| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <49b2c2de-5d50-1f61-5ddf-e72c52017534@suse.cz>
Date: Fri, 6 Jan 2017 13:09:36 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Michal Hocko <mhocko@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: David Rientjes <rientjes@...gle.com>, Mel Gorman <mgorman@...e.de>,
Johannes Weiner <hannes@...xchg.org>,
Al Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org,
LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
linux-security-module@...r.kernel.org, linux-ext4@...r.kernel.org,
Joe Perches <joe@...ches.com>,
Anatoly Stepanov <astepanov@...udlinux.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Mike Snitzer <snitzer@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH] mm: support __GFP_REPEAT in kvmalloc_node
On 01/04/2017 07:12 PM, Michal Hocko wrote:
> While checking opencoded users I've encountered that vhost code would
> really like to use kvmalloc with __GFP_REPEAT [1] so the following patch
> adds support for __GFP_REPEAT and converts both vhost users.
>
> So currently I am sitting on 3 patches. I will wait for more feedback -
> especially about potential split ups or cleanups few more days and then
> repost the whole series.
>
> [1] http://lkml.kernel.org/r/20170104150800.GO25453@dhcp22.suse.cz
> ---
> From 0b92e4d2e040524b878d4e7b9ee88fbad5284b33 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.com>
> Date: Wed, 4 Jan 2017 18:01:39 +0100
> Subject: [PATCH] mm: support __GFP_REPEAT in kvmalloc_node
>
> vhost code uses __GFP_REPEAT when allocating vhost_virtqueue resp.
> vhost_vsock because it would really like to prefer kmalloc to the
> vmalloc fallback - see 23cc5a991c7a ("vhost-net: extend device
> allocation to vmalloc") for more context. Michael Tsirkin has also
> noted:
> "
> __GFP_REPEAT overhead is during allocation time. Using vmalloc means all
> accesses are slowed down. Allocation is not on data path, accesses are.
> "
>
> Let's teach kvmalloc_node to handle __GFP_REPEAT properly. There are two
> things to be careful about. First we should prevent from the OOM killer
> and so have to involve __GFP_NORETRY by default and secondly override
> __GFP_REPEAT for !costly order requests as the __GFP_REPEAT is ignored
> for !costly orders.
>
> This patch shouldn't introduce any functional change.
Which is because the converted usages are always used for costly order,
right.
>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
> drivers/vhost/net.c | 9 +++------
> drivers/vhost/vsock.c | 9 +++------
> mm/util.c | 9 +++++++--
> 3 files changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 5dc34653274a..105cd04c7414 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -797,12 +797,9 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> struct vhost_virtqueue **vqs;
> int i;
>
> - n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> - if (!n) {
> - n = vmalloc(sizeof *n);
> - if (!n)
> - return -ENOMEM;
> - }
> + n = kvmalloc(sizeof *n, GFP_KERNEL | __GFP_REPEAT);
> + if (!n)
> + return -ENOMEM;
> vqs = kmalloc(VHOST_NET_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
> if (!vqs) {
> kvfree(n);
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index bbbf588540ed..7e0159867553 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -455,12 +455,9 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
> /* This struct is large and allocation could fail, fall back to vmalloc
> * if there is no other way.
> */
> - vsock = kzalloc(sizeof(*vsock), GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
> - if (!vsock) {
> - vsock = vmalloc(sizeof(*vsock));
> - if (!vsock)
> - return -ENOMEM;
> - }
> + vsock = kvmalloc(sizeof(*vsock), GFP_KERNEL | __GFP_REPEAT);
> + if (!vsock)
> + return -ENOMEM;
>
> vqs = kmalloc_array(ARRAY_SIZE(vsock->vqs), sizeof(*vqs), GFP_KERNEL);
> if (!vqs) {
> diff --git a/mm/util.c b/mm/util.c
> index 8e4ea6cbe379..a2bfb85e60e5 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -348,8 +348,13 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
> * Make sure that larger requests are not too disruptive - no OOM
> * killer and no allocation failure warnings as we have a fallback
> */
> - if (size > PAGE_SIZE)
> - kmalloc_flags |= __GFP_NORETRY | __GFP_NOWARN;
> + if (size > PAGE_SIZE) {
> + kmalloc_flags |= __GFP_NOWARN;
> +
> + if (!(kmalloc_flags & __GFP_REPEAT) ||
> + (size <= PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
> + kmalloc_flags |= __GFP_NORETRY;
I think this would be more understandable for me if it was written in
the opposite way, i.e. "if we have costly __GFP_REPEAT allocation, don't
use __GFP_NORETRY", but nevermind, seems correct to me wrt current
handling of both flags in the page allocator. And it serves as a good
argument to have this wrapper in mm/ as we are hopefully more likely to
keep it working as intended with future changes, than all the opencoded
variants.
Acked-by: Vlastimil Babka <vbabka@...e.cz>
> + }
>
> ret = kmalloc_node(size, kmalloc_flags, node);
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists