Re: [RFC 2/3] xfs: Refactoring the nagcount and delta calculation

["Nirjhar Roy (IBM)" <nirjhar.roy.lists@gmail.com>]

On 7/30/25 01:54, Darrick J. Wong wrote:
> On Thu, Jul 17, 2025 at 04:00:44PM +0530, Nirjhar Roy (IBM) wrote:
>> Introduce xfs_growfs_get_delta() to calculate the nagcount
>> and delta blocks and refactor the code from xfs_growfs_data_private().
>> No functional changes.
>>
>> Signed-off-by: Nirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
>> ---
>>   fs/xfs/libxfs/xfs_ag.c | 25 +++++++++++++++++++++++++
>>   fs/xfs/libxfs/xfs_ag.h |  3 +++
>>   fs/xfs/xfs_fsops.c     | 17 ++---------------
>>   3 files changed, 30 insertions(+), 15 deletions(-)
>>
>> diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
>> index e6ba914f6d06..dcaf5683028e 100644
>> --- a/fs/xfs/libxfs/xfs_ag.c
>> +++ b/fs/xfs/libxfs/xfs_ag.c
>> @@ -872,6 +872,31 @@ xfs_ag_shrink_space(
>>   	return err2;
>>   }
>>   
>> +void
>> +xfs_growfs_get_delta(struct xfs_mount *mp, xfs_rfsblock_t nb,
> /me suggests xfs_growfs_compute_deltas() but otherwise this hoist looks
> fine to me;
Okay. I will make the change in the next revision.
>
> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Thank you.
>
> --D
>
>> +	int64_t *deltap, xfs_agnumber_t *nagcountp)
>> +{
>> +	xfs_rfsblock_t nb_div, nb_mod;
>> +	int64_t delta;
>> +	xfs_agnumber_t nagcount;
>> +
>> +	nb_div = nb;
>> +	nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks);
>> +	if (nb_mod && nb_mod >= XFS_MIN_AG_BLOCKS)
>> +		nb_div++;
>> +	else if (nb_mod)
>> +		nb = nb_div * mp->m_sb.sb_agblocks;
>> +
>> +	if (nb_div > XFS_MAX_AGNUMBER + 1) {
>> +		nb_div = XFS_MAX_AGNUMBER + 1;
>> +		nb = nb_div * mp->m_sb.sb_agblocks;
>> +	}
>> +	nagcount = nb_div;
>> +	delta = nb - mp->m_sb.sb_dblocks;
>> +	*deltap = delta;
>> +	*nagcountp = nagcount;
>> +}
>> +
>>   /*
>>    * Extent the AG indicated by the @id by the length passed in
>>    */
>> diff --git a/fs/xfs/libxfs/xfs_ag.h b/fs/xfs/libxfs/xfs_ag.h
>> index 1f24cfa27321..190af11f6941 100644
>> --- a/fs/xfs/libxfs/xfs_ag.h
>> +++ b/fs/xfs/libxfs/xfs_ag.h
>> @@ -331,6 +331,9 @@ struct aghdr_init_data {
>>   int xfs_ag_init_headers(struct xfs_mount *mp, struct aghdr_init_data *id);
>>   int xfs_ag_shrink_space(struct xfs_perag *pag, struct xfs_trans **tpp,
>>   			xfs_extlen_t delta);
>> +void
>> +xfs_growfs_get_delta(struct xfs_mount *mp, xfs_rfsblock_t nb,
>> +	int64_t *deltap, xfs_agnumber_t *nagcountp);
>>   int xfs_ag_extend_space(struct xfs_perag *pag, struct xfs_trans *tp,
>>   			xfs_extlen_t len);
>>   int xfs_ag_get_geometry(struct xfs_perag *pag, struct xfs_ag_geometry *ageo);
>> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
>> index 0ada73569394..91da9f733659 100644
>> --- a/fs/xfs/xfs_fsops.c
>> +++ b/fs/xfs/xfs_fsops.c
>> @@ -92,18 +92,17 @@ xfs_growfs_data_private(
>>   	struct xfs_growfs_data	*in)		/* growfs data input struct */
>>   {
>>   	xfs_agnumber_t		oagcount = mp->m_sb.sb_agcount;
>> +	xfs_rfsblock_t nb = in->newblocks;
>>   	struct xfs_buf		*bp;
>>   	int			error;
>>   	xfs_agnumber_t		nagcount;
>>   	xfs_agnumber_t		nagimax = 0;
>> -	xfs_rfsblock_t		nb, nb_div, nb_mod;
>>   	int64_t			delta;
>>   	bool			lastag_extended = false;
>>   	struct xfs_trans	*tp;
>>   	struct aghdr_init_data	id = {};
>>   	struct xfs_perag	*last_pag;
>>   
>> -	nb = in->newblocks;
>>   	error = xfs_sb_validate_fsb_count(&mp->m_sb, nb);
>>   	if (error)
>>   		return error;
>> @@ -122,20 +121,8 @@ xfs_growfs_data_private(
>>   			mp->m_sb.sb_rextsize);
>>   	if (error)
>>   		return error;
>> +	xfs_growfs_get_delta(mp, nb, &delta, &nagcount);
>>   
>> -	nb_div = nb;
>> -	nb_mod = do_div(nb_div, mp->m_sb.sb_agblocks);
>> -	if (nb_mod && nb_mod >= XFS_MIN_AG_BLOCKS)
>> -		nb_div++;
>> -	else if (nb_mod)
>> -		nb = nb_div * mp->m_sb.sb_agblocks;
>> -
>> -	if (nb_div > XFS_MAX_AGNUMBER + 1) {
>> -		nb_div = XFS_MAX_AGNUMBER + 1;
>> -		nb = nb_div * mp->m_sb.sb_agblocks;
>> -	}
>> -	nagcount = nb_div;
>> -	delta = nb - mp->m_sb.sb_dblocks;
>>   	/*
>>   	 * Reject filesystems with a single AG because they are not
>>   	 * supported, and reject a shrink operation that would cause a
>> -- 
>> 2.43.5
>>
>>
-- 
Nirjhar Roy
Linux Kernel Developer
IBM, Bangalore