[6/8] mm/migrate.c: handle same node and add failure in the same way
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Message ID 20200119030636.11899-7-richardw.yang@linux.intel.com
State New
Headers show
Series
  • mm/migrate.c: cleanup on do_pages_move()
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Commit Message

Wei Yang Jan. 19, 2020, 3:06 a.m. UTC
When page is not queued for migration, there are two possible cases:

  * page already on the target node
  * failed to add to migration queue

Current code handle them differently, this leads to a behavior
inconsistency.

Usually for each page's status, we just do store for once. While for the
page already on the target node, we might store the node information for
twice:

  * once when we found the page is on the target node
  * second when moving the pages to target node successfully after above
    action

The reason is even we don't add the page to pagelist, but store_status()
does store in a range which still contains the page.

This patch handles these two cases in the same way to reduce this
inconsistency and also make the code a little easier to read.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 mm/migrate.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Comments

Michal Hocko Jan. 20, 2020, 10:01 a.m. UTC | #1
On Sun 19-01-20 11:06:34, Wei Yang wrote:
> When page is not queued for migration, there are two possible cases:
> 
>   * page already on the target node
>   * failed to add to migration queue
> 
> Current code handle them differently, this leads to a behavior
> inconsistency.
> 
> Usually for each page's status, we just do store for once. While for the
> page already on the target node, we might store the node information for
> twice:
> 
>   * once when we found the page is on the target node
>   * second when moving the pages to target node successfully after above
>     action
> 
> The reason is even we don't add the page to pagelist, but store_status()
> does store in a range which still contains the page.
> 
> This patch handles these two cases in the same way to reduce this
> inconsistency and also make the code a little easier to read.

Yeah, the improvement is really marginal. I do not feel strongly one way
or another.

> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>

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

> ---
>  mm/migrate.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 46a5697b7fc6..aee5aeb082c4 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1657,18 +1657,18 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>  		err = add_page_for_migration(mm, addr, current_node,
>  				&pagelist, flags & MPOL_MF_MOVE_ALL);
>  
> -		if (!err) {
> -			/* The page is already on the target node */
> -			err = store_status(status, i, current_node, 1);
> -			if (err)
> -				goto out_flush;
> -			continue;
> -		} else if (err > 0) {
> +		if (err > 0) {
>  			/* The page is successfully queued for migration */
>  			continue;
>  		}
>  
> -		err = store_status(status, i, err, 1);
> +		/*
> +		 * Two possible cases for err here:
> +		 * == 0: page is already on the target node, then store
> +		 *       current_node to status
> +		 * <  0: failed to add page to list, then store err to status
> +		 */
> +		err = store_status(status, i, err ? : current_node, 1);
>  		if (err)
>  			goto out_flush;
>  
> -- 
> 2.17.1
>

Patch
diff mbox series

diff --git a/mm/migrate.c b/mm/migrate.c
index 46a5697b7fc6..aee5aeb082c4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1657,18 +1657,18 @@  static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 		err = add_page_for_migration(mm, addr, current_node,
 				&pagelist, flags & MPOL_MF_MOVE_ALL);
 
-		if (!err) {
-			/* The page is already on the target node */
-			err = store_status(status, i, current_node, 1);
-			if (err)
-				goto out_flush;
-			continue;
-		} else if (err > 0) {
+		if (err > 0) {
 			/* The page is successfully queued for migration */
 			continue;
 		}
 
-		err = store_status(status, i, err, 1);
+		/*
+		 * Two possible cases for err here:
+		 * == 0: page is already on the target node, then store
+		 *       current_node to status
+		 * <  0: failed to add page to list, then store err to status
+		 */
+		err = store_status(status, i, err ? : current_node, 1);
 		if (err)
 			goto out_flush;