Messages in this thread | | | From | "J. R. Okajima" <> | Subject | Re: [overlayfs/port] overlayfs: v13 port attempt to kernel 3.5 | Date | Mon, 20 Aug 2012 19:38:18 +0900 |
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Sedat Dilek: > The other part to run a Linux live-system is a "Union FileSystem" - > this part is missing (speaking of upstream). > > Since years AUFS seems to be the choice #1 in a lot of distros to > workaround the problem. > NOTE: AUFS was rejected from upstream (to say not accepted).
Exactly. The reason was that linux rejects all union-type filesystems but UnionMount (which is union-type mount). Later, the development of UnionMount seems to be almost stopped. The essential design of overlayfs is based upon UnionMount, and I have pointed out several issues such as - for users, the inode number may change silently. eg. copy-up. - hardlinks may break by copy-up. - read(2) may get an obsoleted filedata (fstat(2) for metadata too). - fcntl(F_SETLK) may be broken by copy-up. - unnecessary copy-up may happen, for example mmap(MAP_PRIVATE) after open(O_RDWR). - Later I noticed one more thing. /proc/PID/{fd/,exe} may not work correctly for overlayfs ... - etc... They are called "unPOSIXy behavior", and unforunately many of them are NOT seem to be addressed in recent patches either.
Also I have posted If the development of UnionMount is really stopped, then I'd ask people to consider merging aufs as well as overlayfs. but I am not sure whether LKML people are still waiting for UnionMount and rejecting aufs.
J. R. Okajima
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