On Tue, Aug 21, 2012 at 02:49:47PM +0400, Pavel Emelyanov wrote: > On 08/21/2012 02:42 PM, Aneesh Kumar K.V wrote: > > Pavel Emelyanov <xemul@xxxxxxxxxxxxx> writes: > > > >> On 08/20/2012 11:32 PM, J. Bruce Fields wrote: > >>> On Mon, Aug 20, 2012 at 11:06:06PM +0400, Cyrill Gorcunov wrote: > >>>> On Mon, Aug 20, 2012 at 02:32:25PM -0400, J. Bruce Fields wrote: > >>>>> On Mon, Aug 20, 2012 at 08:33:38PM +0400, Cyrill Gorcunov wrote: > >>>>>> On Mon, Aug 20, 2012 at 07:49:23PM +0530, Aneesh Kumar K.V wrote: > >>>>>>> Cyrill Gorcunov <gorcunov@xxxxxxxxxx> writes: > >>>>>>> > >>>>>>>> To provide fsnotify object inodes being watched without > >>>>>>>> binding to alphabetical path we need to encode them with > >>>>>>>> exportfs help. This patch adds a helper which operates > >>>>>>>> with plain inodes directly. > >>>>>>> > >>>>>>> doesn't name_to_handle_at() work for you ? It also allows to get a file > >>>>>>> handle using file descriptor. > >>>>>> > >>>>>> Hi, sorry for dealy. Well, the last idea is to get rid of this helper, > >>>>>> I've sent out an updated version where ino+dev is only printed. > >>>>> > >>>>> I don't understand how ino and dev are useful to you, though, if you're > >>>>> still hoping to be able to look up inodes using this information later > >>>>> on. > >>>> > >>>> Hi Bruce, I believe having ino+dev is better than nothing. Otherwise we > >>>> simply have no clue which targets are bound to inotify mark. Sometime > >>>> (!) we can try to generate fhandle in userspace from this ino+dev bundle > >>>> and then open the target file. > >>> > >>> That's insufficient to generate a filehandle in general. > >> > >> Yes, sure, but for live migration having inode and device is enough and that's why. > >> We can use two ways of having a filesystem on the target machine in the same > >> state (from paths points of view) as it was on destination one: > >> > >> 1. copy file tree in a rsync manner > >> 2. copy a virtual disk image file > >> > >> In the 1st case we can map inode number to path easily, since we iterate over a filesystem OK. Then you don't care about unlinked files? If the filesystem's frozen by the time you get here, I suppose you could also just use paths? > >> anyway. I agree, that rsync is not perfect for migration but still. > >> > >> In the 2nd case we can generate filehandle out of an inode number only since we _do_ know > >> that inode will not get reused. > > > > If you are going to to use open_by_handle, then that handle is not > > sufficient right ? Or do you have open_by_inode ? as part of c/r ? > > Why? For e.g. ext4 you can construct a handle in userspace and open by it. If it's a real filehandle you want, in general you don't want to construct it in userspace--depending on the filesystem it may require filesystem-specific knowledge. --b. > > >> > >> However, if you have some better ideas on what information about inode should be exported > >> to the userspace please share. > >> > > > > Why not use name_to_handle(fd,...) and open_by_handle(handle,..) ? > > Because we don't have an fd at hands by the time we need to know the handle. > > > > >>> (Also: there's the usual inode-number aliasing problem: the inode number > >>> could get reused by another file. Unless you know the file is being > >>> held open the whole time.) > >>> > > > > -aneesh > > > > . > > > > Thanks, > Pavel -- 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
