Re: [RFC][PATCH] ChunkFS: fs fission for faster fsck

Jeff Dike
2007-04-26T16:11:38Z

On Thu, Apr 26, 2007 at 10:53:16AM -0500, Amit Gud wrote:
> Jeff Dike wrote:
> >How about this case:
> >
> > Growing file starts in chunk A.
> > Overflows into chunk B.
> > Delete file in chunk A.
> > Growing file overflows chunk B and spots new free space in
> >chunk A (and nothing anywhere else)
> > Overflows into chunk A
> > Delete file in chunk B.
> > Overflow into chunk B again.
> >
> >Maybe this is not realistic, but in the absence of a mechanism to pull
> >data back from an overflow chunk, it seems at least a theoretical
> >possibility that there could be > 1 continuation inodes per file per
> >chunk.
> >
>
> Preventive measures are taken to limit only one continuation inode per
> file per chunk. This can be done easily in the chunk allocation
> algorithm for disk space. Although I'm not quite sure what you mean by
> "Delete file in chunk A". If you are referring to same file thats
> growing, then deletion is not possible, because individual parts of any
> file in any chunk cannot be deleted.

No, I'm referring to a different file. The scenario is that you have
a growing file in a nearly full disk with files being deleted (and
thus space being freed) such that allocations for the growing file
bounce back and forth between chunks.

Jeff

--
Work email - jdike at linux dot intel dot com