On Tue 09-11-10 16:41:47, Ted Ts'o wrote: > On Tue, Nov 09, 2010 at 03:42:42PM +1100, Dave Chinner wrote: > > Implementation is up to the filesystem. However, XFS does (b) > > because: > > > > 1) it was extremely simple to implement (one of the > > advantages of having an exceedingly complex allocation > > interface to begin with :P) > > 2) conversion is atomic, fast and reliable > > 3) it is independent of the underlying storage; and > > 4) reads of unwritten extents operate at memory speed, > > not disk speed. > > Yeah, I was thinking that using a device-style TRIM might be better > since future attempts to write to it won't require a separate seek to > modify the extent tree. But yeah, there are a bunch of advantages of > simply mutating the extent tree. > > While we're on the subject of changes to fallocate, what do people > think of FALLOC_FL_EXPOSE_OLD_DATA, which requires either root > privileges or (if capabilities are in use) CAP_DAC_OVERRIDE && > CAP_MAC_OVERRIDE && CAP_SYS_ADMIN. This would allow a trusted process > to fallocate blocks with the extent already marked initialized. I've > had two requests for such functionality for ext4 already. > > (Take for example a trusted cluster filesystem backend that checks the > object checksum before returning any data to the user; and if the > check fails the cluster file system will try to use some other replica > stored on some other server.) Hum, could you elaborate a bit? I fail to see how above fallocate() flag could be used to help solving this problem... Just curious... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
