From: Junaid Shahid <junaids@google.com>
To: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, andreslc@google.com, gthelen@google.com,
mpatocka@redhat.com, vbabka@suse.cz,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params()
Date: Thu, 18 May 2017 19:50:46 -0700 [thread overview]
Message-ID: <1508444.i5EqlA1upv@js-desktop.svl.corp.google.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1705181338090.132717@chino.kir.corp.google.com>
(Adding back the correct linux-mm email address and also adding linux-kernel.)
On Thursday, May 18, 2017 01:41:33 PM David Rientjes wrote:
> On Thu, 18 May 2017, Michal Hocko wrote:
>
> > On Thu 18-05-17 11:50:40, Junaid Shahid wrote:
> > > d224e9381897 (drivers/md/dm-ioctl.c: use kvmalloc rather than opencoded
> > > variant) left out the __GFP_HIGH flag when converting from __vmalloc to
> > > kvmalloc. This can cause the IOCTL to fail in some low memory situations
> > > where it wouldn't have failed earlier. This patch adds it back to avoid
> > > any potential regression.
> >
> > The code previously used __GFP_HIGH only for the vmalloc fallback and
> > that doesn't make that much sense with the current implementation
> > because vmalloc does order-0 pages and those do not really fail and the
> > oom killer is invoked to free memory.
> >
>
> Order-0 pages certainly do fail, there is not an infinite amount of memory
> nor is there a specific exemption to allow order-0 memory to be alloctable
> below watermarks without this gfp flag. OOM kill is the last thing we
> want for these allocations since they are very temporary.
>
> > There is no reason to access memory reserves from this context.
> >
>
> Let's ask Mikulas, who changed this from PF_MEMALLOC to __GFP_HIGH,
> assuming there was a reason to do it in the first place in two different
> ways.
>
> This decision is up to the device mapper maintainers.
>
> > > Signed-off-by: Junaid Shahid <junaids@google.com>
> > > ---
> > > drivers/md/dm-ioctl.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > > index 0555b4410e05..bacad7637a56 100644
> > > --- a/drivers/md/dm-ioctl.c
> > > +++ b/drivers/md/dm-ioctl.c
> > > @@ -1715,7 +1715,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
> > > */
> > > dmi = NULL;
> > > noio_flag = memalloc_noio_save();
> > > - dmi = kvmalloc(param_kernel->data_size, GFP_KERNEL);
> > > + dmi = kvmalloc(param_kernel->data_size, GFP_KERNEL | __GFP_HIGH);
> > > memalloc_noio_restore(noio_flag);
> > >
> > > if (!dmi) {
next parent reply other threads:[~2017-05-19 2:50 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170518185040.108293-1-junaids@google.com>
[not found] ` <20170518190406.GB2330@dhcp22.suse.cz>
[not found] ` <alpine.DEB.2.10.1705181338090.132717@chino.kir.corp.google.com>
2017-05-19 2:50 ` Junaid Shahid [this message]
2017-05-19 7:46 ` [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko
2017-05-19 23:43 ` Mikulas Patocka
2017-05-22 9:37 ` Michal Hocko
2017-05-22 12:00 ` Mikulas Patocka
2017-05-22 12:09 ` Michal Hocko
2017-05-22 14:52 ` Mikulas Patocka
2017-05-22 15:03 ` Michal Hocko
2017-05-22 18:04 ` Mike Snitzer
2017-05-22 20:35 ` David Rientjes
2017-05-22 23:35 ` Mike Snitzer
2017-05-23 6:05 ` Michal Hocko
2017-05-23 16:44 ` Mikulas Patocka
2017-05-25 8:58 ` Michal Hocko
2017-05-23 6:49 ` Michal Hocko
[not found] ` <alpine.LRH.2.02.1705191949340.17646@file01.intranet.prod.int.rdu2.redhat.com>
[not found] ` <20170520083412.GD11925@dhcp22.suse.cz>
2017-05-20 19:00 ` [PATCH] " Mikulas Patocka
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