On 03/29/2018 08:42 PM, Matthew Wilcox wrote:
> From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
>
> As with shmem_tag_pins(), hold the lock around the entire loop instead
> of acquiring & dropping it for each entry we're going to untag.
>
> Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Same comments as with with the previous shmem_tag_pins patch.
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
--
Mike Kravetz
> ---
> mm/memfd.c | 61 +++++++++++++++++++++++++------------------------------------
> 1 file changed, 25 insertions(+), 36 deletions(-)
>
> diff --git a/mm/memfd.c b/mm/memfd.c
> index 3b299d72df78..0e0835e63af2 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -64,9 +64,7 @@ static void shmem_tag_pins(struct address_space *mapping)
> */
> static int shmem_wait_for_pins(struct address_space *mapping)
> {
> - struct radix_tree_iter iter;
> - void __rcu **slot;
> - pgoff_t start;
> + XA_STATE(xas, &mapping->i_pages, 0);
> struct page *page;
> int error, scan;
>
> @@ -74,7 +72,9 @@ static int shmem_wait_for_pins(struct address_space *mapping)
>
> error = 0;
> for (scan = 0; scan <= LAST_SCAN; scan++) {
> - if (!radix_tree_tagged(&mapping->i_pages, SHMEM_TAG_PINNED))
> + unsigned int tagged = 0;
> +
> + if (!xas_tagged(&xas, SHMEM_TAG_PINNED))
> break;
>
> if (!scan)
> @@ -82,45 +82,34 @@ static int shmem_wait_for_pins(struct address_space *mapping)
> else if (schedule_timeout_killable((HZ << scan) / 200))
> scan = LAST_SCAN;
>
> - start = 0;
> - rcu_read_lock();
> - radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter,
> - start, SHMEM_TAG_PINNED) {
> -
> - page = radix_tree_deref_slot(slot);
> - if (radix_tree_exception(page)) {
> - if (radix_tree_deref_retry(page)) {
> - slot = radix_tree_iter_retry(&iter);
> - continue;
> - }
> -
> - page = NULL;
> - }
> -
> - if (page &&
> - page_count(page) - page_mapcount(page) != 1) {
> - if (scan < LAST_SCAN)
> - goto continue_resched;
> -
> + xas_set(&xas, 0);
> + xas_lock_irq(&xas);
> + xas_for_each_tag(&xas, page, ULONG_MAX, SHMEM_TAG_PINNED) {
> + bool clear = true;
> + if (xa_is_value(page))
> + continue;
> + if (page_count(page) - page_mapcount(page) != 1) {
> /*
> * On the last scan, we clean up all those tags
> * we inserted; but make a note that we still
> * found pages pinned.
> */
> - error = -EBUSY;
> - }
> -
> - xa_lock_irq(&mapping->i_pages);
> - radix_tree_tag_clear(&mapping->i_pages,
> - iter.index, SHMEM_TAG_PINNED);
> - xa_unlock_irq(&mapping->i_pages);
> -continue_resched:
> - if (need_resched()) {
> - slot = radix_tree_iter_resume(slot, &iter);
> - cond_resched_rcu();
> + if (scan == LAST_SCAN)
> + error = -EBUSY;
> + else
> + clear = false;
> }
> + if (clear)
> + xas_clear_tag(&xas, SHMEM_TAG_PINNED);
> + if (++tagged % XA_CHECK_SCHED)
> + continue;
> +
> + xas_pause(&xas);
> + xas_unlock_irq(&xas);
> + cond_resched();
> + xas_lock_irq(&xas);
> }
> - rcu_read_unlock();
> + xas_unlock_irq(&xas);
> }
>
> return error;
>
