|| ||Chris Mason <chris.mason-AT-oracle.com>|
|| ||Akira Fujita <a-fujita-AT-rs.jp.nec.com>|
|| ||Re: [RFC][PATCH 0/3] ext4: online defrag (ver 1.0)|
|| ||Fri, 30 Jan 2009 15:15:18 -0500|
|| ||Theodore Tso <tytso-AT-mit.edu>, linux-ext4-AT-vger.kernel.org,
|| ||Article, Thread
On Fri, 2009-01-30 at 15:11 +0900, Akira Fujita wrote:
> I have rewritten ext4 online defrag patches based on the comments from Ted.
> In the new defrag, create donor inode in the user space instead of kernel space,
> and then allocate contiguous blocks to it with fallocate().
> In kernel space, exchange the blocks between target inode and donor inode,
> and then copy the file data of target inode to donor inode every 64MB.
> The EXT4_IOC_DEFRAG ioctl becomes simpler than the old one,
> so it may be useful for other purposes.
One thing you'll want to handle is swap files. The swap code uses the
bmap ioctl to make a mapping of extents in the files, and expects that
mapping not to change. So, defragging a swap file will lead to some
Btrfs is currently getting around this by dropping bmap support, so
swapfiles on btrfs won't work at all. A real long term solution is
For ext4 you should be able to just detect swapfile and disallow the
defrag on it.
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