Re: [PATCH v2] f2fs: Don't create discard thread when device not support realtime discard

[Chao Yu]

On 2021/8/13 18:11, Yangtao Li wrote:
> From: Fengnan Chang <changfengnan@xxxxxxxx>
>
> Don't create discard thread when device not support realtime discard.
>
> Signed-off-by: Fengnan Chang <changfengnan@xxxxxxxx>
> Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
> ---
>   fs/f2fs/f2fs.h    |  1 +
>   fs/f2fs/segment.c | 29 +++++++++++++++++++++--------
>   fs/f2fs/super.c   | 34 ++++++++++++++++++++++++++++++++--
>   3 files changed, 54 insertions(+), 10 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index d24fd5045712..60a408af53a3 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3483,6 +3483,7 @@ int f2fs_flush_device_cache(struct f2fs_sb_info *sbi);
>   void f2fs_destroy_flush_cmd_control(struct f2fs_sb_info *sbi, bool free);
>   void f2fs_invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr);
>   bool f2fs_is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
> +int f2fs_start_discard_thread(struct f2fs_sb_info *sbi);
>   void f2fs_drop_discard_cmd(struct f2fs_sb_info *sbi);
>   void f2fs_stop_discard_thread(struct f2fs_sb_info *sbi);
>   bool f2fs_issue_discard_timeout(struct f2fs_sb_info *sbi);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index ca9876a6d396..b83a4a1e5023 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2112,7 +2112,27 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>   wakeup:
>   	wake_up_discard_thread(sbi, false);
>   }

Need a blank line here.

> +int f2fs_start_discard_thread(struct f2fs_sb_info *sbi)
> +{
> +	dev_t dev = sbi->sb->s_bdev->bd_dev;
> +	struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> +	int err = 0;
>   
> +	if (!dcc)
> +		return -EINVAL;
> +	if (!f2fs_realtime_discard_enable(sbi))
> +		return 0;
> +
> +	dcc->f2fs_issue_discard = kthread_run(issue_discard_thread, sbi,
> +				"f2fs_discard-%u:%u", MAJOR(dev), MINOR(dev));
> +	if (IS_ERR(dcc->f2fs_issue_discard)) {
> +		err = PTR_ERR(dcc->f2fs_issue_discard);
> +		kfree(dcc);
> +		SM_I(sbi)->dcc_info = NULL;
> +		return err;
> +	}
> +	return err;
> +}

Ditto,

>   static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>   {
>   	dev_t dev = sbi->sb->s_bdev->bd_dev;

Need to remove unused dev.

> @@ -2153,14 +2173,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
>   	init_waitqueue_head(&dcc->discard_wait_queue);
>   	SM_I(sbi)->dcc_info = dcc;
>   init_thread:
> -	dcc->f2fs_issue_discard = kthread_run(issue_discard_thread, sbi,
> -				"f2fs_discard-%u:%u", MAJOR(dev), MINOR(dev));
> -	if (IS_ERR(dcc->f2fs_issue_discard)) {
> -		err = PTR_ERR(dcc->f2fs_issue_discard);
> -		kfree(dcc);
> -		SM_I(sbi)->dcc_info = NULL;
> -		return err;
> -	}
> +	err = f2fs_start_discard_thread(sbi);
>   
>   	return err;

return f2fs_start_discard_thread(sbi);

err becomes unused.

>   }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 84cd085020cd..ff19c30cd6a1 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2101,12 +2101,15 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   	bool need_restart_gc = false, need_stop_gc = false;
>   	bool need_restart_ckpt = false, need_stop_ckpt = false;
>   	bool need_restart_flush = false, need_stop_flush = false;
> +	bool need_enable_ckpt = false, need_disable_ckpt = false;
>   	bool no_extent_cache = !test_opt(sbi, EXTENT_CACHE);
>   	bool enable_checkpoint = !test_opt(sbi, DISABLE_CHECKPOINT);
>   	bool no_io_align = !F2FS_IO_ALIGNED(sbi);
>   	bool no_atgc = !test_opt(sbi, ATGC);
> +	bool no_discard = !test_opt(sbi, DISCARD);
>   	bool no_compress_cache = !test_opt(sbi, COMPRESS_CACHE);
>   	bool block_unit_discard = f2fs_block_unit_discard(sbi);
> +	struct discard_cmd_control *dcc;
>   #ifdef CONFIG_QUOTA
>   	int i, j;
>   #endif
> @@ -2274,7 +2277,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   	} else {
>   		err = f2fs_create_flush_cmd_control(sbi);
>   		if (err)
> -			goto restore_ckpt;
> +			goto restore_ckpt_thread;
>   		need_stop_flush = true;
>   	}
>   
> @@ -2283,8 +2286,28 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   			err = f2fs_disable_checkpoint(sbi);
>   			if (err)
>   				goto restore_flush;
> +			need_enable_ckpt = true;
>   		} else {
>   			f2fs_enable_checkpoint(sbi);
> +			need_disable_ckpt = true;
> +		}
> +	}
> +
> +	if (no_discard == !!test_opt(sbi, DISCARD)) {
> +		if (test_opt(sbi, DISCARD)) {
> +			err = f2fs_start_discard_thread(sbi);
> +			if (err)
> +				goto restore_ckpt;
> +

Unneeded blank line.

> +		} else {
> +			dcc = SM_I(sbi)->dcc_info;
> +			if (!dcc) {
> +				err = -EINVAL;
> +				goto restore_ckpt;
> +			}
> +			f2fs_stop_discard_thread(sbi);
> +			if (unlikely(atomic_read(&dcc->discard_cmd_cnt)))

I don't think this is an unlikely case.

> +				f2fs_issue_discard_timeout(sbi);

How about starting/stopping discard thread after flush thread status update,
leaving complicated checkpoint disabling status change in the last stage of
remount().

Thanks,

>   		}
>   	}
>   
> @@ -2302,6 +2325,13 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   	adjust_unusable_cap_perc(sbi);
>   	*flags = (*flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME);
>   	return 0;
> +restore_ckpt:
> +	if (need_enable_ckpt) {
> +		f2fs_enable_checkpoint(sbi);
> +	} else if (need_disable_ckpt) {
> +		if (f2fs_disable_checkpoint(sbi))
> +			f2fs_warn(sbi, "checkpoint has been enable");
> +	}
>   restore_flush:
>   	if (need_restart_flush) {
>   		if (f2fs_create_flush_cmd_control(sbi))
> @@ -2310,7 +2340,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>   		clear_opt(sbi, FLUSH_MERGE);
>   		f2fs_destroy_flush_cmd_control(sbi, false);
>   	}
> -restore_ckpt:
> +restore_ckpt_thread:
>   	if (need_restart_ckpt) {
>   		if (f2fs_start_ckpt_thread(sbi))
>   			f2fs_warn(sbi, "background ckpt thread has stopped");