[Linux-cluster] Re: GFS

[Pekka J Enberg]

David Teigland writes:
> 
>                  if (!dumping)
>                         down_read(&mm->mmap_sem);
> > > +
> > > +             for (vma = find_vma(mm, start); vma; vma = vma->vm_next)  {
> > > +                     if (end <= vma->vm_start)
> > > +                             break;
> > > +                     if (vma->vm_file &&
> > > +                         vma->vm_file->f_dentry->d_inode->i_sb == sb)  {
> > > +                             num_gh++;
> > > +                     }
> > > +             }
> > > +
> > > +             ghs = kmalloc((num_gh + 1) * sizeof(struct gfs2_holder),
> > > +                           GFP_KERNEL);
> > > +             if (!ghs) {
> > > +                     if (!dumping)
> > > +                             up_read(&mm->mmap_sem);
> > > +                     return -ENOMEM;
> > > +             }
> > > +
> > > +             for (vma = find_vma(mm, start); vma; vma = vma->vm_next) {
> > 
> > Sorry if this is an obvious question but what prevents another thread from 
> > doing mmap() before we do the second walk and messing up num_gh?  
> 
> mm->mmap_sem ?

Aah, I read that !dumping expression the other way around. Sorry and thanks. 

                           Pekka