On Mon, Nov 6, 2017 at 6:24 PM, David Sterba <dsterba@xxxxxxxx> wrote:
> The uuid_tree_rescan_sem is used as a mutex (initialized with value 1
> and with at most one active user), no reason to obscure that as a
> semaphore.
>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> ---
> fs/btrfs/ctree.h | 6 +++++-
> fs/btrfs/disk-io.c | 6 +++---
> fs/btrfs/super.c | 4 ++--
> fs/btrfs/volumes.c | 12 ++++++------
> 4 files changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index cab2f3607040..a643ff0fa0f0 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1073,7 +1073,11 @@ struct btrfs_fs_info {
> struct percpu_counter bio_counter;
> wait_queue_head_t replace_wait;
>
> - struct semaphore uuid_tree_rescan_sem;
> + /*
> + * Protect updating of uuid_tree, can be used to wait for the task
> + * completion
> + */
> + struct mutex uuid_tree_mutex;
>
> /* Used to reclaim the metadata space in the background. */
> struct work_struct async_reclaim_work;
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 53c9145a56e9..8330226234f2 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -2542,10 +2542,10 @@ int open_ctree(struct super_block *sb,
> mutex_init(&fs_info->cleaner_mutex);
> mutex_init(&fs_info->volume_mutex);
> mutex_init(&fs_info->ro_block_group_mutex);
> + mutex_init(&fs_info->uuid_tree_mutex);
> init_rwsem(&fs_info->commit_root_sem);
> init_rwsem(&fs_info->cleanup_work_sem);
> init_rwsem(&fs_info->subvol_sem);
> - sema_init(&fs_info->uuid_tree_rescan_sem, 1);
>
> btrfs_init_dev_replace_locks(fs_info);
> btrfs_init_qgroup(fs_info);
> @@ -3696,9 +3696,9 @@ void close_ctree(struct btrfs_fs_info *fs_info)
> btrfs_qgroup_wait_for_completion(fs_info, false);
>
> /* wait for the uuid_scan task to finish */
> - down(&fs_info->uuid_tree_rescan_sem);
> + mutex_lock(&fs_info->uuid_tree_mutex);
> /* avoid complains from lockdep et al., set sem back to initial state */
This comment should go away too.
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
>
> /* pause restriper - we want to resume on mount */
> btrfs_pause_balance(fs_info);
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 713f899bae81..5d0686c18bad 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -1777,9 +1777,9 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
> cancel_work_sync(&fs_info->async_reclaim_work);
>
> /* wait for the uuid_scan task to finish */
> - down(&fs_info->uuid_tree_rescan_sem);
> + mutex_lock(&fs_info->uuid_tree_mutex);
> /* avoid complains from lockdep et al. */
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
>
> sb->s_flags |= MS_RDONLY;
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 1b43f762906f..b2949232ba52 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4202,7 +4202,7 @@ static int btrfs_uuid_scan_kthread(void *data)
> btrfs_warn(fs_info, "btrfs_uuid_scan_kthread failed %d", ret);
> else
> set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
> return 0;
> }
>
> @@ -4264,7 +4264,7 @@ static int btrfs_uuid_rescan_kthread(void *data)
> ret = btrfs_uuid_tree_iterate(fs_info, btrfs_check_uuid_tree_entry);
> if (ret < 0) {
> btrfs_warn(fs_info, "iterating uuid_tree failed %d", ret);
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
> return ret;
> }
> return btrfs_uuid_scan_kthread(data);
> @@ -4301,12 +4301,12 @@ int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
> if (ret)
> return ret;
>
> - down(&fs_info->uuid_tree_rescan_sem);
> + mutex_lock(&fs_info->uuid_tree_mutex);
> task = kthread_run(btrfs_uuid_scan_kthread, fs_info, "btrfs-uuid");
> if (IS_ERR(task)) {
> /* fs_info->update_uuid_tree_gen remains 0 in all error case */
> btrfs_warn(fs_info, "failed to start uuid_scan task");
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
> return PTR_ERR(task);
> }
>
> @@ -4317,12 +4317,12 @@ int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info)
> {
> struct task_struct *task;
>
> - down(&fs_info->uuid_tree_rescan_sem);
> + mutex_lock(&fs_info->uuid_tree_mutex);
> task = kthread_run(btrfs_uuid_rescan_kthread, fs_info, "btrfs-uuid");
> if (IS_ERR(task)) {
> /* fs_info->update_uuid_tree_gen remains 0 in all error case */
> btrfs_warn(fs_info, "failed to start uuid_rescan task");
> - up(&fs_info->uuid_tree_rescan_sem);
> + mutex_unlock(&fs_info->uuid_tree_mutex);
> return PTR_ERR(task);
> }
>
> --
> 2.14.3
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
