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    Subject[PATCH 36/41] union-mount: Increment read-only users count for read-only layer
    Date
    Union mounts want to guarantee that the read-only layer is read-only -
    and stays read-only. Use the new superblock read-only user count.

    XXX - Put common code in loopback and regular mounts in a function

    Signed-off-by: Valerie Aurora <vaurora@redhat.com>
    ---
    fs/namespace.c | 13 +++++++++++++
    1 files changed, 13 insertions(+), 0 deletions(-)

    diff --git a/fs/namespace.c b/fs/namespace.c
    index 0280e5b..505974a 100644
    --- a/fs/namespace.c
    +++ b/fs/namespace.c
    @@ -1111,6 +1111,11 @@ static int do_umount(struct vfsmount *mnt, int flags)
    spin_unlock(&vfsmount_lock);
    if (retval)
    security_sb_umount_busy(mnt);
    + /* If this was a union mount, we are no longer a read-only
    + * user on the underlying mount */
    + if (mnt->mnt_flags & MNT_UNION)
    + mnt->mnt_parent->mnt_sb->s_readonly_users--;
    +
    up_write(&namespace_sem);
    release_mounts(&umount_list);
    return retval;
    @@ -1511,6 +1516,10 @@ static int do_loopback(struct path *path, char *old_name, int recurse,
    release_mounts(&umount_list);
    }

    + /* If this is a union mount, add ourselves to the readonly users */
    + if (mnt_flags & MNT_UNION)
    + mnt->mnt_parent->mnt_sb->s_readonly_users++;
    +
    out:
    up_write(&namespace_sem);
    path_put(&old_path);
    @@ -1730,6 +1739,10 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path,
    if ((err = graft_tree(newmnt, path)))
    goto unlock;

    + /* If this is a union mount, add ourselves to the readonly users */
    + if (mnt_flags & MNT_UNION)
    + newmnt->mnt_parent->mnt_sb->s_readonly_users++;
    +
    if (fslist) /* add to the specified expiration list */
    list_add_tail(&newmnt->mnt_expire, fslist);

    --
    1.6.3.3


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