On Sat, Jul 24, 2021 at 03:41:23PM +0800, Wang Jianchao wrote:
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 34be2f07449d..a496509e61b7 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -3474,6 +3530,14 @@ int ext4_mb_release(struct super_block *sb)
> struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits);
> int count;
>
> + if (test_opt(sb, DISCARD)) {
> + /*
> + * wait the discard work to drain all of ext4_free_data
> + */
> + queue_work(ext4_discard_wq, &sbi->s_discard_work);
> + flush_work(&sbi->s_discard_work);
I agree with Jan --- it's not clear to me why the call to queue_work()
is needed. After the flush_work() call returns, if s_discard_work is
still non-empty, there must be something terribly wrong --- are we
missing something?
> @@ -3672,8 +3724,14 @@ int __init ext4_init_mballoc(void)
> if (ext4_free_data_cachep == NULL)
> goto out_ac_free;
>
> + ext4_discard_wq = alloc_workqueue("ext4discard", WQ_UNBOUND, 0);
> + if (!ext4_discard_wq)
> + goto out_free_data;
> +
Perhaps we should only allocate the workqueue when it's needed ---
e.g., when a file system is mounted or remounted with "-o discard"?
Then in ext4_exit_malloc(), we only free it if ext4_discard_wq is
non-NULL.
This would save a bit of memory on systems that wouldn't need the ext4
discard work queue.
- Ted
