Re: [PATCH 2/3] mm: fix possible incorrect return value of migrate_pages() syscall

[Michal Nazarewicz]

Joonsoo Kim <js1304@xxxxxxxxx> writes:
> do_migrate_pages() can return the number of pages not migrated.
> Because migrate_pages() syscall return this value directly,
> migrate_pages() syscall may return the number of pages not migrated.
> In fail case in migrate_pages() syscall, we should return error value.
> So change err to -EIO
>
> Additionally, Correct comment above do_migrate_pages()
>
> Signed-off-by: Joonsoo Kim <js1304@xxxxxxxxx>
> Cc: Sasha Levin <levinsasha928@xxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>

Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>

> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 1d771e4..f7df271 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -948,7 +948,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>   * Move pages between the two nodesets so as to preserve the physical
>   * layout as much as possible.
>   *
> - * Returns the number of page that could not be moved.
> + * Returns error or the number of pages not migrated.
>   */
>  int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
>  		     const nodemask_t *to, int flags)
> @@ -1382,6 +1382,8 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
>  
>  	err = do_migrate_pages(mm, old, new,
>  		capable(CAP_SYS_NICE) ? MPOL_MF_MOVE_ALL : MPOL_MF_MOVE);
> +	if (err > 0)
> +		err = -EIO;
>  
>  	mmput(mm);
>  out:

-- 
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 .o. | Liege of Serenly Enlightened Majesty of       o' \,=./ `o
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