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

[Xiao Yang]

Hi,

Adding Cyril to CC.  :-)

Thanks,
Xiao Yang

On 2018/01/16 17:11, Xiao Yang wrote:
> On 2018/01/15 23:58, Jan Stancek wrote:
>> ----- 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
> Hi Jan,
>
> Thanks for your detailed explanation.
>
> According to documented behavior of cgroups [1], it seems that only a 
> new cgroup
> hierarchy with the same options of the existing hierarchy can be 
> mounted sucessfully,
> and mount with different options will fail and return EBUSY as expected.
>
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/cgroup-v1/cgroups.txt
>
> Combinations of sucess:
> ----------------------------------------------------------------------------- 
>
> 1) # mkdir -p /tmp/1; mount -t cgroup -o memory,hugetlb none /tmp/1; 
> echo $?
>    0
>    # mkdir -p /tmp/2; mount -t cgroup -o memory,hugetlb none /tmp/2; 
> echo $?
>    0
> 2) # mkdir -p /tmp/1; mount -t cgroup -o memory none /tmp/1; echo $?
>    0
>    # mkdir -p /tmp/2; mount -t cgroup -o memory none /tmp/2; echo $?
>    0
> ----------------------------------------------------------------------------- 
>
>
> Combinations of failure:
> ----------------------------------------------------------------------------- 
>
> 3) # mkdir -p /tmp/1; mount -t cgroup -o memory,hugetlb none /tmp/1; 
> echo $?
>    0
>    # 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
>
> 4) # mkdir -p /tmp/1; mount -t cgroup -o memory none /tmp/1; echo $?
>    0
>    # mkdir -p /tmp/2; mount -t cgroup -o memory,hugetlb none /tmp/2; 
> echo $?
>      mount: none is already mounted or /tmp/2 busy
>             none is already mounted on /tmp/1
>    32
> ----------------------------------------------------------------------------- 
>
>
> I am not sure how to fix all errors.
>
>>>   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)
> I think we can hold it until LTP is released.
>
> Thanks,
> Xiao Yang.
>
>> 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;
>>>>>
>>>>>
>>>> .
>>>>
>>>
>>>
>>>
>>
>> .
>>
>
>
>
>