ret) + if (ret) { + mem_hotplug_done(); return ret; + }
arg.start_pfn = start_pfn; arg.nr_pages = nr_pages; @@ -1698,6 +1709,7 @@ static int __ref __offline_pages(unsigned long start_pfn, writeback_set_ratelimit();
memory_notify(MEM_OFFLINE, &arg); + mem_hotplug_done(); return 0;
failed_removal: @@ -1707,10 +1719,10 @@ static int __ref __offline_pages(unsigned long start_pfn, memory_notify(MEM_CANCEL_OFFLINE, &arg); /* pushback to free area */ undo_isolate_page_range(start_pfn, end_pfn, MIGRATE_MOVABLE); + mem_hotplug_done(); return ret; }
-/* Must be protected by mem_hotplug_begin() or a device_lock */ int offline_pages(unsigned long start_pfn, unsigned long nr_pages) { return __offline_pages(start_pfn, start_pfn + nr_pages);