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    Subject[PATCH] EXPORTFS: handle NULL returns from fh_to_dentry()/fh_to_parent()
    From
    From: J. Bruce Fields <bfields@citi.umich.edu>

    While 440037287c5 "[PATCH] switch all filesystems over to
    d_obtain_alias" removed some cases where fh_to_dentry() and
    fh_to_parent() could return NULL, there are still a few NULL returns
    left in individual filesystems. Thus it was a mistake for that commit
    to remove the handling of NULL returns in the callers.

    Revert those parts of 440037287c5 which removed the NULL handling.

    (We could, alternatively, modify all implementations to return -ESTALE
    instead of NULL, but that proves to require fixing a number of
    filesystems, and in some cases it's arguably more natural to return
    NULL.)

    Thanks to David for original patch and Linus, Christoph, and Hugh for
    review.

    Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
    Cc: David Howells <dhowells@redhat.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Hugh Dickins <hugh@veritas.com>
    ---
    fs/exportfs/expfs.c | 4 ++++
    1 files changed, 4 insertions(+), 0 deletions(-)

    On Fri, Dec 05, 2008 at 11:02:00AM -0800, Linus Torvalds wrote:
    > So it really seems to make more sense to just make the ESTALE handling be
    > a NFS issue.

    This thread seems to have died out, and I didn't see any objections to
    handling the error in the caller as Linus suggested, so here's the
    patch.

    Also available from the for-2.6.28 branch at

    git://linux-nfs.org/~bfields/linux.git for-2.6.28

    --b.

    diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
    index 80246ba..890e018 100644
    --- a/fs/exportfs/expfs.c
    +++ b/fs/exportfs/expfs.c
    @@ -367,6 +367,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
    * Try to get any dentry for the given file handle from the filesystem.
    */
    result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
    + if (!result)
    + result = ERR_PTR(-ESTALE);
    if (IS_ERR(result))
    return result;

    @@ -420,6 +422,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,

    target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
    fh_len, fileid_type);
    + if (!target_dir)
    + goto err_result;
    err = PTR_ERR(target_dir);
    if (IS_ERR(target_dir))
    goto err_result;
    --
    1.5.5.rc1

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