Andrey Wagin reported crash on VM_BUG_ON() in pgtable_pmd_page_dtor()
with fallowing backtrace:
[<ffffffff8119427f>] free_pgd_range+0x2bf/0x410
[<ffffffff8119449e>] free_pgtables+0xce/0x120
[<ffffffff8119b900>] unmap_region+0xe0/0x120
[<ffffffff811a0036>] ? move_page_tables+0x526/0x6b0
[<ffffffff8119d6a9>] do_munmap+0x249/0x360
[<ffffffff811a0304>] move_vma+0x144/0x270
[<ffffffff811a07e9>] SyS_mremap+0x3b9/0x510
[<ffffffff8172d512>] system_call_fastpath+0x16/0x1b
The crash can be reproduce with this test case:
#define _GNU_SOURCE
#include <sys/mman.h>
#include <stdio.h>
#include <unistd.h>
#define MB (1024 * 1024UL)
#define GB (1024 * MB)
int main(int argc, char **argv)
{
char *p;
int i;
p = mmap((void *) GB, 10 * MB, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
for (i = 0; i < 10 * MB; i += 4096)
p[i] = 1;
mremap(p, 10 * MB, 10 * MB, MREMAP_FIXED | MREMAP_MAYMOVE, 2 * GB);
return 0;
}
Due to split PMD lock, we now store preallocated PTE tables for THP
pages per-PMD table. It means we need to move them to other PMD table
if huge PMD moved there.
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Reported-by: Andrey Vagin <ava...@openvz.org>
---
mm/huge_memory.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bccd5a628ea6..33a5dc492810 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1481,8 +1481,18 @@ int move_huge_pmd(struct vm_area_struct *vma, struct
vm_area_struct *new_vma,
pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
VM_BUG_ON(!pmd_none(*new_pmd));
set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
- if (new_ptl != old_ptl)
+ if (new_ptl != old_ptl) {
+ pgtable_t pgtable;
+
+ /*
+ * Move preallocated PTE page table if new_pmd is on
+ * different PMD page table.
+ */
+ pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
+ pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
+
spin_unlock(new_ptl);
+ }
spin_unlock(old_ptl);
}
out:
--
1.8.4.4
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