x86/mm/hotplug: Fix BUG_ON() after hot-remove by not freeing PUD
authorJérôme Glisse <jglisse@redhat.com>
Sat, 24 Jun 2017 18:05:14 +0000 (14:05 -0400)
committerIngo Molnar <mingo@kernel.org>
Mon, 26 Jun 2017 09:44:19 +0000 (11:44 +0200)
commit98fe3633c5a44e5ee3d642907739eb0210407886
tree3408d8dfefe07787adc5bb32946b2a0ae22167e2
parentc0bc126f97fb929b3ae02c1c62322645d70eb408
x86/mm/hotplug: Fix BUG_ON() after hot-remove by not freeing PUD

Since commit:

  af2cf278ef4f ("x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()")

we no longer free PUDs so that we do not have to synchronize
all PGDs on hot-remove/vfree().

But the new 5-level page table patchset reverted that for 4-level
page tables, in the following commit:

  f2a6a7050109: ("x86: Convert the rest of the code to support p4d_t")

This patch restores the damage and disables free_pud() if we are in the
4-level page table case, thus avoiding BUG_ON() after hot-remove.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
[ Clarified the changelog and the code comments. ]
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170624180514.3821-1-jglisse@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/mm/init_64.c