This adds a new dlmglue lock type which is intended to back flock()
requests.
Since these locks are driven from userspace, usage rules are much more
liberal than the typical Ocfs2 internal cluster lock. As a result, we can't
make use of most dlmglue features - lock caching and lock level
optimizations in particular. Additionally, userspace is free to deadlock
itself, so we have to deal with that in the same way as the rest of the
kernel - by allowing a signal to abort a lock request.
In order to keep ocfs2_cluster_lock() complexity down, ocfs2_file_lock()
does it's own dlm coordination. We still use the same helper functions
though, so duplicated code is kept to a minimum.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Ocfs2 currently does cluster-wide node messaging to check the open state of
an inode during delete. This patch removes that mechanism in favor of an
inode cluster lock which is taken at shared read when an inode is first read
and dropped in clear_inode(). This allows a deleting node to test the
liveness of an inode by attempting to take an exclusive lock.
Signed-off-by: Tiger Yang <tiger.yang@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Replace the dentry vote mechanism with a cluster lock which covers a set
of dentries. This allows us to force d_delete() only on nodes which actually
care about an unlink.
Every node that does a ->lookup() gets a read only lock on the dentry, until
an unlink during which the unlinking node, will request an exclusive lock,
forcing the other nodes who care about that dentry to d_delete() it. The
effect is that we retain a very lightweight ->d_revalidate(), and at the
same time get to make large improvements to the average case performance of
the ocfs2 unlink and rename operations.
This patch adds the cluster lock type which OCFS2 can attach to
dentries. A small number of fs/ocfs2/dcache.c functions are stubbed
out so that this change can compile.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
