On Wed, 2011-03-23 at 17:00 -0400, Christoph Hellwig wrote: > > @@ -326,6 +326,9 @@ nfs_file_fsync(struct file *file, int datasync) > > ret = xchg(&ctx->error, 0); > > if (!ret && status < 0) > > ret = status; > > + if (!ret && !datasync) > > + /* application has asked for meta-data sync */ > > + ret = pnfs_layoutcommit_inode(inode, 1); > > I don't think that is correct. AFAIK the layoutcommit is needed to > get back to the data after a crash - basically the only thing a > !datasync fsync can skip is dirty timestamps. Hi Christoph, We had a spec clarification about this recently. The result is that for 'files' layout types: 1) DATA_SYNC writes and unstable writes with COMMIT must store enough data to disk to allow the server to recover the data if it crashes (i.e. it provides the equivalent of O_DSYNC and/or fdatasync()). FILE_SYNC writes must commit all data + metadata (i.e. they do the equivalent of O_SYNC writes). 2) This means that layoutcommit is only needed when the layout specifies COMMIT to the data servers, or if the writes to the data servers return a DATA_SYNC. All it does is commit the time stamps + file size to disk on the metadata server (and so you avoid the need to do an expensive recovery process on crash). IOW: the above should be correct. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- 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
