Re: [PATCH V2 02/12] xfs: Rename MAXEXTNUM, MAXAEXTNUM to XFS_IFORK_EXTCNT_MAXS32, XFS_IFORK_EXTCNT_MAXS16

From: Chandan Babu R <chandanrlinux@gmail.com>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH V2 02/12] xfs: Rename MAXEXTNUM, MAXAEXTNUM to XFS_IFORK_EXTCNT_MAXS32, XFS_IFORK_EXTCNT_MAXS16
Date: Mon, 23 Aug 2021 12:47:43 +0530	[thread overview]
Message-ID: <87v93wfx48.fsf@debian-BULLSEYE-live-builder-AMD64> (raw)
In-Reply-To: <87y28sg5e5.fsf@debian-BULLSEYE-live-builder-AMD64>

On 23 Aug 2021 at 09:48, Chandan Babu R wrote:
> On 28 Jul 2021 at 08:45, Chandan Babu R wrote:
>> On 28 Jul 2021 at 03:33, Darrick J. Wong wrote:
>>> On Tue, Jul 27, 2021 at 02:56:11PM -0700, Darrick J. Wong wrote:
>>>> On Mon, Jul 26, 2021 at 05:15:31PM +0530, Chandan Babu R wrote:
>>>> > In preparation for introducing larger extent count limits, this commit renames
>>>> > existing extent count limits based on their signedness and width.
>>>> > 
>>>> > Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
>>>> > ---
>>>> >  fs/xfs/libxfs/xfs_bmap.c       | 4 ++--
>>>> >  fs/xfs/libxfs/xfs_format.h     | 8 ++++----
>>>> >  fs/xfs/libxfs/xfs_inode_buf.c  | 4 ++--
>>>> >  fs/xfs/libxfs/xfs_inode_fork.c | 3 ++-
>>>> >  fs/xfs/scrub/inode_repair.c    | 2 +-
>>>> >  5 files changed, 11 insertions(+), 10 deletions(-)
>>>> > 
>>>> > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
>>>> > index f3c9a0ebb0a5..8f262405a5b5 100644
>>>> > --- a/fs/xfs/libxfs/xfs_bmap.c
>>>> > +++ b/fs/xfs/libxfs/xfs_bmap.c
>>>> > @@ -76,10 +76,10 @@ xfs_bmap_compute_maxlevels(
>>>> >  	 * available.
>>>> >  	 */
>>>> >  	if (whichfork == XFS_DATA_FORK) {
>>>> > -		maxleafents = MAXEXTNUM;
>>>> > +		maxleafents = XFS_IFORK_EXTCNT_MAXS32;
>>>> 
>>>> I'm not in love with these names, since they tell me roughly about the
>>>> size of the constant (which I could glean from the definition) but less
>>>> about when I would expect to find them.  How about:
>>>> 
>>>> #define XFS_MAX_DFORK_NEXTENTS    ((xfs_extnum_t) 0x7FFFFFFF)
>>>> #define XFS_MAX_AFORK_NEXTENTS    ((xfs_aextnum_t)0x00007FFF)
>>>
>>> Or, given that 'DFORK' already means 'ondisk fork', how about:
>>>
>>> XFS_MAX_DATA_NEXTENTS
>>> XFS_MAX_ATTR_NEXTENTS
>>
>> Yes, I agree. These names are better. I will incorporate your suggestions
>> before posting V3.
>>
>
> Using XFS_MAX_[ATTR|DATA]_NEXTENTS won't be feasible later in the patch series
> since the maximum extent count for the two inode forks depend on whether
> XFS_SB_FEAT_INCOMPAT_NREXT64 feature bit is set or not. With the incompat
> feature bit set, extent counts for attr and data forks can have maximum values
> of (2^32 - 1) and (2^48 - 1) respectively. With the incompat feature bit not
> set, extent counts for attr and data forks can have maximum values of (2^15 -
> 1) and (2^31 - 1) respectively.
>
> Also, xfs_iext_max_nextents() (an inline function introduced in the next patch
> in this series) abstracts away the logic of determining the maximum extent
> count for an inode fork.

I think introducing xfs_iext_max_nextents() before renaming the max extent
counter macros would reduce proliferation of XFS_IFORK_EXTCNT_MAX* macros
across the source code. If you are ok with it, I will reorder the current
patch and the next patch.

-- 
chandan