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Subject[PATCH 4.18 147/197] btrfs: use device_list_mutex when removing stale devices
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4.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Anand Jain <anand.jain@oracle.com>

[ Upstream commit 7bcb8164ad9435068d9bc3b83b8a002c64d63ff6 ]

btrfs_free_stale_devices() finds a stale (not opened) device matching
path in the fs_uuid list. We are already under uuid_mutex so when we
check for each fs_devices, hold the device_list_mutex too.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.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/volumes.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -640,8 +640,11 @@ static void btrfs_free_stale_devices(con
struct btrfs_device *device, *tmp_device;

list_for_each_entry_safe(fs_devices, tmp_fs_devices, &fs_uuids, fs_list) {
- if (fs_devices->opened)
+ mutex_lock(&fs_devices->device_list_mutex);
+ if (fs_devices->opened) {
+ mutex_unlock(&fs_devices->device_list_mutex);
continue;
+ }

list_for_each_entry_safe(device, tmp_device,
&fs_devices->devices, dev_list) {
@@ -661,16 +664,18 @@ static void btrfs_free_stale_devices(con
continue;

/* delete the stale device */
- if (fs_devices->num_devices == 1) {
- btrfs_sysfs_remove_fsid(fs_devices);
- list_del(&fs_devices->fs_list);
- free_fs_devices(fs_devices);
+ fs_devices->num_devices--;
+ list_del(&device->dev_list);
+ btrfs_free_device(device);
+
+ if (fs_devices->num_devices == 0)
break;
- } else {
- fs_devices->num_devices--;
- list_del(&device->dev_list);
- btrfs_free_device(device);
- }
+ }
+ mutex_unlock(&fs_devices->device_list_mutex);
+ if (fs_devices->num_devices == 0) {
+ btrfs_sysfs_remove_fsid(fs_devices);
+ list_del(&fs_devices->fs_list);
+ free_fs_devices(fs_devices);
}
}
}

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