Question : memrlimit cgroup's task_move (2.6.26-rc5-mm3)
Balbir Singh
balbir at linux.vnet.ibm.com
Thu Jun 19 09:41:28 PDT 2008
* KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com> [2008-06-19 19:22:27]:
> On Thu, 19 Jun 2008 12:24:29 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com> wrote:
>
> > On Thu, 19 Jun 2008 08:43:43 +0530
> > Balbir Singh <balbir at linux.vnet.ibm.com> wrote:
> >
> > >
> > > > I think the charge of the new group goes to minus. right ?
> > > > (and old group's charge never goes down.)
> > > > I don't think this is "no problem".
> > > >
> > > > What kind of patch is necessary to fix this ?
> > > > task_attach() should be able to fail in future ?
> > > >
> > > > I'm sorry if I misunderstand something or this is already in TODO list.
> > > >
> > >
> > > It's already on the TODO list. Thanks for keeping me reminded about it.
> > >
> > Okay, I'm looking foward to see how can_attach and roll-back(if necessary)
> > is implemnted.
> > As you know, I'm interested in how to handle failure of task move.
> >
> One more thing...
> Now, charge is done at
>
> - vm is inserted (special case?)
> - vm is expanded (mmap is called, stack growth...)
>
> And uncharge is done at
> - vm is removed (success of munmap)
> - exit_mm is called (exit of process)
>
> But it seems charging at may_expand_vm() is not good.
> The mmap can fail after may_expand_vm() because of various reason,
> but charge is already done at may_expand_vm()....and no roll-back.
>
Hi, Kamezawa-San,
The patch I have below addresses the issue. FYI: I do see some
variation in memrlimit.usage_in_bytes after running ls, but it's not
that much. I verified that the patch behaves correctly, by doing
a cat of memrlimit.usage_in_bytes from another shell (not associated
with test group) and then compared that value to /proc/$$/statm
($$ being the pid of the task belonging to the test group).
Could you please review/test the patch below? If it works OK, I'll
request Andrew to pick it up.
Description
-----------
memrlimit cgroup does not handle error cases after may_expand_vm(). This
BUG was reported by Kamezawa, with the test case below to reproduce it
[root at iridium kamezawa]# cat /opt/cgroup/test/memrlimit.usage_in_bytes
71921664
[root at iridium kamezawa]# ulimit -s 3
[root at iridium kamezawa]# ls
Killed
[root at iridium kamezawa]# ls
Killed
[root at iridium kamezawa]# ls
Killed
[root at iridium kamezawa]# ls
Killed
[root at iridium kamezawa]# ls
Killed
[root at iridium kamezawa]# ulimit -s unlimited
[root at iridium kamezawa]# cat /opt/cgroup/test/memrlimit.usage_in_bytes
72368128
[root at iridium kamezawa]#
This patch adds better handling support to fix the reported problem.
Reported-By: kamezawa.hiroyu at jp.fujitsu.com
Signed-off-by: Balbir Singh <balbir at linux.vnet.ibm.com>
---
mm/mmap.c | 36 +++++++++++++++++++++++++-----------
mm/mremap.c | 6 ++++++
2 files changed, 31 insertions(+), 11 deletions(-)
diff -puN mm/mmap.c~memrlimit-cgroup-add-better-error-handling mm/mmap.c
--- linux-2.6.26-rc5/mm/mmap.c~memrlimit-cgroup-add-better-error-handling 2008-06-19 21:12:46.000000000 +0530
+++ linux-2.6.26-rc5-balbir/mm/mmap.c 2008-06-19 21:39:45.000000000 +0530
@@ -1123,7 +1123,7 @@ munmap_back:
*/
charged = len >> PAGE_SHIFT;
if (security_vm_enough_memory(charged))
- return -ENOMEM;
+ goto undo_charge;
vm_flags |= VM_ACCOUNT;
}
}
@@ -1245,6 +1245,8 @@ free_vma:
unacct_error:
if (charged)
vm_unacct_memory(charged);
+undo_charge:
+ memrlimit_cgroup_uncharge_as(mm, len >> PAGE_SHIFT);
return error;
}
@@ -1540,14 +1542,15 @@ static int acct_stack_growth(struct vm_a
struct mm_struct *mm = vma->vm_mm;
struct rlimit *rlim = current->signal->rlim;
unsigned long new_start;
+ int ret = -ENOMEM;
/* address space limit tests */
if (!may_expand_vm(mm, grow))
- return -ENOMEM;
+ goto out;
/* Stack limit test */
if (size > rlim[RLIMIT_STACK].rlim_cur)
- return -ENOMEM;
+ goto undo_charge;
/* mlock limit tests */
if (vma->vm_flags & VM_LOCKED) {
@@ -1556,21 +1559,23 @@ static int acct_stack_growth(struct vm_a
locked = mm->locked_vm + grow;
limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
if (locked > limit && !capable(CAP_IPC_LOCK))
- return -ENOMEM;
+ goto undo_charge;
}
/* Check to ensure the stack will not grow into a hugetlb-only region */
new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
vma->vm_end - size;
- if (is_hugepage_only_range(vma->vm_mm, new_start, size))
- return -EFAULT;
+ if (is_hugepage_only_range(vma->vm_mm, new_start, size)) {
+ ret = -EFAULT;
+ goto undo_charge;
+ }
/*
* Overcommit.. This must be the final test, as it will
* update security statistics.
