linux-ext4 - Re: [PATCH 10/25] ext4: add EXT4_LBLK_TO_P and EXT4_P_TO

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Message-ID: <761b447d-6e34-4a6d-b1d8-9f744ab548db@huawei.com>
Date: Mon, 3 Nov 2025 22:45:45 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Jan Kara <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>,
	<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>, Baokun Li <libaokun@...weicloud.com>
Subject: Re: [PATCH 10/25] ext4: add EXT4_LBLK_TO_P and EXT4_P_TO_LBLK for
 block/page conversion

On 2025-11-03 16:26, Jan Kara wrote:
> On Sat 25-10-25 11:22:06, libaokun@...weicloud.com wrote:
>> From: Baokun Li <libaokun1@...wei.com>
>>
>> As BS > PS support is coming, all block number to page index (and
>> vice-versa) conversions must now go via bytes. Added EXT4_LBLK_TO_P()
>> and EXT4_P_TO_LBLK() macros to simplify these conversions and handle
>> both BS <= PS and BS > PS scenarios cleanly.
>>
>> Signed-off-by: Baokun Li <libaokun1@...wei.com>
>> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
> 'P' in the macro names seems too terse :). I'd probably use PG to give a
> better hint this is about pages? So EXT4_LBLK_TO_PG() and
> EXT4_PG_TO_LBLK(). 

Indeed, EXT4_LBLK_TO_PG reads much clearer. I will use it in v2.

> BTW, patch 8 could already use these macros...
>
> 								Honza

In Patch 8, the conversion is for a physical block number, which has a
different variable type than lblk. Since this is the only location where
this conversion is used in the code, I made a dedicated modification there.

Thank you for your review!


Cheers,
Baokun

>> ---
>>  fs/ext4/ext4.h | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index 9b236f620b3a..8223ed29b343 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -369,6 +369,12 @@ struct ext4_io_submit {
>>  	(round_up((offset), i_blocksize(inode)) >> (inode)->i_blkbits)
>>  #define EXT4_LBLK_TO_B(inode, lblk) ((loff_t)(lblk) << (inode)->i_blkbits)
>>  
>> +/* Translate a block number to a page index */
>> +#define EXT4_LBLK_TO_P(inode, lblk)	(EXT4_LBLK_TO_B((inode), (lblk)) >> \
>> +					 PAGE_SHIFT)
>> +/* Translate a page index to a block number */
>> +#define EXT4_P_TO_LBLK(inode, pnum)	(((loff_t)(pnum) << PAGE_SHIFT) >> \
>> +					 (inode)->i_blkbits)
>>  /* Translate a block number to a cluster number */
>>  #define EXT4_B2C(sbi, blk)	((blk) >> (sbi)->s_cluster_bits)
>>  /* Translate a cluster number to a block number */
>> -- 
>> 2.46.1
>>