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SubjectRe: [PATCH 4/4] uprobes: __replace_page() needs munlock_vma_page()
* Oleg Nesterov <oleg@redhat.com> [2012-07-12 19:10:25]:

> Like do_wp_page(), __replace_page() should do munlock_vma_page()
> for the case when the old page still has other !VM_LOCKED mappings.
> Unfortunately this needs mm/internal.h.
>
> Also, move put_page() outside of ptl lock. This doesn't really
> matter but looks a bit better.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

One thing I wanted to check is, should we mlock the new page, i.e the
replacing page. It may not a good idea to mlock the new page
because then we can end up adding too many pages to the unevictable
list.

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> kernel/events/uprobes.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index fc1df43..aeea41b 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -32,6 +32,7 @@
> #include <linux/swap.h> /* try_to_free_swap */
> #include <linux/ptrace.h> /* user_enable_single_step */
> #include <linux/kdebug.h> /* notifier mechanism */
> +#include "../../mm/internal.h" /* munlock_vma_page */
>
> #include <linux/uprobes.h>
>
> @@ -141,7 +142,7 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
> pte_t *ptep;
> int err;
>
> - /* freeze PageSwapCache() for try_to_free_swap() below */
> + /* For try_to_free_swap() and munlock_vma_page() below */
> lock_page(page);
>
> err = -EAGAIN;
> @@ -164,9 +165,12 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
> page_remove_rmap(page);
> if (!page_mapped(page))
> try_to_free_swap(page);
> - put_page(page);
> pte_unmap_unlock(ptep, ptl);
>
> + if (vma->vm_flags & VM_LOCKED)
> + munlock_vma_page(page);
> + put_page(page);
> +
> err = 0;
> unlock:
> unlock_page(page);
> --
> 1.5.5.1
>



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