Date:   Mon, 13 Mar 2023 07:37:21 +0530
Message-Id: <87wn3lflpi.fsf@doe.com>
From:   Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To:     Kemeng Shi <shikemeng@huaweicloud.com>, tytso@mit.edu,
        adilger.kernel@dilger.ca, ojaswin@linux.ibm.com
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        shikemeng@huaweicloud.com
Subject: Re: [PATCH v3 01/20] ext4: set goal start correctly in ext4_mb_normalize_request
In-Reply-To: <20230303172120.3800725-2-shikemeng@huaweicloud.com>
Precedence: bulk

Kemeng Shi <shikemeng@huaweicloud.com> writes:

> We need to set ac_g_ex to notify the goal start used in
> ext4_mb_find_by_goal. Set ac_g_ex instead of ac_f_ex in
> ext4_mb_normalize_request.
> Besides we should assure goal start is in range [first_data_block,
> blocks_count) as ext4_mb_initialize_context does.

Thanks for looking into the failed test case.
Patch looks good to me. After going through the change, I also feel we
should be updating ac_g_ex instead of ac_f_ex.

Good spotting! Please feel free to add -

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

>
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
> ---
>  fs/ext4/mballoc.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 5b2ae37a8b80..36cd545f5ab4 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -3993,6 +3993,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
>  				struct ext4_allocation_request *ar)
>  {
>  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
> +	struct ext4_super_block *es = sbi->s_es;
>  	int bsbits, max;
>  	ext4_lblk_t end;
>  	loff_t size, start_off;
> @@ -4188,18 +4189,20 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
>  	ac->ac_g_ex.fe_len = EXT4_NUM_B2C(sbi, size);
>
>  	/* define goal start in order to merge */
> -	if (ar->pright && (ar->lright == (start + size))) {
> +	if (ar->pright && (ar->lright == (start + size)) &&
> +	    ar->pright - size >= le32_to_cpu(es->s_first_data_block)) {
>  		/* merge to the right */
>  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pright - size,
> -						&ac->ac_f_ex.fe_group,
> -						&ac->ac_f_ex.fe_start);
> +						&ac->ac_g_ex.fe_group,
> +						&ac->ac_g_ex.fe_start);
>  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
>  	}
> -	if (ar->pleft && (ar->lleft + 1 == start)) {
> +	if (ar->pleft && (ar->lleft + 1 == start) &&
> +	    ar->pleft + 1 < ext4_blocks_count(es)) {
>  		/* merge to the left */
>  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pleft + 1,
> -						&ac->ac_f_ex.fe_group,
> -						&ac->ac_f_ex.fe_start);
> +						&ac->ac_g_ex.fe_group,
> +						&ac->ac_g_ex.fe_start);
>  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
>  	}
>
> --
> 2.30.0