From: Feng Tang <feng.tang@intel.com>
To: Michal Hocko <mhocko@suse.com>,
Dave Hansen <dave.hansen@intel.com>,
Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
David Rientjes <rientjes@google.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Kravetz <mike.kravetz@oracle.com>,
Randy Dunlap <rdunlap@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>, Andi Kleen <ak@linux.intel.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v4 04/13] mm/mempolicy: allow preferred code to take a nodemask
Date: Mon, 19 Apr 2021 16:49:24 +0800 [thread overview]
Message-ID: <20210419084924.GA25519@shbuild999.sh.intel.com> (raw)
In-Reply-To: <YHbmS6R+CpSDWtAD@dhcp22.suse.cz>
On Wed, Apr 14, 2021 at 02:55:39PM +0200, Michal Hocko wrote:
> On Wed 17-03-21 11:40:01, Feng Tang wrote:
> > From: Dave Hansen <dave.hansen@linux.intel.com>
> >
> > Create a helper function (mpol_new_preferred_many()) which is usable
> > both by the old, single-node MPOL_PREFERRED and the new
> > MPOL_PREFERRED_MANY.
> >
> > Enforce the old single-node MPOL_PREFERRED behavior in the "new"
> > version of mpol_new_preferred() which calls mpol_new_preferred_many().
> >
> > v3:
> > * fix a stack overflow caused by emty nodemask (Feng)
> >
> > Link: https://lore.kernel.org/r/20200630212517.308045-5-ben.widawsky@intel.com
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > Signed-off-by: Feng Tang <feng.tang@intel.com>
> > ---
> > mm/mempolicy.c | 21 +++++++++++++++++++--
> > 1 file changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 1228d8e..6fb2cab 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -203,17 +203,34 @@ static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
> > return 0;
> > }
> >
> > -static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
> > +static int mpol_new_preferred_many(struct mempolicy *pol,
> > + const nodemask_t *nodes)
> > {
> > if (!nodes)
> > pol->flags |= MPOL_F_LOCAL; /* local allocation */
>
> Now you have confused me. I thought that MPOL_PREFERRED_MANY for NULL
> nodemask will be disallowed as it is effectively MPOL_PREFERRED aka
> MPOL_F_LOCAL. Or do I misread the code?
I think you are right, with current code, the 'nodes' can't be NULL for
MPOL_PREFERRED_MANY, we'll revisit this.
And I have to admit that I am confused by the current logic for MPOL_PREFERRED,
that the nodemask paramter changes between raw user input, empty nodes and NULL.
Maybe the following patch can make it more clear, as it doesn't play the
NULL nmask trick?
---
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index be160d4..9cabfca 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -200,12 +200,9 @@ static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
{
- if (!nodes)
- pol->flags |= MPOL_F_LOCAL; /* local allocation */
- else if (nodes_empty(*nodes))
+ if (nodes_empty(*nodes))
return -EINVAL; /* no allowed nodes */
- else
- pol->v.preferred_node = first_node(*nodes);
+ pol->v.preferred_node = first_node(*nodes);
return 0;
}
@@ -239,9 +236,11 @@ static int mpol_set_nodemask(struct mempolicy *pol,
cpuset_current_mems_allowed, node_states[N_MEMORY]);
VM_BUG_ON(!nodes);
- if (pol->mode == MPOL_PREFERRED && nodes_empty(*nodes))
- nodes = NULL; /* explicit local allocation */
- else {
+ if (pol->mode == MPOL_PREFERRED && nodes_empty(*nodes)) {
+ /* explicit local allocation */
+ pol->flags |= MPOL_F_LOCAL;
+ return 0;
+ } else {
if (pol->flags & MPOL_F_RELATIVE_NODES)
mpol_relative_nodemask(&nsc->mask2, nodes, &nsc->mask1);
else
@@ -254,10 +253,7 @@ static int mpol_set_nodemask(struct mempolicy *pol,
cpuset_current_mems_allowed;
}
- if (nodes)
- ret = mpol_ops[pol->mode].create(pol, &nsc->mask2);
- else
- ret = mpol_ops[pol->mode].create(pol, NULL);
+ ret = mpol_ops[pol->mode].create(pol, &nsc->mask2);
return ret;
}
Thanks,
Feng
next prev parent reply other threads:[~2021-04-19 8:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 3:39 [PATCH v4 00/13] Introduced multi-preference mempolicy Feng Tang
2021-03-17 3:39 ` [PATCH v4 01/13] mm/mempolicy: Add comment for missing LOCAL Feng Tang
2021-03-17 3:39 ` [PATCH v4 02/13] mm/mempolicy: convert single preferred_node to full nodemask Feng Tang
2021-04-14 12:17 ` Michal Hocko
2021-03-17 3:40 ` [PATCH v4 03/13] mm/mempolicy: Add MPOL_PREFERRED_MANY for multiple preferred nodes Feng Tang
2021-04-14 12:50 ` Michal Hocko
2021-04-20 7:16 ` Feng Tang
2021-05-13 7:23 ` Feng Tang
2021-05-13 7:25 ` [RFC PATCH 2/2] mempolicy: kill MPOL_F_LOCAL bit Feng Tang
2021-05-13 13:55 ` Andi Kleen
2021-03-17 3:40 ` [PATCH v4 04/13] mm/mempolicy: allow preferred code to take a nodemask Feng Tang
2021-04-14 12:55 ` Michal Hocko
2021-04-19 8:49 ` Feng Tang [this message]
2021-03-17 3:40 ` [PATCH v4 05/13] mm/mempolicy: refactor rebind code for PREFERRED_MANY Feng Tang
2021-04-14 12:57 ` Michal Hocko
2021-03-17 3:40 ` [PATCH v4 06/13] mm/mempolicy: kill v.preferred_nodes Feng Tang
2021-04-14 12:58 ` Michal Hocko
2021-03-17 3:40 ` [PATCH v4 07/13] mm/mempolicy: handle MPOL_PREFERRED_MANY like BIND Feng Tang
2021-04-14 13:01 ` Michal Hocko
2021-03-17 3:40 ` [PATCH v4 08/13] mm/mempolicy: Create a page allocator for policy Feng Tang
2021-04-14 13:08 ` Michal Hocko
2021-04-15 8:17 ` Feng Tang
2021-03-17 3:40 ` [PATCH v4 09/13] mm/mempolicy: Thread allocation for many preferred Feng Tang
2021-03-17 3:40 ` [PATCH v4 10/13] mm/mempolicy: VMA " Feng Tang
2021-04-14 13:14 ` Michal Hocko
2021-03-17 3:40 ` [PATCH v4 11/13] mm/mempolicy: huge-page " Feng Tang
2021-03-17 7:19 ` kernel test robot
2021-04-14 13:25 ` Michal Hocko
2021-04-15 7:41 ` Feng Tang
2021-03-17 3:40 ` [PATCH v4 12/13] mm/mempolicy: Advertise new MPOL_PREFERRED_MANY Feng Tang
2021-03-17 3:40 ` [PATCH v4 13/13] mem/mempolicy: unify mpol_new_preferred() and mpol_new_preferred_many() Feng Tang
2021-04-14 11:21 ` [PATCH v4 00/13] Introduced multi-preference mempolicy Michal Hocko
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