linux-ext4 - Re: [PATCH 11/25] ext4: support large block size in ext4_mb_load_buddy

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Message-ID: <sesj43tzk243dgm7vmk2cvqy66gh57dd65yhebxf6pkmliblfr@6adx5sry5eog>
Date: Wed, 5 Nov 2025 09:46:58 +0100
From: Jan Kara <jack@...e.cz>
To: libaokun@...weicloud.com
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, 
	jack@...e.cz, linux-kernel@...r.kernel.org, kernel@...kajraghav.com, 
	mcgrof@...nel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
	yi.zhang@...wei.com, yangerkun@...wei.com, chengzhihao1@...wei.com, 
	libaokun1@...wei.com
Subject: Re: [PATCH 11/25] ext4: support large block size in
 ext4_mb_load_buddy_gfp()

On Sat 25-10-25 11:22:07, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> Currently, ext4_mb_load_buddy_gfp() uses blocks_per_page to calculate the
> folio index and offset. However, when blocksize is larger than PAGE_SIZE,
> blocks_per_page becomes zero, leading to a potential division-by-zero bug.
> 
> To support BS > PS, use bytes to compute folio index and offset within
> folio to get rid of blocks_per_page.
> 
> Also, if buddy and bitmap land in the same folio, we get that folio’s ref
> instead of looking it up again before updating the buddy.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

Looks good! Feel free to add:

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

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR