On Thu, Apr 12, 2018 at 10:29:35AM +0800, Anand Jain wrote:
> close_fs_devices() closes devices of a given fsid, and it is limited
> to all the devices of a fsid, so we don't have to hold the global
> uuid_mutex, instead we need the device_list_mutex as the device state is
> being changed.
>
> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
> ---
> fs/btrfs/volumes.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index dfebf8f29916..4c29214e0c18 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -995,7 +995,6 @@ static void btrfs_prepare_close_one_device(struct btrfs_device *device)
> device->uuid);
> BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
>
> - /* Safe because we are under uuid_mutex */
> if (device->name) {
> name = rcu_string_strdup(device->name->str, GFP_NOFS);
> BUG_ON(!name); /* -ENOMEM */
> @@ -1013,10 +1012,12 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
>
> INIT_LIST_HEAD(&pending_put);
>
> - if (--fs_devices->opened > 0)
> + mutex_lock(&fs_devices->device_list_mutex);
> + if (--fs_devices->opened > 0) {
> + mutex_unlock(&fs_devices->device_list_mutex);
> return 0;
> + }
>
> - mutex_lock(&fs_devices->device_list_mutex);
> list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
> btrfs_prepare_close_one_device(device);
> list_add(&device->dev_list, &pending_put);
> @@ -1050,13 +1051,11 @@ int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
> struct btrfs_fs_devices *seed_devices = NULL;
> int ret;
>
> - mutex_lock(&uuid_mutex);
> ret = close_fs_devices(fs_devices);
> if (!fs_devices->opened) {
> seed_devices = fs_devices->seed;
> fs_devices->seed = NULL;
This still touches ->seed, and also reads ->opened, some locking is
required here or it has to be clearly explained why it's not.
> }
> - mutex_unlock(&uuid_mutex);
>
> while (seed_devices) {
> fs_devices = seed_devices;
> --
> 2.7.0
>
> --
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