On Sat, Nov 01, 2008 at 08:54:30AM +1100, Dave Chinner wrote: > Effectively, yes. > > Currently we iterate inodes for data and "metadata" sync, and the > only other concept is writing superblocks. I think most filesystems > have more types of metadata than this, so it makes sense for sync to > work on abstracts sync as data and metadata rather than data, inodes > and superblocks... Yes, absolutely. And for those that have inodes as primary / only metadata besides superblock we can still provide a generic_sync_inodes helper that just takes a callback to apply to every inode. Which we probably want anyway as XFS is the only intree-filesystem that currently has a more efficient way to iterate inodes. > > And as we found out it's not just sync that gets it wrong, it's also > > fsync (which isn't part of the above picture as it's per-inode) that > > gets this utterly wrong, as well as all kinds of syncs, not just the > > unmount one. > > Async writeback (write_inode()) has the same problem as fsync - > writing the inode before waiting for data I/O to complete - which > means we've got to jump through hoops in the filesystem to avoid > blocking on inodes that can't be immediately flushed, and often we > end up writing the inode multiple times and having to issue log > forces whenw e shouldn't need to. Effectively we have to tell the > VFS to "try again later" the entire time data is being flushed > before we can write the inode and it's exceedingly inefficient..... Yes, that was the couple of sync functions I meant above as the whole inode writeback path is extremly convoluted - mostly due to the dirty data vs metadata mixup mess. -- 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
