Thanks for reply. I think mnt_slave and mnt_master are integrity parts
of master/slave semantics and put the 2 lines together will make the
logic clearer.
Many thanks.
2012/6/22 Al Viro <viro@xxxxxxxxxxxxxxxxxx>:
> 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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