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 this is what you meant than seems ok to me. Thanks, Amir. -- 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
