From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5D1B43D1A8E for ; Sat, 10 Oct 2026 06:55:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791615353; cv=none; b=pwcXhATcJ2kotOkJYekiIGEIf9fqSJgcEVAxkERYyPy4+ZsGwpPfsZYJqaB/P+keq43wlevEaXeR769GbZ7d9yw2NZIwI4cqX8wyQFZaoMhtosCSnZ47lfCK7JvdXuWJ1p/JsaK5GGLMIPmKGplmZy27auh+K6yKfsB3qHa8F74= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791615353; c=relaxed/simple; bh=46pdqWWWiOsJ5zguAHSYvDLWrSpcqWMhxDddkipq130=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=hNLFKEJejz8IDN9hHkK9occaHWT+V97qni5sA+7XvzpFKmBtI8k2hxytJc6/TaOBTrLSMqFamjKzPg/34Pt4YljBCvwBTUaw72xINu6JeYm/8OH8W3cVmkZwUaVZVYzZxWoZmU1B9lVgKZLysSUzxNOhbXsAo/bfntFnrA2Pxl8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OH80fbb7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OH80fbb7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB5C91F000FF; Sat, 10 Oct 2026 06:55:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791615351; bh=QRWnPGtWKckNp3hs8edix9eHlTIjDYrtAUIeCheZUps=; h=From:To:Cc:Subject:Date; b=OH80fbb7FijIsySrCttb8hNTS0py1Tro1H3JnuxrFmx6UbThO+JXzIiQfsKTusWFR a0rkAQXZbpoQagFC2GpYv4ZulK6+YIpEDCCJPm6VSLGYXrExGljrmqmT49ot2SynbO 9JWskV+pdL3psv0K1YBQjMlKqVV4pHhiLLK9PKbmIqJc/i6yMq0qZgdUHHW0CShS3a V3Vwuw1ss9y5W/THs75nt7GrwV2wjSarT7MjdCrx5XcBwBVWd61y8RRFDZ6/PbtjmF FyByD0FJbS5FUxLPSfHZDPbR2WBceWcdA+r6ZWHeDOu3P5uv48APr6GIAx2XFT5Jxo 5ObqeGhvZ5V0w== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , stable@kernel.org Subject: [PATCH 1/2] f2fs: fix to use bio_in_atomic() in f2fs_write_end_io() Date: Sat, 10 Oct 2026 14:55:45 +0800 Message-ID: <20261010065546.1762091-1-chao@kernel.org> X-Mailer: git-send-email 2.56.0.385.gd3acb90ef8-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chao Yu f2fs_write_end_io() uses in_atomic() to decide whether a write bio which exceeds max_atc_write_bio_size or max_atc_write_bio_entry_cnt should be completed in sbi->wq rather than in the current context. However, in_atomic() is not meant to be used outside core kernel code (checkpatch.pl warns about it), as it only looks at preempt_count(): it misses irqs-disabled and RCU read-side critical sections, and on kernels without CONFIG_PREEMPT_COUNT it cannot see spinlock-held sections at all. In those contexts, a large write bio will still be completed inline, which defeats the purpose of the above knobs. The block layer provides bio_in_atomic() for exactly this purpose, it checks rcu_preempt_depth() and preemptible(), and conservatively returns true if CONFIG_PREEMPT_COUNT is disabled, let's use it instead. The difference is as below: Context | in_atomic() | bio_in_atomic() -------------------------------------+----------------+---------------- Hard IRQ / softirq | true | true IRQs disabled, preempt count 0 | false (missed) | true RCU read lock (CONFIG_PREEMPTION) | false (missed) | true Kernel w/o CONFIG_PREEMPT_COUNT | IRQ ctx only | always true Note that on kernels without CONFIG_PREEMPT_COUNT, write bios exceeding the thresholds will always be offloaded to sbi->wq, since there is no way to tell whether the current context is atomic. The thresholds default to UINT_MAX, so the default behavior is not changed. Cc: stable@kernel.org Fixes: 3de6b8094115 ("f2fs: Run f2fs_write_end_io() asynchronously") Signed-off-by: Chao Yu --- fs/f2fs/data.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 2613e8821af6..86150f7a372c 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -398,8 +398,9 @@ static void f2fs_write_end_io(struct bio *bio) sbi = bio->bi_private; - if (in_atomic() && (bio->bi_iter.bi_size > sbi->max_atc_write_bio_size || - F2FS_BIO(bio)->entry_cnt > sbi->max_atc_write_bio_entry_cnt)) { + if (bio_in_atomic() && + (bio->bi_iter.bi_size > sbi->max_atc_write_bio_size || + F2FS_BIO(bio)->entry_cnt > sbi->max_atc_write_bio_entry_cnt)) { struct work_struct *w; w = &container_of(bio, struct f2fs_bio, bio)->work; -- 2.49.0