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Subject[PATCH 4.18 139/197] btrfs: lift uuid_mutex to callers of btrfs_open_devices
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: David Sterba <dsterba@suse.com>

[ Upstream commit f5194e34cabaddd348a90f950e0a8188dd26cdc0 ]

Prepartory work to fix race between mount and device scan.

The callers will have to manage the critical section, eg. mount wants to
scan and then call btrfs_open_devices without the ioctl scan walking in
and modifying the fs devices in the meantime.

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 | 2 ++
fs/btrfs/volumes.c | 4 ++--
2 files changed, 4 insertions(+), 2 deletions(-)

--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1565,7 +1565,9 @@ static struct dentry *btrfs_mount_root(s
goto error_fs_info;
}

+ mutex_lock(&uuid_mutex);
error = btrfs_open_devices(fs_devices, mode, fs_type);
+ mutex_unlock(&uuid_mutex);
if (error)
goto error_fs_info;

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1146,7 +1146,8 @@ int btrfs_open_devices(struct btrfs_fs_d
{
int ret;

- mutex_lock(&uuid_mutex);
+ lockdep_assert_held(&uuid_mutex);
+
mutex_lock(&fs_devices->device_list_mutex);
if (fs_devices->opened) {
fs_devices->opened++;
@@ -1156,7 +1157,6 @@ int btrfs_open_devices(struct btrfs_fs_d
ret = open_fs_devices(fs_devices, flags, holder);
}
mutex_unlock(&fs_devices->device_list_mutex);
- mutex_unlock(&uuid_mutex);

return ret;
}

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