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    Subject[PATCH 30/35] union-mount: Implement union-aware writable open()
    Date
    Copy up a file when opened with write permissions.  Does not copy up
    the file data when O_TRUNC is specified.
    ---
    fs/namei.c | 28 ++++++++++++++++++++++++++++
    1 files changed, 28 insertions(+), 0 deletions(-)

    diff --git a/fs/namei.c b/fs/namei.c
    index a6f7d5d..85a5451 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -1929,6 +1929,24 @@ exit:
    return ERR_PTR(error);
    }

    +static int open_union_copyup(struct nameidata *nd, struct path *path,
    + int open_flag)
    +{
    + struct vfsmount *oldmnt = path->mnt;
    + int error;
    +
    + if (open_flag & O_TRUNC)
    + error = union_copyup_len(nd, path, 0);
    + else
    + error = union_copyup(nd, path);
    + if (error)
    + return error;
    + if (oldmnt != path->mnt)
    + mntput(nd->path.mnt);
    +
    + return error;
    +}
    +
    static struct file *do_last(struct nameidata *nd, struct path *path,
    int open_flag, int acc_mode,
    int mode, const char *pathname,
    @@ -1979,6 +1997,11 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
    error = -ENOTDIR;
    if (*want_dir && !path->dentry->d_inode->i_op->lookup)
    goto exit_dput;
    + if (acc_mode & MAY_WRITE) {
    + error = open_union_copyup(nd, path, open_flag);
    + if (error)
    + goto exit_dput;
    + }
    path_to_nameidata(path, nd);
    audit_inode(pathname, nd->path.dentry);
    goto ok;
    @@ -2050,6 +2073,11 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
    if (path->dentry->d_inode->i_op->follow_link)
    return NULL;

    + if (acc_mode & MAY_WRITE) {
    + error = open_union_copyup(nd, path, open_flag);
    + if (error)
    + goto exit_dput;
    + }
    path_to_nameidata(path, nd);
    error = -EISDIR;
    if (S_ISDIR(path->dentry->d_inode->i_mode))
    --
    1.6.3.3


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