Valerie Aurora: > One of the major difficulties that arises even when doing unioning at > the VFS level is keeping around the parent's path in order to do the > copyup later on. Take a look at the code pattern in the "union-mount: > Implement union-aware syscall()" series of patches. That's the > prettiest and most efficient version I could come up with, after two > other implementations, and it's in the VFS, at the vfs_foo_syscall() > level. I don't even know how I would start if I had to wait until the > file system op is called. I agree that is prettiest, and copup at open for write makes it easier. But some applications issue mmap(MAP_PRIVATE) after open(O_RDWR), for example modprobe(8). In this case, every kernel module will be copied-up and it must be a waste of time and space. And I guess this is one reason why other implementation took the approach of copyup at write. At the same time, I guess this issue may be less important since other parts are pretty enough. 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
