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Re: [PATCH 2/4] mremap: don't do mm_populate(new_addr) on failure

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  Re: [PATCH 2/4] mremap: don't do mm_populate(new_addr) on failure David Rientjes <rientjes@google.com> - 2015-07-01 23:50 +0200
    Re: [PATCH 2/4] mremap: don't do mm_populate(new_addr) on failure Oleg Nesterov <oleg@redhat.com> - 2015-07-02 00:50 +0200

#1175567 — Re: [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);

Acked-by: David Rientjes <rientjes@google.com>

Might be cleaner to rename this to "populate" in sys_mremap() and set it 
to false in the previous old_len >= new_len conditional and remove the 
check here for new_len > old_len.
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#1175590

On 07/01, David Rientjes wrote:
>
> 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);
>
> Acked-by: David Rientjes <rientjes@google.com>

Thanks! I am resending this series with your acks applies.

Plus another patche which was already acked but ignored anyway ;)

> Might be cleaner to rename this to "populate" in sys_mremap() and set it
> to false in the previous old_len >= new_len conditional and remove the
> check here for new_len > old_len.

Oh, this needs much more cleanups. Imo the whole VM_LOCKED logic in these
paths is ugly and confusing. move_vma() shouldn't look at VM_LOCKED at all,
mremap_to() should not duplicate the vma_to_resize/move_vma code, etc.

Oleg.

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