On Tue, Oct 24, 2006 at 12:14:33AM -0400, Jeff Garzik wrote: > On Mon, Oct 23, 2006 at 06:31:40PM +0400, Alex Tomas wrote: > > 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? > > The kernel doesn't have enough knowledge to know whether or not the > defragger prefers one blkdev location over another. > > When you are trying to consolidate blocks, you must specify the > destination as well as source blocks. > > Certainly, to prevent corruption and other nastiness, you must fail if > the destination isn't available... That's the wrong way to look at it. if you want the userspace process to specify a location, then you should preallocate it first before doing anything else. There is no need to clutter a simple data mover interface with all sorts of unnecessary error handling. Once you've separated the destination allocation from the data mover, the mover is basically a splice copy from source to destination, an fsync and then an atomic swap blocks/extents operation. Most of this code is generic, and a per-fs swap-extents vector could be easily provided for the one bit that is not.... The allocation interface, OTOH, is anything but simple and is really a filesystem specific interface. Seems logical to me to separate the two. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - 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
