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    SubjectRe: [GIT PULL] 9p file system bug fixes for 2.6.35-rc2

    On Tue, 8 Jun 2010, Al Viro wrote:

    > On Mon, Jun 07, 2010 at 05:08:19PM -0700, Linus Torvalds wrote:
    > > In fact, the other thing that I find doing that whole "dentry->d_parent"
    > > thing seems to literally be broken. If you look at v9fs_fid_lookup(),
    > > you'll notice how it walks up the d_parent chain, and at that point you do
    > > NOT own the directory i_mutex, so at that point d_parent really _can_ be
    > > changing wildly due to concurrent renames or whatever.
    > Eh... It's bogus, all right, but i_mutex is not the correct solution.

    Oh, no, I didn't imply it was. But the other sites that I saw doing
    the dentry->d_parent access already _had_ the i_mutex thing, so I was
    pointing out how this one does not (and indeed _cannot_ do that).

    So I'm just saying that pretty much _all_ the dentry->d_parent use in 9p
    seems very suspect. The cases where we hold i_mutex (because the caller
    already took it) shouldn't do that whole d_parent dance, because they get
    the directory inode passed into them directly.

    And the other places are just buggy.

    So from a quick look, the use of d_parent in 9p is simply not a good idea.


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