• David Hildenbrand's avatar
    mm/memory_hotplug: make add_memory() take the device_hotplug_lock · 8df1d0e4
    David Hildenbrand authored
    add_memory() currently does not take the device_hotplug_lock, however
    is aleady called under the lock from
    	arch/powerpc/platforms/pseries/hotplug-memory.c
    	drivers/acpi/acpi_memhotplug.c
    to synchronize against CPU hot-remove and similar.
    
    In general, we should hold the device_hotplug_lock when adding memory to
    synchronize against online/offline request (e.g.  from user space) - which
    already resulted in lock inversions due to device_lock() and
    mem_hotplug_lock - see 30467e0b ("mm, hotplug: fix concurrent memory
    hot-add deadlock").  add_memory()/add_memory_resource() will create memory
    block devices, so this really feels like the right thing to do.
    
    Holding the device_hotplug_lock makes sure that a memory block device
    can really only be accessed (e.g. via .online/.state) from user space,
    once the memory has been fully added to the system.
    
    The lock is not held yet in
    	drivers/xen/balloon.c
    	arch/powerpc/platforms/powernv/memtrace.c
    	drivers/s390/char/sclp_cmd.c
    	drivers/hv/hv_balloon.c
    So, let's either use the locked variants or take the lock.
    
    Don't export add_memory_resource(), as it once was exported to be used by
    XEN, which is never built as a module.  If somebody requires it, we also
    have to export a locked variant (as device_hotplug_lock is never
    exported).
    
    Link: http://lkml.kernel.org/r/20180925091457.28651-3-david@redhat.comSigned-off-by: David Hildenbrand's avatarDavid Hildenbrand <david@redhat.com>
    Reviewed-by: default avatarPavel Tatashin <pavel.tatashin@microsoft.com>
    Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
    Reviewed-by: default avatarRashmica Gupta <rashmica.g@gmail.com>
    Reviewed-by: default avatarOscar 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: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
    Cc: John Allen <jallen@linux.vnet.ibm.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Mathieu Malaterre <malat@debian.org>
    Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
    Cc: YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>
    Cc: Balbir Singh <bsingharora@gmail.com>
    Cc: Haiyang Zhang <haiyangz@microsoft.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Kate Stewart <kstewart@linuxfoundation.org>
    Cc: "K. Y. Srinivasan" <kys@microsoft.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Michael Neuling <mikey@neuling.org>
    Cc: Philippe Ombredanne <pombredanne@nexb.com>
    Cc: Stephen Hemminger <sthemmin@microsoft.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8df1d0e4
memory_hotplug.h 10.6 KB