Today an inode's items are deleted once its nlink reaches zero and the
final iput is called in a local mount. This can delete inodes from
under other mounts which have opened the inode before it was unlinked on
another mount.
We fix this by adding cached inode tracking. Each mount maintains
groups of cached inode bitmaps at the same granularity as inode locking.
As a mount performs its final iput it gets a bitmap from the server
which indicates if any other mount has inodes in the group open.
This makes the two fast paths of opening and closing linked files and of
deleting a file that was unlinked locally only pay a moderate cost of
either maintaining the bitmap locally and only getting the open map once
per lock group. Removing many files in a group will only lock and get
the open map once per group.
Signed-off-by: Zach Brown <zab@versity.com>
22371fe5bd