[Linux-cluster] Re: GFS

[David Teigland <teigland redhat com>]

On Mon, Aug 08, 2005 at 05:14:45PM +0300, Pekka J Enberg wrote:

                 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 ?