linux-kernel - Re: [PATCH v2 2/2] ext4: Convert EXT4_B2C(sbi->s_stripe) users to EXT4_NUM

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Message-ID: <b28ae454-4907-a1ab-e0a3-1c8e85a32498@huaweicloud.com>
Date: Tue, 20 Aug 2024 20:48:48 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>, linux-ext4@...r.kernel.org,
 Theodore Ts'o <tytso@....edu>
Cc: Ritesh Harjani <ritesh.list@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ext4: Convert EXT4_B2C(sbi->s_stripe) users to
 EXT4_NUM_B2C



on 8/20/2024 5:27 PM, Ojaswin Mujoo wrote:
> Although we have checks to make sure s_stripe is a multiple of cluster
> size, in case we accidentally end up with a scenario where this is not
> the case, use EXT4_NUM_B2C() so that we don't end up with unexpected
> cases where EXT4_B2C(stripe) becomes 0.
> 
> Also make the is_stripe_aligned check in regular_allocator a bit more
> robust while we are at it. This should ideally have no functional change
> unless we have a bug somewhere causing (stripe % cluster_size != 0)
> 
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>Looks good to me. Feel free to add:

Reviewed-by: Kemeng Shi <shikemeng@...weicloud.com>
> ---
>  fs/ext4/mballoc.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 9dda9cd68ab2..99d1a8c730e0 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2553,7 +2553,7 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
>  	do_div(a, sbi->s_stripe);
>  	i = (a * sbi->s_stripe) - first_group_block;
>  
> -	stripe = EXT4_B2C(sbi, sbi->s_stripe);
> +	stripe = EXT4_NUM_B2C(sbi, sbi->s_stripe);
>  	i = EXT4_B2C(sbi, i);
>  	while (i < EXT4_CLUSTERS_PER_GROUP(sb)) {
>  		if (!mb_test_bit(i, bitmap)) {
> @@ -2928,9 +2928,11 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>  			if (cr == CR_POWER2_ALIGNED)
>  				ext4_mb_simple_scan_group(ac, &e4b);
>  			else {
> -				bool is_stripe_aligned = sbi->s_stripe &&
> +				bool is_stripe_aligned =
> +					(sbi->s_stripe >=
> +					 sbi->s_cluster_ratio) &&
>  					!(ac->ac_g_ex.fe_len %
> -					  EXT4_B2C(sbi, sbi->s_stripe));
> +					  EXT4_NUM_B2C(sbi, sbi->s_stripe));
>  
>  				if ((cr == CR_GOAL_LEN_FAST ||
>  				     cr == CR_BEST_AVAIL_LEN) &&
> @@ -3707,7 +3709,7 @@ int ext4_mb_init(struct super_block *sb)
>  	 */
>  	if (sbi->s_stripe > 1) {
>  		sbi->s_mb_group_prealloc = roundup(
> -			sbi->s_mb_group_prealloc, EXT4_B2C(sbi, sbi->s_stripe));
> +			sbi->s_mb_group_prealloc, EXT4_NUM_B2C(sbi, sbi->s_stripe));
>  	}
>  
>  	sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
>