linux-kernel - [PATCH 4.18 150/197] btrfs: reorder initialization before the mount locks uuid

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Date:   Thu, 13 Sep 2018 15:31:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Anand Jain <anand.jain@...cle.com>,
        David Sterba <dsterba@...e.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 150/197] btrfs: reorder initialization before the mount locks uuid_mutex

4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: David Sterba <dsterba@...e.com>

[ Upstream commit 399f7f4c42e8a58c8456264d5112287aefe44cf4 ]

In preparation to take a big lock, move resource initialization before
the critical section. It's not obvious from the diff, the desired order
is:

- initialize mount security options
- allocate temporary fs_info
- allocate superblock buffers

Reviewed-by: Anand Jain <anand.jain@...cle.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/super.c |   30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1528,14 +1528,6 @@ 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);
-	}
-
 	security_init_mnt_opts(&new_sec_opts);
 	if (data) {
 		error = parse_security_options(data, &new_sec_opts);
@@ -1543,12 +1535,6 @@ static struct dentry *btrfs_mount_root(s
 			return ERR_PTR(error);
 	}
 
-	mutex_lock(&uuid_mutex);
-	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
-	mutex_unlock(&uuid_mutex);
-	if (error)
-		goto error_sec_opts;
-
 	/*
 	 * Setup a dummy root and fs_info for test/set super.  This is because
 	 * we don't actually fill this stuff out until open_ctree, but we need
@@ -1561,8 +1547,6 @@ static struct dentry *btrfs_mount_root(s
 		goto error_sec_opts;
 	}
 
-	fs_info->fs_devices = fs_devices;
-
 	fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
 	fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
 	security_init_mnt_opts(&fs_info->security_opts);
@@ -1572,6 +1556,20 @@ static struct dentry *btrfs_mount_root(s
 	}
 
 	mutex_lock(&uuid_mutex);
+	error = btrfs_parse_early_options(data, mode, fs_type, &fs_devices);
+	mutex_unlock(&uuid_mutex);
+	if (error)
+		goto error_fs_info;
+
+	mutex_lock(&uuid_mutex);
+	error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
+	mutex_unlock(&uuid_mutex);
+	if (error)
+		goto error_fs_info;
+
+	fs_info->fs_devices = fs_devices;
+
+	mutex_lock(&uuid_mutex);
 	error = btrfs_open_devices(fs_devices, mode, fs_type);
 	mutex_unlock(&uuid_mutex);
 	if (error)