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 1C772395266; Tue, 21 Jul 2026 18:13:47 +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=1784657628; cv=none; b=gCgzlD7e8ZLeHu71QSdRSygxEXACaGEuJgCDZrTPZLJnJvKbSek2ll30BiXXdCR0MX4bItiuv72V4ruPU/OKEiryb3ZuitrFqr20EOJse4tw5nWmzepwisDhuie+PjjdRaDAsUPpQ+NYikM6l/ToqlgmuMz45yIgqRdgmLX3FL4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657628; c=relaxed/simple; bh=i2b3yEf+HUJ6hxfXjg39fdpC/MBGgAhr9EC7eGxNNFQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iaVcKy+DmsRU5jRGY9yH0KucOnwZTqIwKEyJLcr6+VNRGto5eP15DtyZl4aKT7dFpYWW9ZeaomCyKxv1u+gu36RuPpFnVOPRn8vJQztw9d4ddT0kDWykLJGEiLnI0Su3COfuBX43SQ9mtdZ894UzoE5Wtx1KdgkP5PEr7TVCSAw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VAg57vzy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VAg57vzy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81F831F000E9; Tue, 21 Jul 2026 18:13:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784657627; bh=T2utB6hds3wKcJr6cukotDQ8NcdxIg7fP7TjR4Iw74o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VAg57vzysgmkkwyZq67IjWYAIemEmYt2uUQfMRTnnUZz+vmy+9urJ7blcnpA9qQxv qnEg8Kg30ytE6zIR5rRLywuQvNr9Os44wwkt5Xo9PQK6viM8DL34xBoKYUp2X8w9Xx f4LKGAuC6KtlGX9yYPkjYV3f3N73XLeDYaoTS1uQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Abd-Alrhman Masalkhi , Yu Kuai , Sasha Levin Subject: [PATCH 6.18 0834/1611] md/raid1: honor REQ_NOWAIT when waiting for behind writes Date: Tue, 21 Jul 2026 17:15:50 +0200 Message-ID: <20260721152534.148689132@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Abd-Alrhman Masalkhi [ Upstream commit a286cb88ddb26c5f4377859d8e77233d9181eb82 ] raid1 supports REQ_NOWAIT reads by avoiding waits in the barrier path through wait_read_barrier(). However, a read can still block on a WriteMostly device when the array uses a bitmap and there are outstanding behind writes. In that case raid1 unconditionally calls wait_behind_writes(), which may sleep until all behind writes complete. As a result, a REQ_NOWAIT read can block despite the caller explicitly requesting non-blocking behavior. This ensures that raid1 consistently honors REQ_NOWAIT reads across all paths that may otherwise wait for behind writes. Fixes: 5aa705039c4f ("md: raid1 add nowait support") Signed-off-by: Abd-Alrhman Masalkhi Link: https://patch.msgid.link/20260611083514.754922-1-abd.masalkhi@gmail.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin --- drivers/md/md-bitmap.c | 9 +++++++-- drivers/md/md-bitmap.h | 2 +- drivers/md/md-llbitmap.c | 13 ++++++++----- drivers/md/md.c | 2 +- drivers/md/raid1.c | 10 +++++++--- 5 files changed, 24 insertions(+), 12 deletions(-) diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c index 1edccebb2130de..2a958407829274 100644 --- a/drivers/md/md-bitmap.c +++ b/drivers/md/md-bitmap.c @@ -2064,18 +2064,23 @@ static void bitmap_end_behind_write(struct mddev *mddev) bitmap->mddev->bitmap_info.max_write_behind); } -static void bitmap_wait_behind_writes(struct mddev *mddev) +static bool bitmap_wait_behind_writes(struct mddev *mddev, bool nowait) { struct bitmap *bitmap = mddev->bitmap; /* wait for behind writes to complete */ if (bitmap && atomic_read(&bitmap->behind_writes) > 0) { + if (nowait) + return false; + pr_debug("md:%s: behind writes in progress - waiting to stop.