On Wed, Jan 15, 2014 at 7:19 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > On Wed, Jan 08, 2014 at 11:10:09PM +0100, Miklos Szeredi wrote: >> From: Miklos Szeredi <mszeredi@xxxxxxx> >> >> If this flag is specified and the target of the rename exists then the >> rename syscall fails with EEXIST. > > Why is this useful? > > (I'm sure it is, it'd just be useful to have the reasons recorded > someplace.) > >> The VFS does the existence checking, so it is trivial to enable for most >> local filesystems. This patch only enables it in ext4. >> >> For network filesystems the VFS check is not enough as there may be a race >> between a remote create and the rename, so these filesystems need to handle >> this flag in their ->rename() implementations to ensure atomicity. > > Till that's done this should probably result in -EOPNOTSUPP on those > filesystems? > > I think this would need new protocol in the NFS case. Yes, it needs to be enabled on a case-by-case basis. Only enabled for ext4 now, but trivial to do for most fs. Thanks, Miklos -- 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
