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SubjectRe: [PATCH] fbdefio: add set_page_dirty handler to deferred IO FB
[correcting stable@]

On Wed, 2008-08-20 at 01:37 -0700, Andrew Morton wrote:
> On Wed, 20 Aug 2008 09:13:23 +0100 Ian Campbell <ijc@hellion.org.uk> wrote:
>
> > Perhaps applying the band-aid at open time instead would be preferred?
>
> That would be less racy, I expect.
[...]
> <tries to write a patch>
>
> OK, seems that fb_ops.fb_open() has no way of getting at the `struct
> file *' which is being opened (wtf?). Screwed. Need to change
> fb_ops.fb_open(), or add a new fb_ops.fb_open_sane().

Ah yes, I remember why I did it in mmap() now...

How about this version? Not as clean as overriding fb_open() but
involves less frobbing with unrelated drivers.

From ae2f7f118518fbfd4006c985b136a5d3d1a314af Mon Sep 17 00:00:00 2001
From: Ian Campbell <ijc@hellion.org.uk>
Date: Wed, 20 Aug 2008 19:54:50 +0100
Subject: [PATCH] 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.

v2: override a_ops at open() time rather than mmap() time to minimise
races per AKPM's concerns.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Acked-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
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: stable@kernel.org [14fcc23fd is in 2.6.25.14 and 2.6.26.1]
---
drivers/video/fb_defio.c | 19 +++++++++++++++++++
drivers/video/fbmem.c | 4 ++++
include/linux/fb.h | 3 +++
3 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 59df132..4835bdc 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -114,6 +114,17 @@ 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;
@@ -163,6 +174,14 @@ void fb_deferred_io_init(struct fb_info *info)
}
EXPORT_SYMBOL_GPL(fb_deferred_io_init);

+void fb_deferred_io_open(struct fb_info *info,
+ struct inode *inode,
+ struct file *file)
+{
+ file->f_mapping->a_ops = &fb_deferred_io_aops;
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_open);
+
void fb_deferred_io_cleanup(struct fb_info *info)
{
void *screen_base = (void __force *) info->screen_base;
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 6b48780..98843c2 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1344,6 +1344,10 @@ fb_open(struct inode *inode, struct file *file)
if (res)
module_put(info->fbops->owner);
}
+#ifdef CONFIG_FB_DEFERRED_IO
+ if (info->fbdefio)
+ fb_deferred_io_open(info, inode, file);
+#endif
out:
unlock_kernel();
return res;
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 3b8870e..531ccd5 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -976,6 +976,9 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,

/* drivers/video/fb_defio.c */
extern void fb_deferred_io_init(struct fb_info *info);
+extern void fb_deferred_io_open(struct fb_info *info,
+ struct inode *inode,
+ struct file *file);
extern void fb_deferred_io_cleanup(struct fb_info *info);
extern int fb_deferred_io_fsync(struct file *file, struct dentry *dentry,
int datasync);
--
1.5.6.3



--
Ian Campbell

Hope that the day after you die is a nice day.
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