[Ocfs2-devel] Why ocfs2 haven't implemented "steal" for local_alloc system files?

[Younger Liu <younger.liu@huawei.com>]

On 2013/8/1 15:20, Joel Becker wrote:
> Basically, there's so little in the cache that stealing would be too
> complex.  Really we just want to fall back to the global, and if that is
> empty, you're near enough ENOSPC that it doesn't much matter.
> 
> Joel
> 
Localalloc is a mount option. When mounting an ocfs2 volume, localalloc can
be set a larger size. For example, 2G or a larger number.

In a multi-nodes cluster, all nodes mount ocfs2 volume with localalloc=2048
for performance consideration, if a node claims space for a file, but there 
is no space in the local_alloc and global_bitmap. It would return ENOSPC.
However, other nodes may have lots of space which have been claimed 
in local_alloc, so ENOSPC cannot reflect the actual situation.

IMO, if there is no space both in the local_alloc and global_bitmap,
it should steal space from other nodes local_alloc.

Thx, 
Younger.

> On Wed, Jul 31, 2013 at 08:33:48PM -0700, Sunil Mushran wrote:
>> Because it makes no sense. Unlike inode/extent allocs, local_alloc is a
>> temporary cache. If you fail to allocate, you fallback to the global bitmap.
>>
>>
>> On Sat, Jul 27, 2013 at 3:27 AM, Younger Liu <younger.liu@huawei.com> wrote:
>>
>>> Hi,
>>>   While analyzing ocfs2 block allocation, I found:
>>>   When claiming space from inode_alloc (or extent_alloc) system files,
>>> if there is no enough space in inode_alloc (or extent_alloc) and
>>> global_bitmap, it could steal space from other slots.
>>>   But when claiming space from local_alloc system files, and no
>>> enough space in local_alloc and global_bitmap, it returns -ENOSPC.
>>>
>>>   Why ocfs2 haven't implemented "steal" for local_alloc system files?
>>>   Is there any some reasons?
>>>
>>>
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>>>
> 
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>