Re: [Xen-devel] Xen 4.0.1 "xc_map_foreign_batch: mmap failed: Cannot allocate memory"

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 06.01.11 at 21:49, Charles Arnold wrote:
> >>> On 1/6/2011 at 10:14 AM, in message <4D25C782.5B74.0091.0@xxxxxxxxxx>, 
> >>> 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;
>>>     }
>> 
>> 
> 




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