On Sun, Feb 25, 2018 at 12:40:47PM +0100, Gionatan Danti wrote: > Il 25-02-2018 03:47 Dave Chinner ha scritto: > > > >Yes, you have to freeze the filesystem to get a crash-consistent > >snapshot of the filesystem. > > > > > >You will end up with garbage. > > Ok. Bonus question: am I right thinking this is due to the CoW copy > not being atomic (ie: the various extents being in different state > until the copy is finished)? This isn't a copy on write issue. This is an issue of the state of the file and the I/O stack above it at the time the data extents are shared. There is I/O inflight, and so there's no guarantee that what is in the extents being shared is consistent. Freezing the filesystem stops IO in flight, so the extents can be shared while the filesystem knows it has consistent state on stable storage. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
