From mboxrd@z Thu Jan 1 00:00:00 1970 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 Message-ID: <69440000.1056730399@baldur.austin.ibm.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="==========1873729384==========" Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Linux Memory Management , Linux Kernel List-ID: --==========1873729384========== Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline 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 --==========1873729384========== Content-Type: text/plain; charset=us-ascii; name="trunc-2.5.73-mm1-1.diff" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="trunc-2.5.73-mm1-1.diff"; size=897 --- 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; --==========1873729384==========-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org