On Thu, Aug 16, 2012 at 04:38:14PM +0400, Cyrill Gorcunov wrote: > On Thu, Aug 16, 2012 at 10:24:48AM +0400, Cyrill Gorcunov wrote: > > > > > On the other hand, if you want a real filehandle then wouldn't you want > > > > > to e.g. call the filesystem's ->encode_fh() if necessary, as > > > > > exportfs_encode_fh() does? > > > > > > > > Well, one of the problem I hit when I've been trying to use encode_fh > > > > is that every new implementation of encode_fh will require some size > > > > (even unknown) in buffer where encoded data pushed. Correct me please > > > > if I'm wrong. But with export_encode_inode_fh there is a small buffer > > > > with pretty known size needed on stack needed for printing data in > > > > fdinfo. > > > > > > You can just give encode_fh a too-small data and let it fail if it's not > > > big enough. > > > > > > (In practice I think everyone supports NFSv3 filehandles which have a > > > maximum size of 64 bytes.) > > > > I'll think about it, thanks! > > Hi Bruce, thinking a bit more I guess using general encode_fh is not that > convenient since it operates with dentries while our fdinfo output deals > with inodes. Thus I should either provide some new encode_fh variant > which would deal with inodes directly without "parents". I can't see why that wouldn't work. > Which doesn't > look for me anyhow better than the new export_encode_inode_fh helper. That isn't going to work for filesystems that define their own encode_fh: $ git grep '\.encode_fh' fs/btrfs/export.c: .encode_fh = btrfs_encode_fh, fs/ceph/export.c: .encode_fh = ceph_encode_fh, fs/fat/inode.c: .encode_fh = fat_encode_fh, fs/fuse/inode.c: .encode_fh = fuse_encode_fh, fs/gfs2/export.c: .encode_fh = gfs2_encode_fh, fs/isofs/export.c: .encode_fh = isofs_export_encode_fh, fs/nilfs2/namei.c: .encode_fh = nilfs_encode_fh, fs/ocfs2/export.c: .encode_fh = ocfs2_encode_fh, fs/reiserfs/super.c: .encode_fh = reiserfs_encode_fh, fs/udf/namei.c: .encode_fh = udf_encode_fh, fs/xfs/xfs_export.c: .encode_fh = xfs_fs_encode_fh, mm/shmem.c: .encode_fh = shmem_encode_fh, --b. > After all, if the use of encode_fh become a mandatory rule we can easily > extend fsnotify fdinfo output to support new scheme without breaking > user space, because output looks like > > | fhandle-type: 1 f_handle: 49b1060023552153 > > (ie if something is changed than these fields will be simply updated). > > Or maybe I miss something? > > Cyrill -- 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
