Hello Professor Zadok,
Erez Zadok:
I believe that small VFS changes to help stackable file systems are
perfectly reasonable, and a good thing; and I'm working on such patches.
Conversely, I am very mindful of the VFS's complexity, so I also believe
that massive VFS changes are a bad thing; I
Dear Junjiro, thanks for your comments. I am familiar with the issues and
techniques you mention below, and more. To properly address your comments,
I had to explain some background before addressing each of your points. So
my apologies in advance to everyone for the length of this reply.
Al, Christoph, and Andrew,
As per your request, I'm posting for review the unionfs code (and related
code) that's in my korg tree against mainline (v2.6.24-rc4-190-g94545ba).
This code is nearly identical to what's in -mm (the mm code has a couple of
additional things that depend on mm-specific
Erez Zadok:
(1) Cache coherency: by far, the biggest concern had been around cache
:::
unionfs. The solution we have implemented is to compare the mtime/ctime of
upper/lower objects during revalidation (esp. of dentries); and if the lower
times are newer, we reconstruct the union
