On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote:
> xen_mm_pin_all()/unpin_all() are used to implement full guest instance
> suspend/restore. It's a stop-all method that needs to iterate through
> all allocated pgds in the system to fix them up for Xen's use.
>
> This code uses pgd_list, probably because it was an easy interface.
>
> But we want to remove the pgd_list, so convert the code over to walk
> all tasks in the system. This is an equivalent method.
>
> (As I don't use Xen this is was only build tested.)
In which case it seems extra important to copy the appropriate
maintainers, which I've done here.
Ian.
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Brian Gerst <brgerst@xxxxxxxxx>
> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Waiman Long <Waiman.Long@xxxxxx>
> Cc: linux-mm@xxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> arch/x86/xen/mmu.c | 51 ++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 38 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index dd151b2045b0..70a3df5b0b54 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -853,15 +853,27 @@ static void xen_pgd_pin(struct mm_struct *mm)
> */
> void xen_mm_pin_all(void)
> {
> - struct page *page;
> + struct task_struct *g, *p;
>
> - spin_lock(&pgd_lock);
> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list iteration: */
>
> - list_for_each_entry(page, &pgd_list, lru) {
> - if (!PagePinned(page)) {
> - __xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
> - SetPageSavePinned(page);
> + for_each_process_thread(g, p) {
> + struct mm_struct *mm;
> + struct page *page;
> + pgd_t *pgd;
> +
> + task_lock(p);
> + mm = p->mm;
> + if (mm) {
> + pgd = mm->pgd;
> + page = virt_to_page(pgd);
> +
> + if (!PagePinned(page)) {
> + __xen_pgd_pin(&init_mm, pgd);
> + SetPageSavePinned(page);
> + }
> }
> + task_unlock(p);
> }
>
> spin_unlock(&pgd_lock);
> @@ -967,19 +979,32 @@ static void xen_pgd_unpin(struct mm_struct *mm)
> */
> void xen_mm_unpin_all(void)
> {
> - struct page *page;
> + struct task_struct *g, *p;
>
> - spin_lock(&pgd_lock);
> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list iteration: */
>
> - list_for_each_entry(page, &pgd_list, lru) {
> - if (PageSavePinned(page)) {
> - BUG_ON(!PagePinned(page));
> - __xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
> - ClearPageSavePinned(page);
> + for_each_process_thread(g, p) {
> + struct mm_struct *mm;
> + struct page *page;
> + pgd_t *pgd;
> +
> + task_lock(p);
> + mm = p->mm;
> + if (mm) {
> + pgd = mm->pgd;
> + page = virt_to_page(pgd);
> +
> + if (PageSavePinned(page)) {
> + BUG_ON(!PagePinned(page));
> + __xen_pgd_unpin(&init_mm, pgd);
> + ClearPageSavePinned(page);
> + }
> }
> + task_unlock(p);
> }
>
> spin_unlock(&pgd_lock);
> + rcu_read_unlock();
> }
>
> static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
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