Messages in this thread | | | Subject | Re: [RFC PATCH 5/10] vfs: shared subtree aware bind mounts | From | Ram Pai <> | Date | Tue, 20 Sep 2005 00:56:14 -0700 |
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On Tue, 2005-09-20 at 00:17, Al Viro wrote: > On Fri, Sep 16, 2005 at 11:26:19AM -0700, Ram wrote: > > This patch needs to be split *AND* accompanied by locking rules. It's > pretty much the core of the entire thing; if it's possible to offload > chunks elsewhere, life would become easier. Locking rules are badly > needed, along with the comments re "why can't that mntput()/dput() > block under a spinlock", etc.
Yes will do.
Also I realized that vfspnode_lock just added more complexity because all it protected was already protected by vfsmount_lock. So I am cleaning up that lock.
> > BTW, how are you dealing with MS_MOVE? In the patch #6 MS_MOVE and pivot_root are handled. > > > +void do_detach_prepare_mnt(struct vfsmount *mnt) > > +{ > > + mnt->mnt_mountpoint->d_mounted--; > > + mntput(mnt->mnt_parent); > > + dput(mnt->mnt_mountpoint); > > + mnt->mnt_parent = mnt; > > +} > > General note: mntput() should go _after_ dput() when we deal with pairs. > Doesn't cost anything, trivially safe.
ok
> > > if (res) { > > spin_lock(&vfsmount_lock); > > + clean_propagation_reference(res); > > Uh-oh... What makes that safe? We do mntput() here; are we guaranteed > that these pointers won't be the last references?
Yes it is safe and it is not releasing the last reference to the mount. Will put in a comment there.
It is releasing a reference to source mount of the bind operation.
static void inline clean_propagation_reference(struct vfsmount *mnt) +{ + struct vfsmount *p; + for (p = mnt; p; p = next_mnt(p, mnt)) + if (p->mnt_master) + mntput(p->mnt_master); +} +
> > + spin_lock(&vfspnode_lock); > > + propagate_abort_mount(m); > > Calls do_detach_prepare() -> dput(), mntput(). At the very least such > cases need comments... >
ok will add a comment. but propagate_abort_mount() is not holding vfsmount_lock, it is holding vfspnode_lock. So there should be a problem. But as mentioned earlier, even the need for vfspnode_lock is not needed.
> > +static void __do_make_private(struct vfsmount *mnt) > > +{ > > + __do_make_slave(mnt); > > + list_del_init(&mnt->mnt_slave); > > + mnt->mnt_master = NULL; > > + set_mnt_private(mnt); > > +} > > + > > int do_make_private(struct vfsmount *mnt) > > { > > /* > > * a private mount is nothing but a > > * slave mount with no incoming > > * propagations. > > */ > > spin_lock(&vfspnode_lock); > > - __do_make_slave(mnt); > > - list_del_init(&mnt->mnt_slave); > > + __do_make_private(mnt); > > spin_unlock(&vfspnode_lock); > > - mnt->mnt_master = NULL; > > - set_mnt_private(mnt); > > return 0; > > } > > Why not do that from the very beginning, BTW?
can be done. will do.
> > > /* > > - * a unclonable mount is nothing but a > > + * a unclonable mount is a > > * private mount which is unclonnable. > > */ > > spin_lock(&vfspnode_lock); > > - __do_make_slave(mnt); > > - list_del_init(&mnt->mnt_slave); > > + __do_make_private(mnt); > > spin_unlock(&vfspnode_lock); > > - mnt->mnt_master = NULL; > > set_mnt_unclonable(mnt); > > return 0; > > } > - > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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