From: Takashi Iwai tiwai@suse.de
commit fe9ae05cfbe587dda724fcf537c00bc2f287da62 upstream.
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@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de Reviewed-by: Patrik Jakobsson patrik.r.jakobsson@gmail.com Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/20230308105012.1845-1-tiwai@su... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/video/fbdev/core/fb_defio.c | 17 +++++++++++++---- include/linux/fb.h | 1 + 2 files changed, 14 insertions(+), 4 deletions(-)
--- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -309,17 +309,18 @@ void fb_deferred_io_open(struct fb_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 */ @@ -328,13 +329,21 @@ void fb_deferred_io_release(struct fb_in 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); --- 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 */