Hi Am 29.01.23 um 09:28 schrieb Takashi Iwai:
When a fbdev with deferred I/O is once opened and closed, the dirty pages still remain queued in the pageref list, and eventually later those may be processed in the delayed work. This may lead to a corruption of pages, hitting an Oops.
Do you have more information on this problem?The mmap'ed buffer of the fbdev device comes from a vmalloc call. That memory's location never changes; even across pairs of open/close on the device file. I'm surprised that a page entry becomes invalid.
In drm_fbdev_cleanup(), we first remove the fbdefio at [1] and then vfree() the shadow buffer. So the memory should still be around until fbdevio is gone.
[1] https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_fb_helper.c#L2146
This patch makes sure to cancel the delayed work and clean up the pageref list at closing the device for addressing the bug. A part of the cleanup code is factored out as a new helper function that is called from the common fb_release().
The delayed work is required to copy the framebuffer to the device output. So if it's just canceled, could this result in missing updates?
There's a call to cancel_delayed_work_sync() in the new helper fb_deferred_io_release(). Is this the right function? Maybe flush_delayed_work() is a better choice.
Reviewed-by: Patrik Jakobsson <patrik.r.jakobs...@gmail.com> Cc: <sta...@vger.kernel.org> Signed-off-by: Takashi Iwai <ti...@suse.de>
This could use a Fixes tag. It's not exactly clear to me when this problem got originally introduced, but the recent refactoring seems a candidate.
Fixes: 56c134f7f1b5 ("fbdev: Track deferred-I/O pages in pageref struct")
Cc: Thomas Zimmermann <tzimmerm...@suse.de>
Cc: Javier Martinez Canillas <javi...@redhat.com>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Cc: Maxime Ripard <mrip...@kernel.org>
Cc: Zack Rusin <za...@vmware.com>
Cc: VMware Graphics Reviewers <linux-graphics-maintai...@vmware.com>
Cc: Jaya Kumar <jay...@intworks.biz>
Cc: Daniel Vetter <dan...@ffwll.ch>
Cc: "K. Y. Srinivasan" <k...@microsoft.com>
Cc: Haiyang Zhang <haiya...@microsoft.com>
Cc: Wei Liu <wei....@kernel.org>
Cc: Dexuan Cui <de...@microsoft.com>
Cc: Steve Glendinning <steve.glendinn...@shawell.net>
Cc: Bernie Thompson <ber...@plugable.com>
Cc: Helge Deller <del...@gmx.de>
Cc: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Stephen Kitt <st...@sk2.org>
Cc: Peter Suti <peter.s...@streamunlimited.com>
Cc: Sam Ravnborg <s...@ravnborg.org>
Cc: Geert Uytterhoeven <geert+rene...@glider.be>
Cc: ye xingchen <ye.xingc...@zte.com.cn>
Cc: Petr Mladek <pmla...@suse.com>
Cc: John Ogness <john.ogn...@linutronix.de>
Cc: Tom Rix <t...@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fb...@vger.kernel.org
Cc: linux-hyp...@vger.kernel.org
Cc: <sta...@vger.kernel.org> # v5.19+
--- v1->v2: Fix build error without CONFIG_FB_DEFERRED_IO drivers/video/fbdev/core/fb_defio.c | 10 +++++++++- drivers/video/fbdev/core/fbmem.c | 4 ++++ include/linux/fb.h | 1 + 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index c730253ab85c..583cbcf09446 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -313,7 +313,7 @@ void fb_deferred_io_open(struct fb_info *info, } EXPORT_SYMBOL_GPL(fb_deferred_io_open);-void fb_deferred_io_cleanup(struct fb_info *info)+void fb_deferred_io_release(struct fb_info *info) { struct fb_deferred_io *fbdefio = info->fbdefio; struct page *page; @@ -327,6 +327,14 @@ void fb_deferred_io_cleanup(struct fb_info *info) page = fb_deferred_io_page(info, i); page->mapping = NULL; } +} +EXPORT_SYMBOL_GPL(fb_deferred_io_release);
It's all in the same module. No need to export this symbol. Best regards Thomas
+ +void fb_deferred_io_cleanup(struct fb_info *info) +{ + struct fb_deferred_io *fbdefio = info->fbdefio; + + fb_deferred_io_release(info);kvfree(info->pagerefs);mutex_destroy(&fbdefio->lock); diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 3a6c8458eb8d..ab3545a00abc 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1454,6 +1454,10 @@ __releases(&info->lock) struct fb_info * const info = file->private_data;lock_fb_info(info);+#if IS_ENABLED(CONFIG_FB_DEFERRED_IO) + if (info->fbdefio) + fb_deferred_io_release(info); +#endif if (info->fbops->fb_release) info->fbops->fb_release(info,1);
module_put(info->fbops->owner);
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 96b96323e9cb..73eb1f85ea8e 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -662,6 +662,7 @@ extern int 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_release(struct fb_info *info);
extern void fb_deferred_io_cleanup(struct fb_info *info);
extern int fb_deferred_io_fsync(struct file *file, loff_t start,
loff_t end, int datasync);
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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