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    SubjectRe: [RFC/PATCH 2/8] revoke: inode revoke lock V7
    Quoting Pekka J Enberg (penberg@cs.helsinki.fi):
    > Hi,
    >
    > On Wed, 19 Dec 2007, Serge E. Hallyn wrote:
    > > > I assume you mean S_REVOKE_LOCK and not ->i_mutex, right?
    > >
    > > No I did mean the i_mutex since you take the i_mutex when you set
    > > S_REVOKE_LOCK. So between that and the comment above do_lookup(),
    > > I assumed you were trying to lock out concurrent do_lookups() returning
    > > an inode whose revoke is starting at the same time.
    >
    > No, I only use ->i_mutex for synchronizing the write to ->i_flags.

    duh.

    > On Wed, 19 Dec 2007, Serge E. Hallyn wrote:
    > > > The caller is supposed to block open(2) with chmod(2)/chattr(2) so while
    > > > revoke is in progress, you can get references to the _revoked inode_,
    > > > which is fine (operations on it will fail with EBADFS). The
    > > > ->i_revoke_wait bits are there to make sure that while we revoke, you
    > > > can't get a _new reference_ to the inode until we're done.
    > >
    > > And a new reference means through iget(), so if revoke starts
    > > between the IS_REVOKE_LOCKED() check in do_lookup and its return,
    > > it's ok bc we'll get a reference later on?
    >
    > Yes, as soon as we unhash the dentries and the inode, do_lookup() will try
    > to find a new inode with iget() but we need to wait before writeback on
    > the revoked inode is finished.

    Ok, that makes sense. I'll let that sit for a short while and look
    again :)

    thanks,
    -serge

    > On Wed, 19 Dec 2007, Serge E. Hallyn wrote:
    > > I'm a little confused but i'll keep looking.
    >
    > I don't blame you. The patch is missing the following "minor detail" which
    > is needed to avoid fs corruption...
    >
    > Pekka
    >
    > Index: 2.6/fs/revoke.c
    > ===================================================================
    > --- 2.6.orig/fs/revoke.c 2007-12-16 19:57:40.000000000 +0200
    > +++ 2.6/fs/revoke.c 2007-12-19 18:03:13.000000000 +0200
    > @@ -426,6 +426,8 @@ int err = 0;
    > make_revoked_inode(inode);
    > remove_inode_hash(inode);
    > revoke_aliases(inode);
    > +
    > + err = write_inode_now(inode, 1);
    > failed:
    > revoke_unlock(inode);
    > wake_up(&inode->i_revoke_wait);


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