On Thu, Feb 04, 2010 at 10:30:06AM -0500, Christoph Hellwig wrote: > On Wed, Feb 03, 2010 at 05:44:24PM -0600, Ben Myers wrote: > > The following series is adds a 'wsync' export option to nfsd. It is intended > > to be used on XFS with the wsync mount option. When you already have a > > synchronous log there is no need to sync metadata separately. > > You don't need the xfs wsync option, as the existing write_inode calls > or your new fsync calls are doing the same as the wsync mount option, > just from a higher layer. Ok, I see that now. write_inode_now is basically a superset of what we need. The important thing is to force the log (which xfs_file_operations.xfs_file_fsync does do) but not to call xfs_super_operations.write_inode (via write_inode_now) which eventually gets into xfs_iflush and takes forever. We can take forever later-- when the log is full. ;) > The wsync option causes the log to be synchronously forced up to the > log sequence number of the commit for the metadata operation, that is > make all the operations affected by it synchronous. That's exactly > what we'll do using fsync (actually right now we force the whole log, > but I have a patch to optimize it to only force nuntil the last commit > lsn), and approqimately the same as we do using write_inode, just a > lot less efficiently. Rather than having X number of synchronous log transactions written separately as with wsync you have X number of log transactions written out together in one go by vfs_fsync (if datasync==0). That should be faster than wsync. > > Curious to hear if this is a reasonable thing to do. Suggestions > > welcome. > > I think it's reasonable. What might be even better it to have an > export operation call out into the filesystem so that we can force > wsync and not let nfsd deal with it at all. There is a fair chance > that the filesystem can do the sync more efficiently. Trond also suggested an export_operation and I think it's a good idea. I'll explore that and repost. Thanks, Ben -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
