From: Michal Hocko <mhocko@kernel.org>
To: Bharath Vedartham <linux.bhar@gmail.com>
Cc: akpm@linux-foundation.org, vbabka@suse.cz, rientjes@google.com,
khalid.aziz@oracle.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: Remove VM_BUG_ON in __alloc_pages_node
Date: Wed, 5 Jun 2019 09:03:12 +0200 [thread overview]
Message-ID: <20190605070312.GB15685@dhcp22.suse.cz> (raw)
In-Reply-To: <20190605060229.GA9468@bharath12345-Inspiron-5559>
On Wed 05-06-19 11:32:29, Bharath Vedartham wrote:
> In __alloc_pages_node, there is a VM_BUG_ON on the condition (nid < 0 ||
> nid >= MAX_NUMNODES). Remove this VM_BUG_ON and add a VM_WARN_ON, if the
> condition fails and fail the allocation if an invalid NUMA node id is
> passed to __alloc_pages_node.
What is the motivation of the patch? VM_BUG_ON is not enabled by default
and your patch adds a branch to a really hot path. Why is this an
improvement for something that shouldn't happen in the first place?
>
> The check (nid < 0 || nid >= MAX_NUMNODES) also considers NUMA_NO_NODE
> as an invalid nid, but the caller of __alloc_pages_node is assumed to
> have checked for the case where nid == NUMA_NO_NODE.
>
> Signed-off-by: Bharath Vedartham <linux.bhar@gmail.com>
> ---
> include/linux/gfp.h | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 5f5e25f..075bdaf 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -480,7 +480,11 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
> static inline struct page *
> __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
> {
> - VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
> + if (nid < 0 || nid >= MAX_NUMNODES) {
> + VM_WARN_ON(nid < 0 || nid >= MAX_NUMNODES);
> + return NULL;
> + }
> +
> VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));
>
> return __alloc_pages(gfp_mask, order, nid);
> --
> 2.7.4
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-06-05 7:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 6:02 [PATCH] mm: Remove VM_BUG_ON in __alloc_pages_node Bharath Vedartham
2019-06-05 7:03 ` Michal Hocko [this message]
2019-06-05 13:07 ` Bharath Vedartham
2019-06-05 14:22 ` Michal Hocko
2019-06-05 15:55 ` Bharath Vedartham
2019-06-06 5:29 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190605070312.GB15685@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=khalid.aziz@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux.bhar@gmail.com \
--cc=rientjes@google.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).