Re: kernel BUG at lib/radix-tree.c:473!

[Ian Campbell <ijc@hellion.org.uk>]

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On Mon, 2008-08-18 at 11:32 +1000, Nick Piggin wrote:
> On Monday 18 August 2008 02:19, Ian Campbell wrote:
> > FWIW the patch below apparently makes it work for me, but I'm not going
> > to pretend I follow what's going on, why or what else it breaks ;-)
> 
> I think Iwould prefer fs_defio to use its own set_page_dirty
> function. __set_page_dirty_no_writeback is supposed to be used
> on pagecache, by filesystems.

fbdefio: add set_page_dirty handler to deferred IO FB

Fixes kernel BUG at lib/radix-tree.c:473.

Previously the handler was incidentally provided by tmpfs but this was
removed with:

  commit 14fcc23fdc78e9d32372553ccf21758a9bd56fa1
  Author: Hugh Dickins <hugh@veritas.com>
  Date:   Mon Jul 28 15:46:19 2008 -0700

    tmpfs: fix kernel BUG in shmem_delete_inode

relying on this behaviour was incorrect in any case and the BUG
also appeared when the device node was on an ext3 filesystem.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Johannes Weiner <hannes@saeurebad.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Kel Modderman <kel@otaku42.de>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 drivers/video/fb_defio.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 59df132..214bb7c 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -114,11 +114,23 @@ static struct vm_operations_struct
fb_deferred_io_vm_ops = {
 	.page_mkwrite	= fb_deferred_io_mkwrite,
 };
 
+static int fb_deferred_io_set_page_dirty(struct page *page)
+{
+	if (!PageDirty(page))
+		SetPageDirty(page);
+	return 0;
+}
+
+static const struct address_space_operations fb_deferred_io_aops = {
+	.set_page_dirty = fb_deferred_io_set_page_dirty,
+};
+
 static int fb_deferred_io_mmap(struct fb_info *info, struct
vm_area_struct *vma)
 {
 	vma->vm_ops = &fb_deferred_io_vm_ops;
 	vma->vm_flags |= ( VM_IO | VM_RESERVED | VM_DONTEXPAND );
 	vma->vm_private_data = info;
+	vma->vm_file->f_mapping->a_ops = &fb_deferred_io_aops;
 	return 0;
 }
 
-- 
1.5.6.3

-- 
Ian Campbell

How many Unix hacks does it take to change a light bulb?
   Let's see, can you use a shell script for that or does it need a C program?

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