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    Subject[PATCH 29/41] union-mount: Always create topmost directory on open
    Date
    When we open a directory, always create a matching directory on the
    top-level. This way we don't have to go back and create all the
    directories on the path to an element when we want to copy it up.

    XXX - Turn into #ifdef'able function

    Signed-off-by: Jan Blunck <jblunck@suse.de>
    Signed-off-by: Valerie Aurora <vaurora@redhat.com>
    ---
    fs/namei.c | 34 ++++++++++++++++++++++++++++++----
    1 files changed, 30 insertions(+), 4 deletions(-)

    diff --git a/fs/namei.c b/fs/namei.c
    index 1f2a214..8d95eb1 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -1284,8 +1284,31 @@ static int __link_path_walk(const char *name, struct nameidata *nd)
    if (err)
    break;

    - if ((nd->flags & LOOKUP_TOPMOST) &&
    - (nd->um_flags & LAST_LOWLEVEL)) {
    + /*
    + * We want to create this element on the top level
    + * file system in two cases:
    + *
    + * - We are specifically told to - LOOKUP_TOPMOST.
    + * - This is a directory, and it does not yet exist on
    + * the top level. Various tricks only work if
    + * directories always exist on the top level.
    + *
    + * In either case, only create this element on the top
    + * level if the last element is located on the lower
    + * level. If the last element is located on the top
    + * level, then every single element in the path
    + * already exists on the top level.
    + *
    + * Note that we can assume that the parent is on the
    + * top level since we always create the directory on
    + * the top level.
    + */
    +
    + if ((nd->um_flags & LAST_LOWLEVEL) &&
    + ((next.dentry->d_inode &&
    + S_ISDIR(next.dentry->d_inode->i_mode) &&
    + (nd->path.mnt != next.mnt)) ||
    + (nd->flags & LOOKUP_TOPMOST))) {
    struct dentry *dentry;

    dentry = union_create_topmost(nd, &this, &next);
    @@ -1349,8 +1372,11 @@ last_component:
    if (err)
    break;

    - if ((nd->flags & LOOKUP_TOPMOST) &&
    - (nd->um_flags & LAST_LOWLEVEL)) {
    + if ((nd->um_flags & LAST_LOWLEVEL) &&
    + ((next.dentry->d_inode &&
    + S_ISDIR(next.dentry->d_inode->i_mode) &&
    + (nd->path.mnt != next.mnt)) ||
    + (nd->flags & LOOKUP_TOPMOST))) {
    struct dentry *dentry;

    dentry = union_create_topmost(nd, &this, &next);
    --
    1.6.3.3


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