Miklos Szeredi: > Please consider overlayfs for inclusion into 3.10. Thank you for CCing me. First, I'd suggest you to follow some recent activities in mainline kernel such as - MODULE_ALIAS_FS - file_inode() - d_weak_revalidate() which may not be necessary for overlayfs as long as it prohibit users the direct-access to layers (bypassing overlayfs). > It's included in Ubuntu and openSUSE, used by OpenWrt and various other > projects. I regularly get emails asking when it will be included in mainline. Such situation is very similar which AUFS had a few years ago. At that time, AUFS was rejected since UnionMount was chosen. Years passed, the development of UnionMount seems to stop and linux mainline doesn't have generic stackable filesytem yet. I had pointed out some defects in overlayfs (and UnionMount too). They are all based upon the "name-based" behaviour instead of "inode-based" one. Other than "Non-standard behavior" in the overlayfs document, the are, for example, - read(2) may get an obsoleted filedata (fstat(2) for metadata too). - fcntl(F_SETLK) may be broken by copy-up. - inotify may not work when it refers to the file before being copied-up. - unnecessary copy-up may happen, for example mmap(MAP_PRIVATE) after open(O_RDWR). AUFS is an "inode-based" stackable filesystem and solved them many years ago. But I have to admit that AUFS is big. Yes it is grown up. I don't stop including overlayfs into mainline, but if the development of UnionMount is really stopped, then I'd ask people to consider merging aufs as well as overlayfs. J. R. Okajima -- 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
