Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Fri, 27 Jun 2003 11:13:19 -0500 | From | Dave McCracken <> | Subject | [PATCH 2.5.73-mm1] Make sure truncate fix has no race |
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Paul McKenney pointed out that reading the truncate sequence number in do_no_page might not be entirely safe if the ->nopage callout takes no locks. The simple solution is to move the read before the unlock of page_table_lock. Here's a patch that does it.
Dave McCracken
====================================================================== Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059 dmccr@us.ibm.com T/L 678-3059 --- 2.5.73-mm1/mm/memory.c 2003-06-27 10:40:48.000000000 -0500 +++ 2.5.73-mm1-trunc/mm/memory.c 2003-06-27 10:47:10.000000000 -0500 @@ -1402,11 +1402,11 @@ do_no_page(struct mm_struct *mm, struct return do_anonymous_page(mm, vma, page_table, pmd, write_access, address); pte_unmap(page_table); - spin_unlock(&mm->page_table_lock); mapping = vma->vm_file->f_dentry->d_inode->i_mapping; -retry: sequence = atomic_read(&mapping->truncate_count); + spin_unlock(&mm->page_table_lock); +retry: new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0); /* no page was available -- either SIGBUS or OOM */ @@ -1441,6 +1441,7 @@ retry: * retry getting the page. */ if (unlikely(sequence != atomic_read(&mapping->truncate_count))) { + sequence = atomic_read(&mapping->truncate_count); spin_unlock(&mm->page_table_lock); page_cache_release(new_page); goto retry;
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