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SubjectRe: [PATCH 2/4] mremap: don't do mm_populate(new_addr) on failure
On Sat, 20 Jun 2015, Oleg Nesterov wrote:

> move_vma() sets *locked even if move_page_tables() or ->mremap()
> fails, change sys_mremap() to check "ret & ~PAGE_MASK".
>
> I think we should simply remove the VM_LOCKED code in move_vma(),
> that is why this patch doesn't change move_vma(). But this needs
> more cleanups.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
> mm/mremap.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/mm/mremap.c b/mm/mremap.c
> index a6306bc..492721c 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -574,8 +574,10 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
> ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
> }
> out:
> - if (ret & ~PAGE_MASK)
> + if (ret & ~PAGE_MASK) {
> vm_unacct_memory(charged);
> + locked = 0;
> + }
> up_write(&current->mm->mmap_sem);
> if (locked && new_len > old_len)
> mm_populate(new_addr + old_len, new_len - old_len);

Perhaps I'm looking at the wrong tree (next-20150630), but why does
setting locked to 0 here matter if it's unreferenced?


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