On Mon, 03 May 2010 16:12:26 PDT, Valerie Aurora said:
> When a file on the read-only layer of a union mount is altered, it
> must be copied up to the topmost read-write layer. This patch creates
> union_copyup() and its supporting routines.
> ---
> fs/union.c | 244 +++++++++++++++++++++++++++++++++++++++++++++++
> +/**
> + * union_copyup_data - Copy up len bytes of old's data to new
> + *
> + * @old: source file
> + * @new: target file
> + * @len: number of bytes to copy
> + */
> +
> +static int union_copyup_data(struct path *old, struct vfsmount *new_mnt,
> + struct dentry *new_dentry, size_t len)
> +{
> + struct file *old_file;
> + struct file *new_file;
> + const struct cred *cred = current_cred();
> + loff_t offset = 0;
> + long bytes;
> + int error;
Should this be 'int error = 0;' ?
> +
> + if (len == 0)
> + return 0;
> +
> + /* Get reference to balance later fput() */
> + path_get(old);
> + old_file = dentry_open(old->dentry, old->mnt, O_RDONLY, cred);
> + if (IS_ERR(old_file))
> + return PTR_ERR(old_file);
> +
> + dget(new_dentry);
> + mntget(new_mnt);
> + new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred);
> + if (IS_ERR(new_file)) {
> + error = PTR_ERR(new_file);
> + goto out_fput;
> + }
> +
> + bytes = do_splice_direct(old_file, &offset, new_file, len,
> + SPLICE_F_MOVE);
> + if (bytes < 0)
> + error = bytes;
> +
> + fput(new_file);
> +out_fput:
> + fput(old_file);
> + return error;
> +}
because otherwise if do_splice_direct() returns a non-negative value,
we can hit 'return error;' without ever having set error to anything?
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