On Wed, Jun 20, 2012 at 10:54:00AM +0800, yushang wrote:
> Hi dear all,
> I have a question about the mnt_master logic in clone_mnt , look at
> following lines:
> ...
> } else if (!(flag & CL_PRIVATE)) {
> if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
> list_add(&mnt->mnt_share, &old->mnt_share);
> if (IS_MNT_SLAVE(old))
> list_add(&mnt->mnt_slave, &old->mnt_slave);
> mnt->mnt_master = old->mnt_master;
> }
> ...
> I think the following lines are equivalent, right ? or I've missed
> something ? many thanks!
> ...
> } else if (!(flag & CL_PRIVATE)) {
> if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
> list_add(&mnt->mnt_share, &old->mnt_share);
> if (IS_MNT_SLAVE(old)) {
> list_add(&mnt->mnt_slave, &old->mnt_slave);
> mnt->mnt_master = old->mnt_master;
> }
> }
Yes; we are guaranteed that mnt->master is NULL after alloc_vfsmnt(),
so that would be an equivalent transformation. Matter of taste,
mostly - performance win is negligible and IMO your variant is
slightly less explicit.
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