Alex Tomas wrote:
Theodore Tso (TT) writes:
TT> On Mon, Oct 23, 2006 at 02:27:10PM +0200, Jan Kara wrote:
>> Hello,
>>
>> I've written a simple patch implementing ext3 ioctl for file
>> relocation. Basically you call ioctl on a file, give it list of blocks
>> and it relocates the file into given blocks (provided they are still
>> free). The idea is to use it as a kernel part of ext3 online
>> defragmenter (or generally disk access optimizer).
isn't that a kernel responsbility to find/allocate target blocks?
wouldn't it better to specify desirable target group and minimal
acceptable chunk of free blocks?
XFS does this by allocating new blocks for a temporary file (initiated from
userspace, implemented in kernelspace of course), then just checks to see if the
result is better than what we had before; if so, then swap the storage space &
throw away the temporary file (which now has the original, more-fragmented file
blocks).
see xfs_swapext() in xfs_dfrag.c for the extent swapping part of this.
You probably want to avoid the page cache in all of this too, doing O_DIRECT IO
if possible, I don't think there's any reason to churn the page cache while the
defragmenter runs over a filesystem?
-Eric
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