Re: [PATCH V2 2/7] ext4: add new helper interface ext4_try_to_trim_range()

[Andreas Dilger <adilger@dilger.ca>]

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On May 26, 2021, at 2:43 AM, Wang Jianchao <jianchao.wan9@gmail.com> wrote:
> 
> There is no functional change in this patch but just split the
> codes, which serachs free block and does trim, into a new function
> ext4_try_to_trim_range. This is preparing for the following async
> backgroup discard.
> 
> Signed-off-by: Wang Jianchao <wangjianchao@kuaishou.com>

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

> ---
> fs/ext4/mballoc.c | 102 ++++++++++++++++++++++++++++++------------------------
> 1 file changed, 57 insertions(+), 45 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index d81f1fd22..f984f15 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -5685,6 +5685,54 @@ static int ext4_trim_extent(struct super_block *sb,
> 	return ret;
> }
> 
> +static int ext4_try_to_trim_range(struct super_block *sb,
> +		struct ext4_buddy *e4b, ext4_grpblk_t start,
> +		ext4_grpblk_t max, ext4_grpblk_t minblocks)
> +{
> +	ext4_grpblk_t next, count, free_count;
> +	void *bitmap;
> +	int ret = 0;
> +
> +	bitmap = e4b->bd_bitmap;
> +	start = (e4b->bd_info->bb_first_free > start) ?
> +		e4b->bd_info->bb_first_free : start;
> +	count = 0;
> +	free_count = 0;
> +
> +	while (start <= max) {
> +		start = mb_find_next_zero_bit(bitmap, max + 1, start);
> +		if (start > max)
> +			break;
> +		next = mb_find_next_bit(bitmap, max + 1, start);
> +
> +		if ((next - start) >= minblocks) {
> +			ret = ext4_trim_extent(sb, start, next - start, e4b);
> +			if (ret && ret != -EOPNOTSUPP)
> +				break;
> +			ret = 0;
> +			count += next - start;
> +		}
> +		free_count += next - start;
> +		start = next + 1;
> +
> +		if (fatal_signal_pending(current)) {
> +			count = -ERESTARTSYS;
> +			break;
> +		}
> +
> +		if (need_resched()) {
> +			ext4_unlock_group(sb, e4b->bd_group);
> +			cond_resched();
> +			ext4_lock_group(sb, e4b->bd_group);
> +		}
> +
> +		if ((e4b->bd_info->bb_free - free_count) < minblocks)
> +			break;
> +	}
> +
> +	return count;
> +}
> +
> /**
>  * ext4_trim_all_free -- function to trim all free space in alloc. group
>  * @sb:			super block for file system
> @@ -5708,10 +5756,8 @@ static int ext4_trim_extent(struct super_block *sb,
> 		   ext4_grpblk_t start, ext4_grpblk_t max,
> 		   ext4_grpblk_t minblocks)
> {
> -	void *bitmap;
> -	ext4_grpblk_t next, count = 0, free_count = 0;
> 	struct ext4_buddy e4b;
> -	int ret = 0;
> +	int ret;
> 
> 	trace_ext4_trim_all_free(sb, group, start, max);
> 
> @@ -5721,57 +5767,23 @@ static int ext4_trim_extent(struct super_block *sb,
> 			     ret, group);
> 		return ret;
> 	}
> -	bitmap = e4b.bd_bitmap;
> 
> 	ext4_lock_group(sb, group);
> -	if (EXT4_MB_GRP_WAS_TRIMMED(e4b.bd_info) &&
> -	    minblocks >= atomic_read(&EXT4_SB(sb)->s_last_trim_minblks))
> -		goto out;
> -
> -	start = (e4b.bd_info->bb_first_free > start) ?
> -		e4b.bd_info->bb_first_free : start;
> 
> -	while (start <= max) {
> -		start = mb_find_next_zero_bit(bitmap, max + 1, start);
> -		if (start > max)
> -			break;
> -		next = mb_find_next_bit(bitmap, max + 1, start);
> -
> -		if ((next - start) >= minblocks) {
> -			ret = ext4_trim_extent(sb, start, next - start, &e4b);
> -			if (ret && ret != -EOPNOTSUPP)
> -				break;
> -			ret = 0;
> -			count += next - start;
> -		}
> -		free_count += next - start;
> -		start = next + 1;
> -
> -		if (fatal_signal_pending(current)) {
> -			count = -ERESTARTSYS;
> -			break;
> -		}
> -
> -		if (need_resched()) {
> -			ext4_unlock_group(sb, group);
> -			cond_resched();
> -			ext4_lock_group(sb, group);
> -		}
> -
> -		if ((e4b.bd_info->bb_free - free_count) < minblocks)
> -			break;
> +	if (!EXT4_MB_GRP_WAS_TRIMMED(e4b.bd_info) ||
> +	    minblocks < atomic_read(&EXT4_SB(sb)->s_last_trim_minblks)) {
> +		ret = ext4_try_to_trim_range(sb, &e4b, start, max, minblocks);
> +		if (ret >= 0)
> +			EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
> +	} else {
> +		ret = 0;
> 	}
> 
> -	if (!ret) {
> -		ret = count;
> -		EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
> -	}
> -out:
> 	ext4_unlock_group(sb, group);
> 	ext4_mb_unload_buddy(&e4b);
> 
> 	ext4_debug("trimmed %d blocks in the group %d\n",
> -		count, group);
> +		ret, group);
> 
> 	return ret;
> }
> --
> 1.8.3.1


Cheers, Andreas






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