[Cluster-devel] [GFS2 PATCH] GFS2: Allocate reservation during write_begin if needed

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On 17/02/15 19:09, Bob Peterson wrote:
> ----- Original Message -----
>> Hi,
>>
>>
>> Since we set the allocation structure when the write call begins, and it
>> is not deallocated until there are no writers left with the file open,
>> how does this happen?
>>
>> Steve.
> Hi,
>
> In a normal write, the code goes through gfs2_page_mkwrite or
> gfs2_file_aio_write. In the failing scenario, it's going through
> sendfile. I suppose I could patch sendfile as an alternative, but
> the advantage here is that this patch will do it only if a block
> allocation is needed.
>
> Regards,
>
> Bob Peterson
> Red Hat File Systems

Ah, I see. In which case that code path should be patched. So it should 
be part of the splice code I think, since it should be done at the 
higher level, and not at the write_begin level, since that is too late. 
We should have a call to the reservation code too at that point, to 
ensure that we don't have fragmentation issues. So we need a wrapper for 
|iter_file_splice_write| along the lines of gfs2_file_write_iter I think,

Steve.

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