Re: [PATCH V7 07/17] xfs: Introduce XFS_SB_FEAT_INCOMPAT_NREXT64 and associated per-fs feature bit

Chandan Babu R
2022-03-05T12:44:04Z

On 04 Mar 2022 at 07:27, Dave Chinner wrote:
> On Tue, Mar 01, 2022 at 04:09:28PM +0530, Chandan Babu R wrote:
>> XFS_SB_FEAT_INCOMPAT_NREXT64 incompat feature bit will be set on filesystems
>> which support large per-inode extent counters. This commit defines the new
>> incompat feature bit and the corresponding per-fs feature bit (along with
>> inline functions to work on it).
>>
>> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
>> ---
>> fs/xfs/libxfs/xfs_format.h | 1 +
>> fs/xfs/libxfs/xfs_sb.c | 3 +++
>> fs/xfs/xfs_mount.h | 2 ++
>> 3 files changed, 6 insertions(+)
>>
>> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
>> index e5654b578ec0..7972cbc22608 100644
>> --- a/fs/xfs/libxfs/xfs_format.h
>> +++ b/fs/xfs/libxfs/xfs_format.h
>> @@ -372,6 +372,7 @@ xfs_sb_has_ro_compat_feature(
>> #define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 2) /* metadata UUID */
>> #define XFS_SB_FEAT_INCOMPAT_BIGTIME (1 << 3) /* large timestamps */
>> #define XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR (1 << 4) /* needs xfs_repair */
>> +#define XFS_SB_FEAT_INCOMPAT_NREXT64 (1 << 5) /* 64-bit data fork extent counter */
>> #define XFS_SB_FEAT_INCOMPAT_ALL \
>> (XFS_SB_FEAT_INCOMPAT_FTYPE| \
>> XFS_SB_FEAT_INCOMPAT_SPINODES| \
>> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
>> index f4e84aa1d50a..bd632389ae92 100644
>> --- a/fs/xfs/libxfs/xfs_sb.c
>> +++ b/fs/xfs/libxfs/xfs_sb.c
>> @@ -124,6 +124,9 @@ xfs_sb_version_to_features(
>> features |= XFS_FEAT_BIGTIME;
>> if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR)
>> features |= XFS_FEAT_NEEDSREPAIR;
>> + if (sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_NREXT64)
>> + features |= XFS_FEAT_NREXT64;
>> +
>> return features;
>> }
>>
>> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
>> index 00720a02e761..10941481f7e6 100644
>> --- a/fs/xfs/xfs_mount.h
>> +++ b/fs/xfs/xfs_mount.h
>> @@ -276,6 +276,7 @@ typedef struct xfs_mount {
>> #define XFS_FEAT_INOBTCNT (1ULL << 23) /* inobt block counts */
>> #define XFS_FEAT_BIGTIME (1ULL << 24) /* large timestamps */
>> #define XFS_FEAT_NEEDSREPAIR (1ULL << 25) /* needs xfs_repair */
>> +#define XFS_FEAT_NREXT64 (1ULL << 26) /* 64-bit inode extent counters */
>>
>> /* Mount features */
>> #define XFS_FEAT_NOATTR2 (1ULL << 48) /* disable attr2 creation */
>> @@ -338,6 +339,7 @@ __XFS_HAS_FEAT(realtime, REALTIME)
>> __XFS_HAS_FEAT(inobtcounts, INOBTCNT)
>> __XFS_HAS_FEAT(bigtime, BIGTIME)
>> __XFS_HAS_FEAT(needsrepair, NEEDSREPAIR)
>> +__XFS_HAS_FEAT(nrext64, NREXT64)
>
> Not a big fan of "nrext64" naming.
>
> I'd really like the feature macro to be human readable such as:
>
> __XFS_HAS_FEAT(large_extent_counts, NREXT64)
>
> So that it reads like this:
>
> if (xfs_has_large_extent_counts(mp)) {
> .....
> }
>
> because then the code is much easier to read and is largely self
> documenting. In this case, I don't really care about the flag names
> (they can remain NREXT64) because they are only seen deep down in
> the code. But for (potentially complex) conditional logic, the
> clarity of human readable names makes a big difference.
>

Ok. I will rename the feature.

--
chandan