Date:   Thu, 9 Mar 2023 15:25:04 +0100
From:   Jan Kara <jack@suse.cz>
To:     Ojaswin Mujoo <ojaswin@linux.ibm.com>
Cc:     linux-ext4@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
        Ritesh Harjani <riteshh@linux.ibm.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jan Kara <jack@suse.cz>, Ritesh Harjani <ritesh.list@gmail.com>
Subject: Re: [RFC 10/11] ext4: Abstract out logic to search average fragment
 list
Message-ID: <20230309142504.5lodm4inrn7bnfmk@quack3>
References: <cover.1674822311.git.ojaswin@linux.ibm.com>
 <3f0afae57eeaf47aa4b980eddc5e54efc78efa66.1674822311.git.ojaswin@linux.ibm.com>
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On Fri 27-01-23 18:07:37, Ojaswin Mujoo wrote:
> Make the logic of searching average fragment list of a given order reusable
> by abstracting it out to a differnet function. This will also avoid
> code duplication in upcoming patches.
> 
> No functional changes.
> 
> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/mballoc.c | 51 ++++++++++++++++++++++++++++++-----------------
>  1 file changed, 33 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 410c9636907b..1ce1174aea52 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -902,6 +902,37 @@ static void ext4_mb_choose_next_group_cr0(struct ext4_allocation_context *ac,
>  	}
>  }
>  
> +/*
> + * Find a suitable group of given order from the average fragments list.
> + */
> +static struct ext4_group_info *
> +ext4_mb_find_good_group_avg_frag_lists(struct ext4_allocation_context *ac, int order)
> +{
> +	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
> +	struct list_head *frag_list = &sbi->s_mb_avg_fragment_size[order];
> +	rwlock_t *frag_list_lock = &sbi->s_mb_avg_fragment_size_locks[order];
> +	struct ext4_group_info *grp = NULL, *iter;
> +	enum criteria cr = ac->ac_criteria;
> +
> +	if (list_empty(frag_list))
> +		return NULL;
> +	read_lock(frag_list_lock);
> +	if (list_empty(frag_list)) {
> +		read_unlock(frag_list_lock);
> +		return NULL;
> +	}
> +	list_for_each_entry(iter, frag_list, bb_avg_fragment_size_node) {
> +		if (sbi->s_mb_stats)
> +			atomic64_inc(&sbi->s_bal_cX_groups_considered[cr]);
> +		if (likely(ext4_mb_good_group(ac, iter->bb_group, cr))) {
> +			grp = iter;
> +			break;
> +		}
> +	}
> +	read_unlock(frag_list_lock);
> +	return grp;
> +}
> +
>  /*
>   * Choose next group by traversing average fragment size list of suitable
>   * order. Updates *new_cr if cr level needs an update.
> @@ -910,7 +941,7 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac,
>  		enum criteria *new_cr, ext4_group_t *group, ext4_group_t ngroups)
>  {
>  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
> -	struct ext4_group_info *grp = NULL, *iter;
> +	struct ext4_group_info *grp = NULL;
>  	int i;
>  
>  	if (unlikely(ac->ac_flags & EXT4_MB_CR1_OPTIMIZED)) {
> @@ -920,23 +951,7 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac,
>  
>  	for (i = mb_avg_fragment_size_order(ac->ac_sb, ac->ac_g_ex.fe_len);
>  	     i < MB_NUM_ORDERS(ac->ac_sb); i++) {
> -		if (list_empty(&sbi->s_mb_avg_fragment_size[i]))
> -			continue;
> -		read_lock(&sbi->s_mb_avg_fragment_size_locks[i]);
> -		if (list_empty(&sbi->s_mb_avg_fragment_size[i])) {
> -			read_unlock(&sbi->s_mb_avg_fragment_size_locks[i]);
> -			continue;
> -		}
> -		list_for_each_entry(iter, &sbi->s_mb_avg_fragment_size[i],
> -				    bb_avg_fragment_size_node) {
> -			if (sbi->s_mb_stats)
> -				atomic64_inc(&sbi->s_bal_cX_groups_considered[CR1]);
> -			if (likely(ext4_mb_good_group(ac, iter->bb_group, CR1))) {
> -				grp = iter;
> -				break;
> -			}
> -		}
> -		read_unlock(&sbi->s_mb_avg_fragment_size_locks[i]);
> +		grp = ext4_mb_find_good_group_avg_frag_lists(ac, i);
>  		if (grp)
>  			break;
>  	}
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR