Re: [LTP] [PATCH] Fix short of nodemask array.

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Zhouping Liu" <zliu@redhat.com>
> To: "gmail" <lans.zhang2008@gmail.com>
> Cc: ltp-list@lists.sourceforge.net, "Wanlong Gao" <gaowanlong@cn.fujitsu.com>, "Jan Stancek" <jstancek@redhat.com>
> Sent: Tuesday, 16 April, 2013 6:34:53 AM
> Subject: Re: [LTP] [PATCH]  Fix short of nodemask array.
> 
> Hi Lans,
> 
> ----- Original Message -----
> > From: "gmail" <lans.zhang2008@gmail.com>
> > To: ltp-list@lists.sourceforge.net
> > Sent: Monday, March 4, 2013 12:49:45 PM
> > Subject: [LTP] [PATCH]  Fix short of nodemask array.
> > 
> > In kernel, when the user specified more nodes, e.g, 512 nodes, than
> > supported, e.g, 4 nodes, just check if the non supported part is all
> > zero. If user space just specified the nodemask array with only one
> > element, which makes the check in kernel actually become invalid.
> 
> I think the comments here is not clear, you should explain more details
> about the 'one element' or the reason why the checking in kernel will
> be invalid.

I think what it says is that we are overrunning "nmask", whose length is
shorter than MAXNODES.

> 
> > In addition, some test cases in current implement doesn't consider
> > if a node number is greater than sizeof(unsigned long) * 8 - 1.
> 
> yes, you are right, we don't care the system which has more than 512 numa
> nodes.
> and the current code only support 64 numa nodes, only one unsigned long node
> mask.
> 
> I checked kernel code in RHEL6, CONFIG_NODES_SHIFT=9, so 512 is the biggest
> value to support in RHEL6 for x86_64, and I didn't meet any large NUMA system
> which have 512+ numa nodes so far.
> 
> > 
> > Signed-off-by: Lans Zhang <lans.zhang2008@gmail.com>
> > ---
> >   testcases/kernel/mem/cpuset/cpuset01.c |    6 +++---
> >   testcases/kernel/mem/ksm/ksm02.c       |    6 +++---
> >   testcases/kernel/mem/ksm/ksm04.c       |    6 +++---
> >   testcases/kernel/mem/lib/mem.c         |    6 +++---
> >   4 files changed, 12 insertions(+), 12 deletions(-)
> > 
> > diff --git a/testcases/kernel/mem/cpuset/cpuset01.c
> > b/testcases/kernel/mem/cpuset/cpuset01.c
> > index b473e45..e459306 100644
> > --- a/testcases/kernel/mem/cpuset/cpuset01.c
> > +++ b/testcases/kernel/mem/cpuset/cpuset01.c
> > @@ -93,7 +93,7 @@ static void testcpuset(void)
> >   {
> >   	int lc;
> >   	int child, i, status;
> > -	unsigned long nmask = 0;
> > +	unsigned long nmask[MAXNODES / (8*sizeof(unsigned long))] = { 0 };
> >   	char mems[BUFSIZ], buf[BUFSIZ];
> > 
> >   	read_cpuset_files(CPATH, "cpus", buf);
> > @@ -108,8 +108,8 @@ static void testcpuset(void)
> >   		tst_brkm(TBROK | TERRNO, cleanup, "fork");
> >   	case 0:
> >   		for (i = 0; i < nnodes; i++)
> > -			nmask += 1 << nodes[i];
> > -		if (set_mempolicy(MPOL_BIND, &nmask, MAXNODES) == -1)
> > +			nmask[i / (8*sizeof(unsigned long))] |= 1 << (i % (8*sizeof(unsigned
> > long)));
> > +		if (set_mempolicy(MPOL_BIND, nmask, MAXNODES) == -1)
> >   			tst_brkm(TBROK | TERRNO, cleanup, "set_mempolicy");
> >   		exit(mem_hog_cpuset(ncpus > 1 ? ncpus : 1));
> >   	}
> > diff --git a/testcases/kernel/mem/ksm/ksm02.c
> > b/testcases/kernel/mem/ksm/ksm02.c
> > index be9ff96..9d2d142 100644
> > --- a/testcases/kernel/mem/ksm/ksm02.c
> > +++ b/testcases/kernel/mem/ksm/ksm02.c
> > @@ -87,7 +87,7 @@ int main(int argc, char *argv[])
> >   	int lc;
> >   	char *msg;
> >   	int size = 128, num = 3, unit = 1;
> > -	unsigned long nmask = 0;
> > +	unsigned long nmask[MAXNODES / (8*sizeof(unsigned long))] = { 0 };
> >   	unsigned int node;
> > 
> >   	msg = parse_opts(argc, argv, ksm_options, ksm_usage);
> > @@ -95,7 +95,7 @@ int main(int argc, char *argv[])
> >   		tst_brkm(TBROK, NULL, "OPTION PARSING ERROR - %s", msg);
> > 
> >   	node = get_a_numa_node(tst_exit);
> > -	nmask = 1 << node;
> > +	nmask[node / (8*sizeof(unsigned long))] = 1 << (node % (8*sizeof(unsigned
> > long)));
> 
> I found '1 << (node % (8*sizeof(unsigned long)))' is used frequently, I
> suggest we
> can create a macro, such as:
> # define GET_NODE_MASK(nid) 1 << (nid % (8*sizeof(unsigned long)))

