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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Anand Jain <anand.jain@oracle.com>,
        David Sterba <dsterba@suse.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 149/197] btrfs: lift uuid_mutex to callers of btrfs_parse_early_options
Date:   Thu, 13 Sep 2018 15:31:38 +0200
Message-Id: <20180913131847.511999376@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Sterba <dsterba@suse.com>

[ Upstream commit 5139cff598d42b1e531f40c84691a7e945f04553 ]

Prepartory work to fix race between mount and device scan.

btrfs_parse_early_options calls the device scan from mount and we'll
need to let mount completely manage the critical section.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/super.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -892,6 +892,8 @@ static int btrfs_parse_early_options(con
 	char *device_name, *opts, *orig, *p;
 	int error = 0;
 
+	lockdep_assert_held(&uuid_mutex);
+
 	if (!options)
 		return 0;
 
@@ -917,10 +919,8 @@ static int btrfs_parse_early_options(con
 				error = -ENOMEM;
 				goto out;
 			}
-			mutex_lock(&uuid_mutex);
 			error = btrfs_scan_one_device(device_name,
 					flags, holder, fs_devices);
-			mutex_unlock(&uuid_mutex);
 			kfree(device_name);
 			if (error)
 				goto out;
@@ -1528,8 +1528,10 @@ static struct dentry *btrfs_mount_root(s
 	if (!(flags & SB_RDONLY))
 		mode |= FMODE_WRITE;
 
+	mutex_lock(&uuid_mutex);
 	error = btrfs_parse_early_options(data, mode, fs_type,
 					  &fs_devices);
+	mutex_unlock(&uuid_mutex);
 	if (error) {
 		return ERR_PTR(error);
 	}