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    SubjectRe: [RFC] Patch to allow distributed flock
    På to , 24/06/2004 klokka 19:10, skreiv Ken Preslan:
    > Hi,
    > I'd like to start a discussion about changing the VFS so it allows
    > flocks to be enforced between machines in a cluster filesystem (such as
    > GFS). The purpose of GFS it so allow local filesystem semantics
    > to a filesystem shared between the nodes of a cluster of tightly-coupled
    > machines. As such, flock is probably expected to work across the cluster.
    > What are everyone's thoughts on a patch such as this?

    If you defer updating the VFS until after the ->lock() call returns,
    then it makes it difficult to protect yourself against races (as I
    argued about the POSIX lock interface on the list yesterday).

    If you have the underlying filesystem call flock_lock_file() itself,
    then that gives it the freedom to implement its own locking scheme
    around that call.
    For instance NFS has a thread that is supposed to reclaim locks if the
    server reboots. We take a non-exclusive lock on an rwsem to ensure that
    we block it while there are outstanding locking RPC calls, however that
    rwsem has to be released before we return from the ->lock() call, and so
    there exists a race after the rwsem was released until the
    inode->i_flock list is updated.

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      Last update: 2005-03-22 14:04    [W:0.022 / U:1.312 seconds]
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