acting on all tasks mapping a dirty page

["Brian Lindahl" <Brian.Lindahl@SpaceDev.com>]

Given a dirty physical page, I need to perform a certain action on each process (task) that maps to it. To do this, I mark each 'mm' by tracing the list of vma's in the page's mapping. I later iterate over the task list and perform an action on each 'mm' that is marked. Because each task has it's own pte, I think I have to scan the vma list for a mapping twice.

/* locks ignored for brevity, assume atomic */

struct page * page; /* = some page */
int pte_dirty = 0;

vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
  pte_dirty; /* = via page_check_address, is the pte dirty? */

if (pte_dirty)
  vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
    mark(vma->vm_mm);

struct task_struct * task; /* = task_list */
for(; task; task = task->next_task)
  if (task->mm->marked)
    do_action(task);

Is there a better way to do this? Less importantly, is there a way to avoid two vma_prio_tree_foreach's? I didn't want to assume that the pte reference is identical for all mappings for any given page, but it looks that way. If this is true, then I can simply scan it once and use the result from the examination of pte dirty on the first vma (rather, it's owning mm)?

Thanks!

Brian Lindahl 
Embedded Software Engineer 
858-375-2077 
brian.lindahl@spacedev.com 
SpaceDev, Inc. 
"We Make Space Happen"
 
 
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