From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+bhk9baspsj2z0VfhsByFvHYcImW8XuNQcotPJ8klB0dRO128KH3yuaRhQtSPFgYjEMBEx ARC-Seal: i=1; a=rsa-sha256; t=1523473365; cv=none; d=google.com; s=arc-20160816; b=JD9KCBjzp2GjvPj1gE1y95r53IjEPUDtvkhFXvFTV3WUPummEeWaqAmwi5YBPdehX+ 5IDp0SnCkcG3K+JoJtVDD18FkLHdJciAw0b9YipE4tRM9M1QgWiaAzkwANz67YCy7KTM VC0I8kRbh+B/E+Fx3Scs3A2qukV45sC7rs3umhupAWIst2dKizHVEHv1OkBI1/jN8ck9 05M609q8iZlRzLD1wNGvyGn3NKxWmAuo1JVFe6fIi7zmUWQX7vQUpIpPF/jV+ZpQUTsd Ademq0Wh3gzlP+T0H6cpfkyeKxtSG8Tq5LGSRlWDdx1YTTwanrPQ1T703rhaOA9lZ2ZW ZCXQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=52vMf5XS7twpEQu0zUawMN+AYRelibwr78N4FKOnSYc=; b=PdbrqdaUORBpgR7SqA4jeA5ZrInkkkWfiw/EmOidutarB2Y41Rxb/hb43YiKY1EbQ7 GiGD1k5mk2yVevyo+yPVrS6GXMq9WgS8uJdKS5WMsMyYiAyj0t33FE9x29swsSxBwLQG XYkxYSk/zsEAlS//1LkGbAUZVeTS9fgsZIIJWicxJmLSu0sbD4P8BiAnZABnjS1msbdn t9jfLhvjzksAmOmAU1zqgNNp2cApycTDCJNjFEfEVjxfm5ep+ovdPZq2HGU+HYi06lfv 6mP7uNLTe3rNPTcmo/6gEr67ysjj0AIkXC211G5AgcMkx21oY22ZAsQL3mTQ4lpDqzFH IAog== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hannes Reinecke , Ming Lei , James Wang , Jens Axboe , Sasha Levin Subject: [PATCH 4.9 222/310] Fix loop device flush before configure v3 Date: Wed, 11 Apr 2018 20:36:01 +0200 Message-Id: <20180411183632.085674968@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180411183622.305902791@linuxfoundation.org> References: <20180411183622.305902791@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1597476912619997992?= X-GMAIL-MSGID: =?utf-8?q?1597477607458919810?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Wang [ Upstream commit 6460495709aeb651896bc8e5c134b2e4ca7d34a8 ] While installing SLES-12 (based on v4.4), I found that the installer will stall for 60+ seconds during LVM disk scan. The root cause was determined to be the removal of a bound device check in loop_flush() by commit b5dd2f6047ca ("block: loop: improve performance via blk-mq"). Restoring this check, examining ->lo_state as set by loop_set_fd() eliminates the bad behavior. Test method: modprobe loop max_loop=64 dd if=/dev/zero of=disk bs=512 count=200K for((i=0;i<4;i++))do losetup -f disk; done mkfs.ext4 -F /dev/loop0 for((i=0;i<4;i++))do mkdir t$i; mount /dev/loop$i t$i;done for f in `ls /dev/loop[0-9]*|sort`; do \ echo $f; dd if=$f of=/dev/null bs=512 count=1; \ done Test output: stock patched /dev/loop0 18.1217e-05 8.3842e-05 /dev/loop1 6.1114e-05 0.000147979 /dev/loop10 0.414701 0.000116564 /dev/loop11 0.7474 6.7942e-05 /dev/loop12 0.747986 8.9082e-05 /dev/loop13 0.746532 7.4799e-05 /dev/loop14 0.480041 9.3926e-05 /dev/loop15 1.26453 7.2522e-05 Note that from loop10 onward, the device is not mounted, yet the stock kernel consumes several orders of magnitude more wall time than it does for a mounted device. (Thanks for Mike Galbraith , give a changelog review.) Reviewed-by: Hannes Reinecke Reviewed-by: Ming Lei Signed-off-by: James Wang Fixes: b5dd2f6047ca ("block: loop: improve performance via blk-mq") Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/block/loop.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -612,6 +612,9 @@ static int loop_switch(struct loop_devic */ static int loop_flush(struct loop_device *lo) { + /* loop not yet configured, no running thread, nothing to flush */ + if (lo->lo_state != Lo_bound) + return 0; return loop_switch(lo, NULL); }