[LTP] [PATCH v2] syscalls/madvise09.c: Use custom mount point instead of /sys/fs/cgroup/memory

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> On 2018/01/15 16:06, Jan Stancek wrote:
> >
> > ----- Original Message -----
> >> Hi Jan,
> >>
> >> Could you help me review this patch.
> > Hi,
> >
> > I think it would be better to use existing mount, if it's already mounted.
> > umount may fail with -EBUSY if the subsystem is already part of existing
> > hierarchy.
> Hi Jan,
> 
> 1) I want to run madvise09 on as many distros supporting memcg as possible.
> 
> 2) The custom mount point is just created and mounted for running
> madvise09, and will be
>      released after finishing madvise09, so i think it doesn't affect
> existing hierarchy.

Here's example:

This is state of the system prior to madvise09:
# mkdir -p /tmp/1; mount -t cgroup -o memory,hugetlb none /tmp/1; echo $?
0

And now you run madvise09, that tries to mount "memory" cgroup, which is going to fail:
# mkdir -p /tmp/2; mount -t cgroup -o memory none /tmp/2; echo $?
mount: none is already mounted or /tmp/2 busy
       none is already mounted on /tmp/1
32

>  Additionally,
>      i use custom mount point according to some tests(oom03, oom05,
> cpuset01, etc.) on LTP.

OK, so my example, though possible is likely not very common.

We are close to next LTP release, can this wait or is this a regression
that should be addressed before release? (Adding Cyril to CC)

Regards,
Jan

> 
> Thanks,
> Xiao Yang
> > Regards,
> > Jan
> >
> >> Thanks,
> >> Xiao Yang
> >> On 2018/01/04 10:43, xiao yang wrote:
> >>> 1) on some distros(e.g. RHEL6), memory cgroup was supported and
> >>>     mounted on /cgroup/memory by default, but the test was skipped
> >>>     if /sys/fs/cgroup/memory did not exist.
> >>>
> >>> 2) We got the following error if memory cgroup wasn't mounted
> >>>     on /sys/fs/cgroup/memory:
> >>>     ------------------------------------------------------------
> >>>     safe_macros.c:169: BROK: madvise09.c:175:
> >>>     mkdir(/sys/fs/cgroup/memory/ltp_madvise09_16386/,0777) failed: EROFS
> >>>     ------------------------------------------------------------
> >>>
> >>> We use custom mount point and mount memory cgroup on it manually
> >>> to fix these issues.
> >>>
> >>> Signed-off-by: xiao yang<yangx.jy@cn.fujitsu.com>
> >>> ---
> >>>   testcases/kernel/syscalls/madvise/madvise09.c | 26
> >>>   ++++++++++++++++++++++----
> >>>   1 file changed, 22 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/testcases/kernel/syscalls/madvise/madvise09.c
> >>> b/testcases/kernel/syscalls/madvise/madvise09.c
> >>> index f744405..25cf81f 100644
> >>> --- a/testcases/kernel/syscalls/madvise/madvise09.c
> >>> +++ b/testcases/kernel/syscalls/madvise/madvise09.c
> >>> @@ -53,12 +53,14 @@
> >>>   #include<errno.h>
> >>>   #include<stdio.h>
> >>>   #include<ctype.h>
> >>> +#include<sys/mount.h>
> >>>
> >>>   #include "tst_test.h"
> >>>   #include "lapi/mmap.h"
> >>>
> >>> -#define MEMCG_PATH "/sys/fs/cgroup/memory/"
> >>> +#define MEMCG_PATH "/dev/memcg_madvise09/"
> >>>
> >>> +static int memcg_mounted;
> >>>   static char cgroup_path[PATH_MAX];
> >>>   static char tasks_path[PATH_MAX];
> >>>   static char limit_in_bytes_path[PATH_MAX];
> >>> @@ -277,6 +279,15 @@ static void cleanup(void)
> >>>   {
> >>>   	if (cgroup_path[0]&&  !access(cgroup_path, F_OK))
> >>>   		rmdir(cgroup_path);
> >>> +
> >>> +	if (memcg_mounted) {
> >>> +		tst_res(TINFO, "Umount memory cgroup after testing");
> >>> +		SAFE_UMOUNT(MEMCG_PATH);
> >>> +		memcg_mounted = 0;
> >>> +	}
> >>> +
> >>> +	if (!access(MEMCG_PATH, F_OK)&&  rmdir(MEMCG_PATH))
> >>> +		tst_res(TWARN | TERRNO, "Rmdir %s failed", MEMCG_PATH);
> >>>   }
> >>>
> >>>   static void run(void)
> >>> @@ -316,10 +327,17 @@ static void setup(void)
> >>>   {
> >>>   	long int swap_total;
> >>>
> >>> -	if (access(MEMCG_PATH, F_OK)) {
> >>> -		tst_brk(TCONF, "'" MEMCG_PATH
> >>> -			"' not present, CONFIG_MEMCG missing?");
> >>> +	SAFE_MKDIR(MEMCG_PATH, 0777);
> >>> +
> >>> +	tst_res(TINFO, "Mount memory cgroup on %s", MEMCG_PATH);
> >>> +	if (mount("memcg", MEMCG_PATH, "cgroup", 0, "memory") == -1) {
> >>> +		if (errno == ENODEV) {
> >>> +			tst_brk(TCONF,
> >>> +				 "Memory cgroup was not configured in kernel");
> >>> +		}
> >>> +		tst_brk(TBROK | TERRNO, "Failed to mount memory cgroup");
> >>>   	}
> >>> +	memcg_mounted = 1;
> >>>
> >>>   	if (!access(MEMCG_PATH "memory.memsw.limit_in_bytes", F_OK))
> >>>   		swap_accounting_enabled = 1;
> >>
> >>
> >>
> >
> > .
> >
> 
> 
> 
>