Unfortunately, p?d_alloc() and p?d_free() are not pair!! If p?d_alloc()
succeed, they may be used, so in the next failure, we have to skip them
to let exit_mmap() or do_munmap() to process it.
According to "Documentation/vm/locking", 'mm->page_table_lock' is for
using vma list, so not need it when its related vmas are detached or
unmapped from using vma list.
The related work flow:
exit_mmap() ->
unmap_vmas(); /* so not need mm->page_table_lock */
free_pgtables();
do_munmap()->
detach_vmas_to_be_unmapped(); /* so not need mm->page_table_lock */
unmap_region() ->
free_pgtables();
free_pgtables() ->
free_pgd_range() ->
free_pud_range() ->
free_pmd_range() ->
free_pte_range() ->
pmd_clear();
pte_free_tlb();
pud_clear();
pmd_free_tlb();
pgd_clear();
pud_free_tlb();
Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
---
arch/um/kernel/skas/mmu.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 007d550..3fd1951 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -40,9 +40,9 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
return 0;
out_pte:
- pmd_free(mm, pmd);
+ /* used by mm->pgd->pud, will free in do_munmap() or exit_mmap() */
out_pmd:
- pud_free(mm, pud);
+ /* used by mm->pgd, will free in do_munmap() or exit_mmap() */
out:
return -ENOMEM;
}
--
1.7.7.6
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