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 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. However, if you have some better ideas on what information about inode should be exported to the userspace please share. > (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.) > > --b. > . > 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
