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. > 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
