On Mon, May 03, 2010 at 09:40:04PM -0400, Valdis.Kletnieks@xxxxxx wrote:
> 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?
Yes, I think you're right. Thanks!
-VAL
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