Re: [RFC][PATCH 10/14] In-kernel file copy between union mounted filesystems

Jan Engelhardt
2007-05-16T07:59:22Z

On May 14 2007 15:13, Bharata B Rao wrote:
>+
>+ if (flag & 0x2) {
>+ error = union_copyup(nd, flag);
>+ if (error)
>+ goto exit;
>+ }

What I dislike (and that also goes for fs/namei.c and such) that they use
numeral constants, i.e. 0x2. That seems error-prone. Could this (and
the in-kernel users of 0x1/0x2/0x4) be turned into some constant?

>+ if (IS_DEADDIR(parent->d_inode))
>+ goto error;
>+ err = -EACCES; /* shouldn't it be ENOSYS? */

I do not think so. ENOSYS means Syscall not implemented. But it is
implemented. If ->i_op is not there does not imply ENOSYS.

Though, now that I grep through fs/*, I see that namei.c also
has that comment "shouldn't it be ENOSYS", so it's all at odds.

>+ if (!parent->d_inode->i_op || !parent->d_inode->i_op->create)
>+ goto error;

>+struct dentry * union_create_topmost(struct nameidata *nd, struct dentry *old)
>+{
>+ struct dentry *dentry;
>+ struct dentry *parent = nd->dentry;
>+
>+ UM_DEBUG_UID("dentry=%s\n", old->d_name.name);
>+
>+ BUG_ON(parent->d_sb == old->d_sb);
>+ if (!S_ISREG(old->d_inode->i_mode)) {
>+ UM_DEBUG("This filetype isn't supported!\n");

Does that mean I cannot create block devices, etc.?

>+int union_copy_file(struct dentry *old_dentry, struct vfsmount *old_mnt,
>+ struct dentry *new_dentry, struct vfsmount *new_mnt)
>+{
>+ int ret;
>+ size_t size;
>+ loff_t offset;
>+ struct file *old_file, *new_file;
>[...]
>+ size = i_size_read(old_file->f_path.dentry->d_inode);
>+ if (((size_t)size != size) || ((ssize_t)size != size)) {

No need to cast, size is already size_t. And then that left part
is somewhat superfluous.

>+ ret = -EFBIG;
>+ goto fput_new;
>+ }
>+

Jan
--