On Tue, 26 February 2008 15:28:10 +0000, Jamie Lokier wrote: > > > One interesting aspect of this comes with COW filesystems like btrfs or > > logfs. Writing out data pages is not sufficient, because those will get > > lost unless their referencing metadata is written as well. So either we > > have to call fsync for those filesystems or add another callback and let > > filesystems override the default implementation. > > Doesn't the ->fsync callback get called in the sys_fdatasync() case, > with appropriate arguments? My paragraph above was aimed at the sync_file_range() case. fsync and fdatasync do the right thing within the limitations you brought up in this thread. sync_file_range() without further changes will only write data pages, not the metadata required to actually access those data pages. This works just fine for non-COW filesystems, which covers all currently merged ones. With COW filesystems it is currently impossible to do sync_file_range() properly. The problem is orthogonal to your's, I just brought it up since you were already mentioning sync_file_range(). Jörn -- Joern's library part 10: http://blogs.msdn.com/David_Gristwood/archive/2004/06/24/164849.aspx - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
