[0/2] memrlimit improve error handling

[Balbir Singh]

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@iridium kamezawa]# cat /opt/cgroup/test/memrlimit.usage_in_bytes
71921664
[root@iridium kamezawa]# ulimit -s 3
[root@iridium kamezawa]# ls
Killed
[root@iridium kamezawa]# ls
Killed
[root@iridium kamezawa]# ls
Killed
[root@iridium kamezawa]# ls
Killed
[root@iridium kamezawa]# ls
Killed
[root@iridium kamezawa]# ulimit -s unlimited
[root@iridium kamezawa]# cat /opt/cgroup/test/memrlimit.usage_in_bytes
72368128
[root@iridium kamezawa]#

This patch adds better handling support to fix the reported problem.

Reported-By: kamezawa.hiroyu@xxxxxxxxxxxxxx

Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
---

 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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