From fe9ae05cfbe587dda724fcf537c00bc2f287da62 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 8 Mar 2023 11:50:12 +0100 Subject: fbdev: Fix incorrect page mapping clearance at fb_deferred_io_release() 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: Signed-off-by: Takashi Iwai Reviewed-by: Patrik Jakobsson Signed-off-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20230308105012.1845-1-tiwai@suse.de --- include/linux/fb.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/fb.h') diff --git a/include/linux/fb.h b/include/linux/fb.h index 73eb1f85ea8e..05e40fcc7696 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 */ -- cgit