The recent fix for the deferred I/O by the commit
3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices")
caused a regression when the same fb device is opened/closed while
it's being used. It resulted in a frozen screen even if something
is redrawn there after the close. The breakage is because the patch
was made under a wrong assumption of a single open; in the current
code, fb_deferred_io_release() cleans up the page mapping of the
pageref list and it calls cancel_delayed_work_sync() unconditionally,
where both are no correct behavior for multiple opens.
This patch adds a refcount for the opens of the device, and applies
the cleanup only when all files get closed.
As both fb_deferred_io_open() and _close() are called always in the
fb_info lock (mutex), it's safe to use the normal int for the
refcounting.
Also, a useless BUG_ON() is dropped.
Fixes: 3efc61d95259 ("fbdev: Fix invalid page access after closing deferred I/O devices")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
v1->v2:
* Rename to fb_deferred_io_lastclose()
* Rename the new field from opens to open_count
* Removed unused variable
* More comments about fb_info locking
drivers/video/fbdev/core/fb_defio.c | 17 +++++++++++++----
include/linux/fb.h | 1 +
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index aa5f059d0222..274f5d0fa247 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -305,17 +305,18 @@ void fb_deferred_io_open(struct fb_info *info,
struct inode *inode,
struct file *file)
{
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
file->f_mapping->a_ops = &fb_deferred_io_aops;
+ fbdefio->open_count++;
}
EXPORT_SYMBOL_GPL(fb_deferred_io_open);
-void fb_deferred_io_release(struct fb_info *info)
+static void fb_deferred_io_lastclose(struct fb_info *info)
{
- struct fb_deferred_io *fbdefio = info->fbdefio;
struct page *page;
int i;
- BUG_ON(!fbdefio);
cancel_delayed_work_sync(&info->deferred_work);
/* clear out the mapping that we setup */
@@ -324,13 +325,21 @@ void fb_deferred_io_release(struct fb_info *info)
page->mapping = NULL;
}
}
+
+void fb_deferred_io_release(struct fb_info *info)
+{
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
+ if (!--fbdefio->open_count)
+ fb_deferred_io_lastclose(info);
+}
EXPORT_SYMBOL_GPL(fb_deferred_io_release);
void fb_deferred_io_cleanup(struct fb_info *info)
{
struct fb_deferred_io *fbdefio = info->fbdefio;
- fb_deferred_io_release(info);
+ fb_deferred_io_lastclose(info);
kvfree(info->pagerefs);
mutex_destroy(&fbdefio->lock);
diff --git a/include/linux/fb.h b/include/linux/fb.h
index d8d20514ea05..02d09cb57f6c 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -212,6 +212,7 @@ struct fb_deferred_io {
/* delay between mkwrite and deferred handler */
unsigned long delay;
bool sort_pagereflist; /* sort pagelist by offset */
+ int open_count; /* number of opened files; protected by fb_info lock */
struct mutex lock; /* mutex that protects the pageref list */
struct list_head pagereflist; /* list of pagerefs for touched pages */
/* callback */
--
2.35.3
