On Jan 16, 2007 21:03 +0900, sho@xxxxxxxxxxxxxx wrote:
> 1. Add new ioctl(EXT4_IOC_DEFRAG) which returns the first physical
> block number of the specified file. With this ioctl, a command
> gets the specified directory's.
Maybe I don't understand, but how is this different from the long-time
FIBMAP ioctl?
> 2. The new entry "goal" is added on ext4_ext_defrag_data structure
> which is passed to existing ioctl(EXT4_IOC_DEFRAG)
> as the argument. The kernel starts searching the free blocks
> from "goal". The command passes the physical block number
> gotten in the above step(1) to the ioctl.
>
> struct ext4_ext_defrag_data {
> loff_t start_offset; /* start offset to defrag in byte */
> loff_t defrag_size; /* size of defrag in bytes */
> ext4_fsblk_t goal; /* block offset for allocation */
> };
Two things of note:
- presumably the start_offset and defrag_size should be multiples of the
filesystem blocksize? If they are not, is it an error or are they
adjusted to cover whole blocks?
- in previous defrag discussions (i.e. XFS defrag), it was desirable to
allow specifying different types of goals (e.g. hard, soft, kernel picks).
We may as well have a structure that allows these to be specified, instead
of having to change the interface afterward.
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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