*/
if (security_vm_enough_memory(grow))
- return -ENOMEM;
+ goto undo_charge;
/* Ok, everything looks good - let it rip */
mm->total_vm += grow;
@@ -1578,6 +1583,11 @@ static int acct_stack_growth(struct vm_a
mm->locked_vm += grow;
vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
return 0;
+undo_charge:
+ /* Undo memrlimit charge */
+ memrlimit_cgroup_uncharge_as(mm, grow);
+out:
+ return ret;
}
#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
@@ -1982,6 +1992,7 @@ unsigned long do_brk(unsigned long addr,
struct rb_node ** rb_link, * rb_parent;
pgoff_t pgoff = addr >> PAGE_SHIFT;
int error;
+ int ret = -ENOMEM;
len = PAGE_ALIGN(len);
if (!len)
@@ -2035,13 +2046,13 @@ unsigned long do_brk(unsigned long addr,
/* Check against address space limits *after* clearing old maps... */
if (!may_expand_vm(mm, len >> PAGE_SHIFT))
- return -ENOMEM;
+ return ret;
if (mm->map_count > sysctl_max_map_count)
- return -ENOMEM;
+ goto undo_charge;
if (security_vm_enough_memory(len >> PAGE_SHIFT))
- return -ENOMEM;
+ goto undo_charge;
/* Can we just expand an old private anonymous mapping? */
vma = vma_merge(mm, prev, addr, addr + len, flags,
@@ -2055,7 +2066,7 @@ unsigned long do_brk(unsigned long addr,
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (!vma) {
vm_unacct_memory(len >> PAGE_SHIFT);
- return -ENOMEM;
+ goto undo_charge;
}
vma->vm_mm = mm;
@@ -2073,6 +2084,9 @@ out:
mm->locked_vm += (len >> PAGE_SHIFT) - nr_pages;
}
return addr;
+undo_charge:
+ memrlimit_cgroup_uncharge_as(mm, len >> PAGE_SHIFT);
+ return ret;
}
EXPORT_SYMBOL(do_brk);
diff -puN mm/mremap.c~memrlimit-cgroup-add-better-error-handling mm/mremap.c
--- linux-2.6.26-rc5/mm/mremap.c~memrlimit-cgroup-add-better-error-handling 2008-06-19 21:12:46.000000000 +0530
+++ linux-2.6.26-rc5-balbir/mm/mremap.c 2008-06-19 22:00:02.000000000 +0530
@@ -18,6 +18,7 @@
#include <linux/highmem.h>
#include <linux/security.h>
#include <linux/syscalls.h>
+#include <linux/memrlimitcgroup.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
@@ -256,6 +257,7 @@ unsigned long do_mremap(unsigned long ad
struct vm_area_struct *vma;
unsigned long ret = -EINVAL;
unsigned long charged = 0;
+ int vm_expanded = 0;
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
goto out;
@@ -349,6 +351,7 @@ unsigned long do_mremap(unsigned long ad
goto out;
}
+ vm_expanded = 1;
if (vma->vm_flags & VM_ACCOUNT) {
charged = (new_len - old_len) >> PAGE_SHIFT;
if (security_vm_enough_memory(charged))
@@ -411,6 +414,9 @@ out:
if (ret & ~PAGE_MASK)
vm_unacct_memory(charged);
out_nc:
+ if (vm_expanded)
+ memrlimit_cgroup_uncharge_as(mm,
+ (new_len - old_len) >> PAGE_SHIFT);
return ret;
}
_
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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