GitLab

Another ioctl feature, move-down.
The behaviour is, as you can guess, the opposite of copy-up.
The feature called FHSM (file-based hierarchical storage management, in
later commit) uses this ioctl aggressively.

See also the document in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Imagine a sequence such like this.
- user opens a file which exists on the lower readonly branch.
- user unlinks the file (still opened). its parent dir may be removed
  too.
- user writes something to the file.

Then aufs has to copy-up the unlinked file.
Note that the copy-up in aufs is not done in open(2) by default.
This commit handles this case by copy-up the file in write(2).
The target directory is the one which aufs created internally for this
purpose.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Copy-up the ancestors of the target.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Because the copy-up operation is big and has many parameters and
functions, consolidate them in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The functions for
- create the copy-up target file
- copy filedata
- copy metadata

In copying filedata, I had tried splice_direct() instead of repeating
read/write. Surprisingly, I could not see a big difference. So let's
keep this approach for a while. Someday SEEK_DATA/SEEK_HOLE become more
popular, it may help optimizing this read/write.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

Copy the inode attributes between branches.
See also the document in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

The generation of iinfo and dinfo inherit sbinfo's.
Also iinfo generation tracks the branch inode's generation to test the
matching after the branch management.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>