From patchwork Mon Dec 18 09:57:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nam Cao X-Patchwork-Id: 13496504 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B925125A7; Mon, 18 Dec 2023 09:57:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="QYB7/wZC"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="2c6pIzvC" From: Nam Cao DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1702893460; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=m8g1705acTr/tgoPBJPCxDzSYFLliwXwTit5yL2vhLY=; b=QYB7/wZCAy3GKkvWhPXPJbjtv5jqKhrH0IhYndaJGvRnNE5S1hUB61ByPMusRDvNNvXgM2 Q42MtKtQcxIyvDOHEYF2bCyRS3fRHM1KxPYBheyoHag0Q60sHOgHrQe4WBs4L4E4anC+yZ XqiLqjsIHSNwrd5uf/LED1uVcwDCIqsepv6Tq0iX/+/+w5S6Ew9QTde2vjoYJDeY+j6Tjs 9VL/bFO4UEd87V4BsklZqXav85aVZRZpD1ecWcON3F/ygKc/m7ezm5g0C7R0qmcFXlFlK/ RYNSGG5Ff4hjhg06dbm+Df+XIta8gHP6ifJnPlez0yxhdqzWqMKtqAyhV/b1qg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1702893460; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=m8g1705acTr/tgoPBJPCxDzSYFLliwXwTit5yL2vhLY=; b=2c6pIzvCC2pWWiknD+IJ9Ed+Cd9zmCRkfZrO1U/2cAVRfSf59hAhENuaciIIH6Edz/mnb5 Z7ATSmsGmX1ghRCA== To: Jaya Kumar , Daniel Vetter , Helge Deller , Antonino Daplas , Andrew Morton , Paul Mundt , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: bigeasy@linutronix.de, Nam Cao , stable@vger.kernel.org Subject: [PATCH 1/2] fb: flush deferred work in fb_deferred_io_fsync() Date: Mon, 18 Dec 2023 10:57:30 +0100 Message-Id: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The driver's fsync() is supposed to flush any pending operation to hardware. It is implemented in this driver by cancelling the queued deferred IO first, then schedule it for "immediate execution" by calling schedule_delayed_work() again with delay=0. However, setting delay=0 only means the work is scheduled immediately, it does not mean the work is executed immediately. There is no guarantee that the work is finished after schedule_delayed_work() returns. After this driver's fsync() returns, there can still be pending work. Furthermore, if close() is called by users immediately after fsync(), the pending work gets cancelled and fsync() may do nothing. To ensure that the deferred IO completes, use flush_delayed_work() instead. Write operations to this driver either write to the device directly, or invoke schedule_delayed_work(); so by flushing the workqueue, it can be guaranteed that all previous writes make it to the device. Fixes: 5e841b88d23d ("fb: fsync() method for deferred I/O flush.") Cc: stable@vger.kernel.org Signed-off-by: Nam Cao Reviewed-by: Sebastian Andrzej Siewior --- drivers/video/fbdev/core/fb_defio.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index 274f5d0fa247..6c8b81c452f0 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -132,11 +132,7 @@ int fb_deferred_io_fsync(struct file *file, loff_t start, loff_t end, int datasy return 0; inode_lock(inode); - /* Kill off the delayed work */ - cancel_delayed_work_sync(&info->deferred_work); - - /* Run it immediately */ - schedule_delayed_work(&info->deferred_work, 0); + flush_delayed_work(&info->deferred_work); inode_unlock(inode); return 0; From patchwork Mon Dec 18 09:57:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nam Cao X-Patchwork-Id: 13496505 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B96F125AD; Mon, 18 Dec 2023 09:57:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Kkxi3zSo"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="faqY/3zT" From: Nam Cao DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1702893461; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VQgbUD/9nx5mi5GS7bnC72VqZMbKoUb8rPJa0pNUbQg=; b=Kkxi3zSonUFc6y94k8nGCK8agXTv2WfFgXRqzSp3Kk+EiUi7x+4dK3FUjlcRqGkqKnqrdG kb8BZYzCINHtS1fVRyZf7x+513wa1htBnuxQmfHW+ipRyBldeMol/tQQjK6WMkAxuB3x6K x8B+X5gwp697Y88VxGi60b4L/rUbzzD+8ILa8C+86UpcVy922Z+CjbUOPVqhCRDMcCDu0I 6H4/oeqWUo/2lr6tyNgT+jEndcAWIYt4FDNOfX3cSQKyo5trqc6JMZGTffcRRBnajXkN4r estX+xLS1zqN2YQaL4H1thIpODq6P2R9DzFsGaaBWsuXXA+2hNhFi/W0S98fWw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1702893461; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VQgbUD/9nx5mi5GS7bnC72VqZMbKoUb8rPJa0pNUbQg=; b=faqY/3zT2f1RnxKjUVyMNBjYHnbagbsIJ2OtxRfsf+0e6/fXqcPT1MzTJJJRoZZvDJzJid B41FU8hSdvRtjnAA== To: Jaya Kumar , Daniel Vetter , Helge Deller , Antonino Daplas , Andrew Morton , Paul Mundt , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: bigeasy@linutronix.de, Nam Cao , stable@vger.kernel.org Subject: [PATCH 2/2] fb: flush deferred IO before closing Date: Mon, 18 Dec 2023 10:57:31 +0100 Message-Id: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 When framebuffer gets closed, the queued deferred IO gets cancelled. This can cause some last display data to vanish. This is problematic for users who send a still image to the framebuffer, then close the file: the image may never appear. To ensure none of display data get lost, flush the queued deferred IO first before closing. Another possible solution is to delete the cancel_delayed_work_sync() instead. The difference is that the display may appear some time after closing. However, the clearing of page mapping after this needs to be removed too, because the page mapping is used by the deferred work. It is not completely obvious whether it is okay to not clear the page mapping. For a patch intended for stable trees, go with the simple and obvious solution. Fixes: 60b59beafba8 ("fbdev: mm: Deferred IO support") Cc: stable@vger.kernel.org Signed-off-by: Nam Cao Reviewed-by: Sebastian Andrzej Siewior --- drivers/video/fbdev/core/fb_defio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index 6c8b81c452f0..1ae1d35a5942 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c @@ -313,7 +313,7 @@ static void fb_deferred_io_lastclose(struct fb_info *info) struct page *page; int i; - cancel_delayed_work_sync(&info->deferred_work); + flush_delayed_work(&info->deferred_work); /* clear out the mapping that we setup */ for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {