lkml.org 
[lkml]   [2019]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] mm/swap: Fix release_pages() when releasing devmap pages
Sorry for a late reply.

On Wed 05-06-19 14:49:22, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> release_pages() is an optimized version of a loop around put_page().
> Unfortunately for devmap pages the logic is not entirely correct in
> release_pages(). This is because device pages can be more than type
> MEMORY_DEVICE_PUBLIC. There are in fact 4 types, private, public, FS
> DAX, and PCI P2PDMA. Some of these have specific needs to "put" the
> page while others do not.
>
> This logic to handle any special needs is contained in
> put_devmap_managed_page(). Therefore all devmap pages should be
> processed by this function where we can contain the correct logic for a
> page put.
>
> Handle all device type pages within release_pages() by calling
> put_devmap_managed_page() on all devmap pages. If
> put_devmap_managed_page() returns true the page has been put and we
> continue with the next page. A false return of
> put_devmap_managed_page() means the page did not require special
> processing and should fall to "normal" processing.
>
> This was found via code inspection while determining if release_pages()
> and the new put_user_pages() could be interchangeable.[1]

This is much more clear than the previous version I've looked at. Thanks
a lot!
>
> [1] https://lore.kernel.org/lkml/20190523172852.GA27175@iweiny-DESK2.sc.intel.com/
>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Acked-by: Michal Hocko <mhocko@suse.com>

>
> ---
> Changes from V3:
> Update comment to the one provided by John
>
> Changes from V2:
> Update changelog for more clarity as requested by Michal
> Update comment WRT "failing" of put_devmap_managed_page()
>
> Changes from V1:
> Add comment clarifying that put_devmap_managed_page() can still
> fail.
> Add Reviewed-by tags.
>
> mm/swap.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/mm/swap.c b/mm/swap.c
> index 7ede3eddc12a..607c48229a1d 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -740,15 +740,20 @@ void release_pages(struct page **pages, int nr)
> if (is_huge_zero_page(page))
> continue;
>
> - /* Device public page can not be huge page */
> - if (is_device_public_page(page)) {
> + if (is_zone_device_page(page)) {
> if (locked_pgdat) {
> spin_unlock_irqrestore(&locked_pgdat->lru_lock,
> flags);
> locked_pgdat = NULL;
> }
> - put_devmap_managed_page(page);
> - continue;
> + /*
> + * ZONE_DEVICE pages that return 'false' from
> + * put_devmap_managed_page() do not require special
> + * processing, and instead, expect a call to
> + * put_page_testzero().
> + */
> + if (put_devmap_managed_page(page))
> + continue;
> }
>
> page = compound_head(page);
> --
> 2.20.1
>

--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2019-06-21 10:12    [W:0.134 / U:0.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site