\n", mdname(mddev)); /* need to kick something here to make sure I/O goes? */ wait_event(bitmap->behind_wait, atomic_read(&bitmap->behind_writes) == 0); } + + return true; } static void bitmap_destroy(struct mddev *mddev) @@ -2085,7 +2090,7 @@ static void bitmap_destroy(struct mddev *mddev) if (!bitmap) /* there was no bitmap */ return; - bitmap_wait_behind_writes(mddev); + bitmap_wait_behind_writes(mddev, false); if (!test_bit(MD_SERIALIZE_POLICY, &mddev->flags)) mddev_destroy_serial_pool(mddev, NULL); diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h index 214f623c7e790b..f46674bdfeb918 100644 --- a/drivers/md/md-bitmap.h +++ b/drivers/md/md-bitmap.h @@ -98,7 +98,7 @@ struct bitmap_operations { void (*start_behind_write)(struct mddev *mddev); void (*end_behind_write)(struct mddev *mddev); - void (*wait_behind_writes)(struct mddev *mddev); + bool (*wait_behind_writes)(struct mddev *mddev, bool nowait); md_bitmap_fn *start_write; md_bitmap_fn *end_write; diff --git a/drivers/md/md-llbitmap.c b/drivers/md/md-llbitmap.c index 50eeddf7f539ba..dc9b72494a81ae 100644 --- a/drivers/md/md-llbitmap.c +++ b/drivers/md/md-llbitmap.c @@ -1432,16 +1432,19 @@ static void llbitmap_end_behind_write(struct mddev *mddev) wake_up(&llbitmap->behind_wait); } -static void llbitmap_wait_behind_writes(struct mddev *mddev) +static bool llbitmap_wait_behind_writes(struct mddev *mddev, bool nowait) { struct llbitmap *llbitmap = mddev->bitmap; - if (!llbitmap) - return; + if (llbitmap && atomic_read(&llbitmap->behind_writes) > 0) { + if (nowait) + return false; - wait_event(llbitmap->behind_wait, - atomic_read(&llbitmap->behind_writes) == 0); + wait_event(llbitmap->behind_wait, + atomic_read(&llbitmap->behind_writes) == 0); + } + return true; } static ssize_t bits_show(struct mddev *mddev, char *page) diff --git a/drivers/md/md.c b/drivers/md/md.c index 7675246fa8e984..0d60c211e7c083 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6928,7 +6928,7 @@ EXPORT_SYMBOL_GPL(md_stop_writes); static void mddev_detach(struct mddev *mddev) { if (md_bitmap_enabled(mddev, false)) - mddev->bitmap_ops->wait_behind_writes(mddev); + mddev->bitmap_ops->wait_behind_writes(mddev, false); if (mddev->pers && mddev->pers->quiesce && !is_md_suspended(mddev)) { mddev->pers->quiesce(mddev, 1); mddev->pers->quiesce(mddev, 0); diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 6f2f065252e8c9..cc057ef1829ac1 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -1319,6 +1319,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio, int max_sectors; int rdisk; bool r1bio_existed = !!r1_bio; + bool nowait = bio->bi_opf & REQ_NOWAIT; /* * If r1_bio is set, we are blocking the raid1d thread @@ -1331,8 +1332,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio, * Still need barrier for READ in case that whole * array is frozen. */ - if (!wait_read_barrier(conf, bio->bi_iter.bi_sector, - bio->bi_opf & REQ_NOWAIT)) { + if (!wait_read_barrier(conf, bio->bi_iter.bi_sector, nowait)) { bio_wouldblock_error(bio); return; } @@ -1373,7 +1373,11 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio, * over-take any writes that are 'behind' */ mddev_add_trace_msg(mddev, "raid1 wait behind writes"); - mddev->bitmap_ops->wait_behind_writes(mddev); + if (!mddev->bitmap_ops->wait_behind_writes(mddev, nowait)) { + bio_wouldblock_error(bio); + set_bit(R1BIO_Returned, &r1_bio->state); + goto err_handle; + } } if (max_sectors < bio_sectors(bio)) { -- 2.53.0