linux-ext4 - Re: [PATCH 3/5] ext4: optimize to reduce redundant ext4

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Message-Id: <45DACE18-A3AD-41B0-B01A-F3B1135A2C0D@dilger.ca>
Date:   Mon, 4 Jun 2018 12:09:36 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Wang Shilong <wangshilong1991@...il.com>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Shuichi Ihara <sihara@....com>, Wang Shilong <wshilong@....com>
Subject: Re: [PATCH 3/5] ext4: optimize to reduce redundant ext4_error()

On May 29, 2018, at 5:45 AM, Wang Shilong <wangshilong1991@...il.com> wrote:
> 
> From: Wang Shilong <wshilong@....com>
> 
> only call ext4_error() if new corrupted bit set,
> this could save us repeated error messages and
> unecessary super block write.
> 
> Suggested-by: Andreas Dilger <adilger@...ger.ca>
> Signed-off-by: Wang Shilong <wshilong@....com>
> ---
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 554bceb..9f88991 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -766,21 +766,24 @@ void __ext4_grp_locked_error(const char *function,
> 
> -void __ext4_mark_group_bitmap_corrupted(struct super_block *sb,
> -					ext4_group_t group,
> -					unsigned int flags)
> +int __ext4_mark_group_bitmap_corrupted(struct super_block *sb,
> +				       ext4_group_t group,
> +				       unsigned int flags)
> {
> 	struct ext4_sb_info *sbi = EXT4_SB(sb);
> 	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
> 	struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL);
> 	int ret;
> +	int set = 0;
> 
> 	if (flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) {
> 		ret = ext4_test_and_set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
> 					    &grp->bb_state);
> -		if (!ret)
> +		if (!ret) {
> 			percpu_counter_sub(&sbi->s_freeclusters_counter,
> 					   grp->bb_free);
> +			set = 1;
> +		}
> 	}
> 
> 	if (flags & EXT4_GROUP_INFO_IBITMAP_CORRUPT) {
> @@ -792,8 +795,11 @@ void __ext4_mark_group_bitmap_corrupted(struct super_block *sb,
> 			count = ext4_free_inodes_count(sb, gdp);
> 			percpu_counter_sub(&sbi->s_freeinodes_counter,
> 					   count);
> +			set = 1;
> 		}
> 	}
> +
> +	return set;

Instead of adding a separate "set" variable, why not initialize "ret = 0"
and then return "!ret"?  It might be better to rename "ret" to something
more useful like "was_set" (which could be done in the original 1/5 patch).

Cheers, Andreas






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