Re: [PATCH] zswap: do not allocate from atomic pool

Johannes Weiner
2022-11-22T03:16:08Z

On Tue, Nov 22, 2022 at 10:33:38AM +0900, Sergey Senozhatsky wrote:
> zswap_frontswap_load() should be called from preemptible
> context (we even call mutex_lock() there) and it does not
> look like we need to do GFP_ATOMIC allocaion for temp
> buffer there. Use GFP_KERNEL instead.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
> mm/zswap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 2d69c1d678fe..f6c89049cf70 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1314,7 +1314,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> }
>
> if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
> - tmp = kmalloc(entry->length, GFP_ATOMIC);
> + tmp = kmalloc(entry->length, GFP_KERNEL);

There is another one in zswap_writeback_entry() that seems equally
arbitrary. They came in through the same commit, with no further
explanation as to this choice. Do you want to pick that up too?