Commit-ID: 98fe3633c5a44e5ee3d642907739eb0210407886
Gitweb: http://git.kernel.org/tip/98fe3633c5a44e5ee3d642907739eb0210407886
Author: Jérôme Glisse <jglisse@xxxxxxxxxx>
AuthorDate: Sat, 24 Jun 2017 14:05:14 -0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 26 Jun 2017 11:44:19 +0200
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@xxxxxxxxxx>
[ Clarified the changelog and the code comments. ]
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/20170624180514.3821-1-jglisse@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/mm/init_64.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 95651dc..0a59daf 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -990,7 +990,13 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end,
pud_base = pud_offset(p4d, 0);
remove_pud_table(pud_base, addr, next, direct);
- free_pud_table(pud_base, p4d);
+ /*
+ * For 4-level page tables we do not want to free PUDs, but in the
+ * 5-level case we should free them. This code will have to change
+ * to adapt for boot-time switching between 4 and 5 level page tables.
+ */
+ if (CONFIG_PGTABLE_LEVELS == 5)
+ free_pud_table(pud_base, p4d);
}
if (direct)
--
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