On Tue, Jan 30, 2018 at 10:05:08PM +0200, Amir Goldstein wrote: > On Tue, Jan 30, 2018 at 10:03 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > On Tue, Jan 30, 2018 at 9:33 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > >> On Tue, Jan 23, 2018 at 03:47:29PM +0200, Amir Goldstein wrote: > >>> On Tue, Jan 23, 2018 at 3:45 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > >>> > On Mon, Jan 22, 2018 at 09:46:33PM +0200, Amir Goldstein wrote: > >>> >> On Mon, Jan 22, 2018 at 9:34 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > >>> >> > On Mon, Jan 22, 2018 at 8:39 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > >>> >> >> There is a need to support metacopy dentry in midlayer. That means there > >>> >> >> could be a chain of metacopy dentries. > >>> >> >> > >>> >> >> For example, upper could be metacopy, midlayer lower could be metacopy and > >>> >> >> lowest layer could be actual data inode. This means when we copy up actual > >>> >> >> data, we should be able to reach to lowest data inode and copy up data from > >>> >> >> there. And that means we should keep track of all the dentries in origin > >>> >> >> chain which lead to data inode. > >>> >> >> > >>> >> >> Current ovl_check_origin() logic only looks for one origin dentry. This patch > >>> >> >> enhances ovl_check_origin() to continue to follow origin chain and return > >>> >> >> all the origin entries found. This is done only if caller of the function > >>> >> >> set "follow_chain" argument. > >>> >> >> > >>> >> > > >>> >> > We don't really need to keep the entire chain do we? > >>> >> > We can follow chain but keep only the one inode that is not a metacopy inode. > >>> >> > All the rest are useless, no? > >>> >> > Then we don't create a new type of object - non-dir with numlower > 1. > >>> >> > > >>> >> > >>> >> Seems like if you don't keep the entire chain, then no need for > >>> >> patches 14 and 15. > >>> > > >>> > I will need to have atleast 2 lower dentries. One will be top most > >>> > metadata copy and other lower most data dentry. IOW, both the ends of > >>> > the chain need to be there. > >>> > > >>> >> Also with upper metacopy, you can fix upper origin xattr after > >>> >> following to the data > >>> >> origin and forget about middle layer metacopies forever. > >>> > > >>> > If upper metacopy is alreday there, then I agree that lower top most > >>> > becomes inner node of chain and we can get rid of it. > >>> > > >>> >> > >>> >> Am I missing something? > >>> > > >>> > I think you are missing the case when there is no upper and lower has > >>> > a metacopy chain. In that case we need to retain two dentries. One for > >>> > data copy up and one for metadata copy up. > >>> > > >>> > >>> OK. so you can get rid of all the middle metacopies while following > >>> the origin chain. no reason to keep those. > >> > >> Hi Amir, > >> > >> What about the case when we have upper and one middle metacopy. As of top > >> most lower is the ORIGIN for upper. Should we retain that top most lower > >> ORIGIN as well as lower most data. Or just retain lower most data and > >> use that as ORIGIN. > >> > > > > Not sure I follow. > > IIUC, the longest possible chain is lowerstack size 2: > > upper -> metadata ORIGIN -> data ORIGIN > > > > If you are wondering if we could drop the metadata ORIGIN, > I think we need it at least for constant and persistent st_ino. Right, I was wondering can be drop metadata ORIGIN and just live with data ORIGIN. My initial impression is that constant and persistent st_ino can be achieved using just data ORIGIN alone as well. But I might be missing some finer detail. Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
