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Subject[PATCH 4.18 145/197] btrfs: extend locked section when adding a new device in device_list_add
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

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

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

[ Upstream commit 9c6d173ea6e4c8c939ae6c257c7fc18f7b320316 ]

Make sure the device_list_lock is held the whole time:

* when the device is being looked up
* new device is initialized and put to the list
* the list counters are updated (fs_devices::opened, fs_devices::total_devices)

Signed-off-by: Anand Jain <anand.jain@oracle.com>
[ update changelog ]
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 | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -765,21 +765,26 @@ static noinline struct btrfs_device *dev
if (IS_ERR(fs_devices))
return ERR_CAST(fs_devices);

+ mutex_lock(&fs_devices->device_list_mutex);
list_add(&fs_devices->fs_list, &fs_uuids);

device = NULL;
} else {
+ mutex_lock(&fs_devices->device_list_mutex);
device = find_device(fs_devices, devid,
disk_super->dev_item.uuid);
}

if (!device) {
- if (fs_devices->opened)
+ if (fs_devices->opened) {
+ mutex_unlock(&fs_devices->device_list_mutex);
return ERR_PTR(-EBUSY);
+ }

device = btrfs_alloc_device(NULL, &devid,
disk_super->dev_item.uuid);
if (IS_ERR(device)) {
+ mutex_unlock(&fs_devices->device_list_mutex);
/* we can safely leave the fs_devices entry around */
return device;
}
@@ -787,14 +792,13 @@ static noinline struct btrfs_device *dev
name = rcu_string_strdup(path, GFP_NOFS);
if (!name) {
btrfs_free_device(device);
+ mutex_unlock(&fs_devices->device_list_mutex);
return ERR_PTR(-ENOMEM);
}
rcu_assign_pointer(device->name, name);

- mutex_lock(&fs_devices->device_list_mutex);
list_add_rcu(&device->dev_list, &fs_devices->devices);
fs_devices->num_devices++;
- mutex_unlock(&fs_devices->device_list_mutex);

device->fs_devices = fs_devices;
*new_device_added = true;
@@ -841,12 +845,15 @@ static noinline struct btrfs_device *dev
* with larger generation number or the last-in if
* generation are equal.
*/
+ mutex_unlock(&fs_devices->device_list_mutex);
return ERR_PTR(-EEXIST);
}

name = rcu_string_strdup(path, GFP_NOFS);
- if (!name)
+ if (!name) {
+ mutex_unlock(&fs_devices->device_list_mutex);
return ERR_PTR(-ENOMEM);
+ }
rcu_string_free(device->name);
rcu_assign_pointer(device->name, name);
if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
@@ -866,6 +873,7 @@ static noinline struct btrfs_device *dev

fs_devices->total_devices = btrfs_super_num_devices(disk_super);

+ mutex_unlock(&fs_devices->device_list_mutex);
return device;
}


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