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SubjectRe: [PATCH] memcg: set page->private before calling swap_readpage
On Wed, Mar 17, 2021 at 06:59:59PM -0700, Shakeel Butt wrote:
> The function swap_readpage() (and other functions it call) extracts swap
> entry from page->private. However for SWP_SYNCHRONOUS_IO, the kernel
> skips the swapcache and thus we need to manually set the page->private
> with the swap entry before calling swap_readpage().
>
> Signed-off-by: Shakeel Butt <shakeelb@google.com>
> Reported-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>
> Andrew, please squash this into "memcg: charge before adding to
> swapcache on swapin" patch.
>
> mm/memory.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index aefd158ae1ea..b6f3410b5902 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3324,7 +3324,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> workingset_refault(page, shadow);
>
> lru_cache_add(page);
> +
> + /* To provide entry to swap_readpage() */
> + set_page_private(page, entry.val);
> swap_readpage(page, true);
> + set_page_private(page, 0);

Yes, this seems to fix it. Thanks a lot!

Tested-by: Heiko Carstens <hca@linux.ibm.com>

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