NAK: [SRU][F][PATCH 1/1] s390/qeth: use memory reserves to back RX buffers

[Thadeu Lima de Souza Cascardo]

On Mon, Feb 07, 2022 at 04:15:04PM +0100, Krzysztof Kozlowski wrote:
> On 04/02/2022 15:29, Krzysztof Kozlowski wrote:
> > On 04/02/2022 14:49, Thadeu Lima de Souza Cascardo wrote:
> >> On Fri, Feb 04, 2022 at 10:29:21AM +0100, Krzysztof Kozlowski wrote:
> >>> On 04/02/2022 07:47, frank.heimes at canonical.com wrote:
> >>>> From: Julian Wiedmann <jwi at linux.ibm.com>
> >>>>
> >>>> BugLink: https://bugs.launchpad.net/bugs/1959529
> >>>>
> >>>> Use dev_alloc_page() for backing the RX buffers with pages. This way we
> >>>> pick up __GFP_MEMALLOC.
> >>>>
> >>>> Signed-off-by: Julian Wiedmann <jwi at linux.ibm.com>
> >>>> Signed-off-by: David S. Miller <davem at davemloft.net>
> >>>> (backported from commit 714c9108851743bb718fbc1bfb81290f12a53854)
> >>>> Signed-off-by: Alexandra Winter <wintera at linux.ibm.com>
> >>>> Signed-off-by: Frank Heimes <frank.heimes at canonical.com>
> >>>> ---
> >>>>  drivers/s390/net/qeth_core_main.c | 4 ++--
> >>>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
> >>>> index ec8c7a640d9e..61372e5c279b 100644
> >>>> --- a/drivers/s390/net/qeth_core_main.c
> >>>> +++ b/drivers/s390/net/qeth_core_main.c
> >>>> @@ -227,7 +227,7 @@ static int qeth_alloc_buffer_pool(struct qeth_card *card)
> >>>>  			return -ENOMEM;
> >>>>  		}
> >>>>  		for (j = 0; j < QETH_MAX_BUFFER_ELEMENTS(card); ++j) {
> >>>> -			ptr = (void *) __get_free_page(GFP_KERNEL);
> >>>> +			ptr = (void *) __dev_alloc_page(GFP_KERNEL);
> >>>
> >>
> >> Or since the whole point is to use __GPF_MEMALLOC, simply do:
> >>
> > 
> > It is not exact equivalent of __dev_alloc_page (__get_free_page() picks
> > closest NUMA node, __dev_alloc_page() loads entire NUMA policy and
> > chooses node according to it) , but I guess the differences here do not
> > matter.
> > 
> > The MEMALLOC, which allows using emergency memory pools and should not
> > be used outside of memory management subsystem or outside paths freeing
> > memory, seems a weird solution to reported problem of lack of memory.
> > The Bug report is saying that memory allocation failed, without too many
> > details so probably because of lack of memory in the system. :) This is
> > a RX buffer. Allocating a generic network RX buffer in case of
> > out-of-memory situation from emergency pools does not fit into MEMALLOC
> > purpose...
> > 
> > However if IBM feels it is proper approach for their problem, let's go
> > with simply MEMALLOC flag, like Thadeu suggested.
> > 
> 
> Alexandra Winter from IBM proposed to pick up only second part of the
> patch which looks correct. This fixes their issue, see:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1959529/comments/7
> 
> However picking up only half of a stable commit will confuse some stable
> scripts (e.g. stable-commit-in-tree from stable-tools).
> 
> Since we skip parts of the commit, I propose to bring it as "UBUNTU:
> SAUCE:" patch by us, with a similar title/explanation, but not exactly
> the same.
> 
> Any comments on such approach?
> 
> Best regards,
> Krzysztof

I would rather backport the other hunk too, by just adding the MEMALLOC
flag.

Cascardo.