Hi,

On Tue, Mar 1, 2011 at 12:35 AM, Robert Święcki [off-list ref] wrote:

quoted

But rather than exporting the notion of restart_addr from memory.c, or
converting to restart_pgoff throughout, simply reset vm_truncate_count
to 0 to force a rescan if mremap move races with preempted truncation.

We have no confirmation that this fixes Robert's BUG,
but it is a fix that's worth making anyway.

Hi, I don't have currently access to my rs232/console testing machine
(lame excuse but it helps a lot;), cause I'm working currently OOtO,
so I'll try to test it asap - which is probably Mar 15th or so.

So, I compiled 2.6.38 and started fuzzing it. I'm bumping into other
problems, and never seen anything about mremap in 2.6.38 (yet), as it
had been happening in 2.6.37-rc2. The output goes to
http://alt.swiecki.net/linux_kernel/ - I'm still trying.

Btw, the fuzzer is here: http://code.google.com/p/iknowthis/

I think i was trying it with this revision:
http://code.google.com/p/iknowthis/source/detail?r=11 (i386 mode,
newest 'iknowthis' supports x86-64 natively), so feel free to try it.

It used to crash the machine (it's BUG_ON but the system became
unusable) in matter of hours. Btw, when I was testing it for the last
time it Ooopsed much more frequently in proc_readdir (I sent report in
one of earliet e-mails).

quoted

Signed-off-by: Hugh Dickins <hughd@google.com>
---

 mm/mremap.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- 2.6.38-rc6/mm/mremap.c      2011-01-18 22:04:56.000000000 -0800
+++ linux/mm/mremap.c   2011-02-23 15:29:52.000000000 -0800

@@ -94,9 +94,7 @@ static void move_ptes(struct vm_area_str

                */
               mapping = vma->vm_file->f_mapping;
               spin_lock(&mapping->i_mmap_lock);
-               if (new_vma->vm_truncate_count &&
-                   new_vma->vm_truncate_count != vma->vm_truncate_count)
-                       new_vma->vm_truncate_count = 0;
+               new_vma->vm_truncate_count = 0;
       }

       /*

--
Robert Święcki

-- 
Robert Święcki

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