Re: Xen 4.0.1 "xc_map_foreign_batch: mmap failed: Cannot allocate memory"

["Jan Beulich" <JBeulich@novell.com>]

>>> On 06.01.11 at 21:49, Charles Arnold wrote:
> >>> On 1/6/2011 at 10:14 AM, in message <4D25C782.5B74.0091.0@novell.com>, Charles Arnold wrote: 
> Attached is the messages file with the printk output.

Hmm, a failure due to may_expand_vm() is really odd. Something
must be explicitly setting a non-infinite RLIMIT_AS on qemu-dm (or
one of its parents), as the default is "infinite" (as reaching "infinity"
- being ~0UL - is simply impossible, and unduly large lengths should
be caught by get_unmapped_area() already).

/proc/<pid>/limits would at least tell us what the limit is.

And certainly qemu-dm needs to be prepared to have a
non-infinite address space limit set on it.

Jan - Charles
> 
>>> ---
>>> 
>>> 
>>> 
>>> diff --git a/mm/mmap.c b/mm/mmap.c
>>> index b179abb..3f65277 100644
>>> --- a/mm/mmap.c
>>> +++ b/mm/mmap.c
>>> @@ -991,16 +991,20 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned 
> 
>> 
>>> long addr,
>>>  
>>>  	/* Careful about overflows.. */
>>>  	len = PAGE_ALIGN(len);
>>> -	if (!len)
>>> +	if (!len) {
>>> +		printk("DEBUG PAGE_ALIGN ENOMEM\n");
>>>  		return -ENOMEM;
>>> +	}
>>>  
>>>  	/* offset overflow? */
>>>  	if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
>>>                 return -EOVERFLOW;
>>>  
>>>  	/* Too many mappings? */
>>> -	if (mm->map_count > sysctl_max_map_count)
>>> +	if (mm->map_count > sysctl_max_map_count) {
>>> +		printk("DEBUG too many mappings ENOMEM\n");
>>>  		return -ENOMEM;
>>> +	}
>>>  
>>>  	/* Obtain the address to map to. we verify (or select) it and ensure
>>>  	 * that it represents a valid section of the address space.
>>> @@ -1231,14 +1235,18 @@ unsigned long mmap_region(struct file *file, unsigned 
> 
>> 
>>> long addr,
>>>  munmap_back:
>>>  	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
>>>  	if (vma && vma->vm_start < addr + len) {
>>> -		if (do_munmap(mm, addr, len))
>>> +		if (do_munmap(mm, addr, len)) {
>>> +			printk("DEBUG find_vma_prepare ENOMEM\n");
>>>  			return -ENOMEM;
>>> +		}
>>>  		goto munmap_back;
>>>  	}
>>>  
>>>  	/* Check against address space limit. */
>>> -	if (!may_expand_vm(mm, len >> PAGE_SHIFT))
>>> +	if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
>>> +		printk("DEBUG may_expand_vm ENOMEM\n");
>>>  		return -ENOMEM;
>>> +	}
>>>  
>>>  	/*
>>>  	 * Set 'VM_NORESERVE' if we should not account for the
>>> @@ -1259,8 +1267,10 @@ munmap_back:
>>>  	 */
>>>  	if (accountable_mapping(file, vm_flags)) {
>>>  		charged = len >> PAGE_SHIFT;
>>> -		if (security_vm_enough_memory(charged))
>>> +		if (security_vm_enough_memory(charged)) {
>>> +			printk("DEBUG accountable_mapping ENOMEM\n");
>>>  			return -ENOMEM;
>>> +		}
>>>  		vm_flags |= VM_ACCOUNT;
>>>  	}
>>>  
>>> @@ -1278,6 +1288,7 @@ munmap_back:
>>>  	 */
>>>  	vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
>>>  	if (!vma) {
>>> +		printk("DEBUG kmem_cache_zalloc ENOMEM\n");
>>>  		error = -ENOMEM;
>>>  		goto unacct_error;
>>>  	}
>> 
>> 
>