Hi Chris, Chris Mason wrote: > On Fri, 2009-01-30 at 15:11 +0900, Akira Fujita wrote: >> Hi, >> >> 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 > serious problems. > > 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 > required ;) > > For ext4 you should be able to just detect swapfile and disallow the > defrag on it. > Thank you for teaching. ;) I'll add the swapfile checks to command and kernel. If target file is swapfile, ext4 online defrag returns an error without doing defrag in the next version. Regards, Akira Fujita -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
