diff mbox series

[2/2] swap: Deal with PTE mapped THP when unuse PTE

Message ID 20181211084609.19553-2-ying.huang@intel.com (mailing list archive)
State New, archived
Headers show
Series [1/2] swap: Fix general protection fault when swapoff | expand

Commit Message

Huang, Ying Dec. 11, 2018, 8:46 a.m. UTC
A PTE swap entry may map to a normal swap slot inside a huge swap
cluster.  To free the huge swap cluster and the corresponding
THP (transparent huge page), all PTE swap entry mappings need to be
unmapped.  The original implementation only checks current PTE swap
entry mapping, this is fixed via calling try_to_free_swap() instead,
which will check all PTE swap mappings inside the huge swap cluster.

This fix could be folded into the patch: mm, swap: rid swapoff of
quadratic complexity in -mm patchset.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Vineeth Remanan Pillai <vpillai@digitalocean.com>
Cc: Kelley Nielsen <kelleynnn@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
---
 mm/swapfile.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

William Kucharski Dec. 11, 2018, 2:32 p.m. UTC | #1
> ---
> mm/swapfile.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 7464d0a92869..9e6da494781f 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1921,10 +1921,8 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> 			goto out;
> 		}
> 
> -		if (PageSwapCache(page) && (swap_count(*swap_map) == 0))
> -			delete_from_swap_cache(compound_head(page));
> +		try_to_free_swap(page);
> 
> -		SetPageDirty(page);
> 		unlock_page(page);
> 		put_page(page);
> 
> -- 
> 2.18.1
> 

Since try_to_free_swap() can return 0 under certain error conditions, you should check
check for a return status of 1 before calling unlock_page() and put_page().

Reviewed-by: William Kucharski <william.kucharski@oracle.com>
diff mbox series

Patch

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7464d0a92869..9e6da494781f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1921,10 +1921,8 @@  static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 			goto out;
 		}
 
-		if (PageSwapCache(page) && (swap_count(*swap_map) == 0))
-			delete_from_swap_cache(compound_head(page));
+		try_to_free_swap(page);
 
-		SetPageDirty(page);
 		unlock_page(page);
 		put_page(page);