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

[Sergey Senozhatsky]

On (22/11/21 22:16), Johannes Weiner wrote:
> 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@xxxxxxxxxxxx>
> > ---
> >  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?

Yup, you patch it in https://lore.kernel.org/lkml/20221119001536.2086599-2-nphamcs@xxxxxxxxx/
and I guess it's there just by accident. We probably want a separate
patch instead that touches those GFP_ATOMIC allocations in both places.

So I have it like this at present

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