I agree, also 'nmask[i / (8*sizeof(unsigned long))]' is there often.
How about something like:

#define bitsperlong (8 * sizeof(unsigned long))
void set_bit(unsigned long *b, unsigned int n, unsigned int v)
{
        if (v)
                b[n / bitsperlong] |= 1UL << (n % bitsperlong);
        else
                b[n / bitsperlong] &= ~(1UL << (n % bitsperlong));
}
set_bit(nmask, node, 1);

Regards,
Jan

> 
> also please update the patch, as there's some updates before your patch in
> lib/mem.c,
> which makes some conflict with the latest tree.
> 
> Thanks,
> Zhouping
> 
> > 
> >   	setup();
> > 
> > @@ -103,7 +103,7 @@ int main(int argc, char *argv[])
> >   		Tst_count = 0;
> >   		check_ksm_options(&size, &num, &unit);
> > 
> > -		if (set_mempolicy(MPOL_BIND, &nmask, MAXNODES) == -1) {
> > +		if (set_mempolicy(MPOL_BIND, nmask, MAXNODES) == -1) {
> >   			if (errno != ENOSYS)
> >   				tst_brkm(TBROK | TERRNO, cleanup,
> >   					 "set_mempolicy");
> > diff --git a/testcases/kernel/mem/ksm/ksm04.c
> > b/testcases/kernel/mem/ksm/ksm04.c
> > index e4aa417..7829afd 100644
> > --- a/testcases/kernel/mem/ksm/ksm04.c
> > +++ b/testcases/kernel/mem/ksm/ksm04.c
> > @@ -87,7 +87,7 @@ int main(int argc, char *argv[])
> >   	int lc;
> >   	char *msg;
> >   	int size = 128, num = 3, unit = 1;
> > -	unsigned long nmask = 0;
> > +	unsigned long nmask[MAXNODES / (8*sizeof(unsigned long))] = { 0 };
> >   	unsigned int node;
> > 
> >   	msg = parse_opts(argc, argv, ksm_options, ksm_usage);
> > @@ -95,7 +95,7 @@ int main(int argc, char *argv[])
> >   		tst_brkm(TBROK, NULL, "OPTION PARSING ERROR - %s", msg);
> > 
> >   	node = get_a_numa_node(tst_exit);
> > -	nmask = 1 << node;
> > +	nmask[node / (8*sizeof(unsigned long))] = 1 << (node % (8*sizeof(unsigned
> > long)));
> > 
> >   	setup();
> > 
> > @@ -105,7 +105,7 @@ int main(int argc, char *argv[])
> > 
> >   		write_memcg();
> > 
> > -		if (set_mempolicy(MPOL_BIND, &nmask, MAXNODES) == -1) {
> > +		if (set_mempolicy(MPOL_BIND, nmask, MAXNODES) == -1) {
> >   			if (errno != ENOSYS)
> >   				tst_brkm(TBROK | TERRNO, cleanup,
> >   					 "set_mempolicy");
> > diff --git a/testcases/kernel/mem/lib/mem.c
> > b/testcases/kernel/mem/lib/mem.c
> > index f095fe1..abe29fd 100644
> > --- a/testcases/kernel/mem/lib/mem.c
> > +++ b/testcases/kernel/mem/lib/mem.c
> > @@ -66,12 +66,12 @@ void oom(int testcase, int mempolicy, int lite)
> >   	int status;
> >   #if HAVE_NUMA_H && HAVE_LINUX_MEMPOLICY_H && HAVE_NUMAIF_H \
> >   	&& HAVE_MPOL_CONSTANTS
> > -	unsigned long nmask = 0;
> > +	unsigned long nmask[MAXNODES / (8*sizeof(unsigned long))] = { 0 };
> >   	unsigned int node;
> > 
> >   	if (mempolicy)
> >   		node = get_a_numa_node(cleanup);
> > -	nmask += 1 << node;
> > +	nmask[node / (8*sizeof(unsigned long))] = 1 << (node % (8*sizeof(unsigned
> > long)));
> >   #endif
> > 
> >   	switch (pid = fork()) {
> > @@ -81,7 +81,7 @@ void oom(int testcase, int mempolicy, int lite)
> >   #if HAVE_NUMA_H && HAVE_LINUX_MEMPOLICY_H && HAVE_NUMAIF_H \
> >   	&& HAVE_MPOL_CONSTANTS
> >   		if (mempolicy)
> > -			if (set_mempolicy(MPOL_BIND, &nmask, MAXNODES) == -1)
> > +			if (set_mempolicy(MPOL_BIND, nmask, MAXNODES) == -1)
> >   				tst_brkm(TBROK | TERRNO, cleanup,
> >   					 "set_mempolicy");
> >   #endif
> > --
> > 1.7.8.110.g4cb5d
> > 
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> > 
> 
> --
> Thanks,
> Zhouping
> 

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