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    SubjectRe: [PATCH 3/9] VFS: Introduce a mount context
    Date
    Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

    > > + if (fs_type->fsopen && fs_type->mc_size < sizeof(*mc))
    > > + BUG();
    >
    > So ->mc_size can be 0 (i.e. not explicitly initialized) if fs_type does
    > not have ->fsopen. OK.

    I need to be able to handle filesystems that don't support this yet. Once all
    filesystems support this, I would be able to take away the max_t() thing.

    > > + if (!src->ops->dup)
    > > + return ERR_PTR(-ENOTSUPP);
    > > +
    > > + mc = kmemdup(src, src->fs_type->mc_size, GFP_KERNEL);
    >
    > So this assumes that vfs_dup_mount_context is only used if ->mc_size is
    > explicitly initialized. A max_t here as well probably wouldn't hurt.

    If you don't provide an ->fsopen() op, you can't set src->ops, you don't see a
    mount context and you can't call this function. If you did supply an
    ->fsopen() op, the BUG() would've got you if you didn't set ->mc_size.

    > > + unsigned short mc_size; /* Size of mount context to allocate */
    >
    > Any particular reason to use a short? The struct doesn't pack any better.

    But it leaves a hole someone else can use. I try not to use fields larger
    than I need to.

    David

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