Messages in this thread | | | Date | Thu, 12 Aug 2021 15:46:50 -0400 | From | "Theodore Ts'o" <> | Subject | Re: [PATCH V3 4/5] ext4: get discard out of jbd2 commit kthread contex |
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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
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