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SubjectRe: [PATCH 2/4] vfs: keep list of mounts for each superblock
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On Wed, 2011-08-03 at 23:17 +0100, Al Viro wrote:
> On Wed, Aug 03, 2011 at 12:48:39PM +0200, Miklos Szeredi wrote:
> > @@ -696,6 +696,11 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
> > mnt->mnt_sb = root->d_sb;
> > mnt->mnt_mountpoint = mnt->mnt_root;
> > mnt->mnt_parent = mnt;
> > +
> > + br_write_lock(vfsmount_lock);
> > + list_add_tail(&mnt->mnt_instance, &mnt->mnt_sb->s_mounts);
> > + br_write_unlock(vfsmount_lock);
>
> Racy.
>
> > @@ -745,6 +750,10 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
> > if (!list_empty(&old->mnt_expire))
> > list_add(&mnt->mnt_expire, &old->mnt_expire);
> > }
> > +
> > + br_write_lock(vfsmount_lock);
> > + list_add_tail(&mnt->mnt_instance, &mnt->mnt_sb->s_mounts);
> > + br_write_unlock(vfsmount_lock);
>
> Ditto. If you expect to be able to find *all* vfsmounts over given sb,
> this locking is simply wrong.

I don't understand. All accesses to mnt_instance/s_mounts are protected
by vfsmount_lock. What else is needed?

Thanks,
Miklos




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