Re: [PATCH V3 09/12] xfs: Enable bulkstat ioctl to support 64-bit per-inode extent counters

From: Chandan Babu R <chandan.babu@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org, djwong@kernel.org
Subject: Re: [PATCH V3 09/12] xfs: Enable bulkstat ioctl to support 64-bit per-inode extent counters
Date: Tue, 28 Sep 2021 15:19:29 +0530	[thread overview]
Message-ID: <87zgrxyqqe.fsf@debian-BULLSEYE-live-builder-AMD64> (raw)
In-Reply-To: <20210927230637.GL1756565@dread.disaster.area>

On 28 Sep 2021 at 04:36, Dave Chinner wrote:
> On Thu, Sep 16, 2021 at 03:36:44PM +0530, Chandan Babu R wrote:
>> The following changes are made to enable userspace to obtain 64-bit extent
>> counters,
>> 1. To hold 64-bit extent counters, carve out the new 64-bit field
>>    xfs_bulkstat->bs_extents64 from xfs_bulkstat->bs_pad[].
>> 2. Carve out a new 64-bit field xfs_bulk_ireq->bulkstat_flags from
>>    xfs_bulk_ireq->reserved[] to hold bulkstat specific operational flags.  As of
>>    this commit, XFS_IBULK_NREXT64 is the only valid flag that this field can
>>    hold. It indicates that userspace has the necessary infrastructure to
>>    receive 64-bit extent counters.
>> 3. Define the new flag XFS_BULK_IREQ_BULKSTAT for userspace to indicate that
>>    xfs_bulk_ireq->bulkstat_flags has valid flags set.
>
> This seems unnecessarily complex. It adds a new flag to define a new
> flag field in the same structure and then define a new and a new
> flag in the new flag field to define a new behaviour.
>
> Why can't this be done with just a single new flag in the existing
> flags field?
>

Yes, This can be implemented with just one flag. I will make the relevant
changes before posting the next version.

>> Suggested-by: Darrick J. Wong <djwong@kernel.org>
>> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
>> ---
>>  fs/xfs/libxfs/xfs_fs.h | 19 ++++++++++++++-----
>>  fs/xfs/xfs_ioctl.c     |  7 +++++++
>>  fs/xfs/xfs_itable.c    | 25 +++++++++++++++++++++++--
>>  fs/xfs/xfs_itable.h    |  2 ++
>>  fs/xfs/xfs_iwalk.h     |  7 +++++--
>>  5 files changed, 51 insertions(+), 9 deletions(-)
>> 
>> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
>> index 2594fb647384..b76906914d89 100644
>> --- a/fs/xfs/libxfs/xfs_fs.h
>> +++ b/fs/xfs/libxfs/xfs_fs.h
>> @@ -394,7 +394,7 @@ struct xfs_bulkstat {
>>  	uint32_t	bs_extsize_blks; /* extent size hint, blocks	*/
>>  
>>  	uint32_t	bs_nlink;	/* number of links		*/
>> -	uint32_t	bs_extents;	/* number of extents		*/
>> +	uint32_t	bs_extents32;	/* 32-bit data fork extent counter */
>>  	uint32_t	bs_aextents;	/* attribute number of extents	*/
>>  	uint16_t	bs_version;	/* structure version		*/
>>  	uint16_t	bs_forkoff;	/* inode fork offset in bytes	*/
>
> I don't think renaming structure members is a good idea - it breaks
> the user API and forces applications to require source level
> modifications just to compile on both old and new xfsprogs installs.
>

Ok. I will revert the rename.

>> @@ -403,8 +403,9 @@ struct xfs_bulkstat {
>>  	uint16_t	bs_checked;	/* checked inode metadata	*/
>>  	uint16_t	bs_mode;	/* type and mode		*/
>>  	uint16_t	bs_pad2;	/* zeroed			*/
>> +	uint64_t	bs_extents64;	/* 64-bit data fork extent counter */
>>  
>> -	uint64_t	bs_pad[7];	/* zeroed			*/
>> +	uint64_t	bs_pad[6];	/* zeroed			*/
>>  };
>>  
>>  #define XFS_BULKSTAT_VERSION_V1	(1)
>> @@ -469,7 +470,8 @@ struct xfs_bulk_ireq {
>>  	uint32_t	icount;		/* I: count of entries in buffer */
>>  	uint32_t	ocount;		/* O: count of entries filled out */
>>  	uint32_t	agno;		/* I: see comment for IREQ_AGNO	*/
>> -	uint64_t	reserved[5];	/* must be zero			*/
>> +	uint64_t	bulkstat_flags; /* I: Bulkstat operation flags */
>> +	uint64_t	reserved[4];	/* must be zero			*/
>>  };
>>  
>>  /*
>> @@ -492,9 +494,16 @@ struct xfs_bulk_ireq {
>>   */
>>  #define XFS_BULK_IREQ_METADIR	(1 << 2)
>>  
>> -#define XFS_BULK_IREQ_FLAGS_ALL	(XFS_BULK_IREQ_AGNO | \
>> +#define XFS_BULK_IREQ_BULKSTAT	(1 << 3)
>> +
>> +#define XFS_BULK_IREQ_FLAGS_ALL	(XFS_BULK_IREQ_AGNO |	 \
>>  				 XFS_BULK_IREQ_SPECIAL | \
>> -				 XFS_BULK_IREQ_METADIR)
>> +				 XFS_BULK_IREQ_METADIR | \
>> +				 XFS_BULK_IREQ_BULKSTAT)
>
> What's this XFS_BULK_IREQ_METADIR thing? I haven't noticed that when
> scanning any recent proposed patch series....
>

XFS_BULK_IREQ_METADIR is from Darrick's tree. His "Kill XFS_BTREE_MAXLEVELS"
patch series is based on his other patchsets. His recent "xfs: support dynamic
btree cursor height" patch series rebases only the required patchset on top of
v5.15-rc1 kernel eliminating the others.

>> +#define XFS_BULK_IREQ_BULKSTAT_NREXT64 (1 << 0)
>> +
>> +#define XFS_BULK_IREQ_BULKSTAT_FLAGS_ALL (XFS_BULK_IREQ_BULKSTAT_NREXT64)
>
> As per above, this seems unnecessarily complex.
>
>> @@ -134,7 +136,26 @@ xfs_bulkstat_one_int(
>>  
>>  	buf->bs_xflags = xfs_ip2xflags(ip);
>>  	buf->bs_extsize_blks = ip->i_extsize;
>> -	buf->bs_extents = xfs_ifork_nextents(&ip->i_df);
>> +
>> +	nextents = xfs_ifork_nextents(&ip->i_df);
>> +	if (!(bc->breq->flags & XFS_IBULK_NREXT64)) {
>> +		xfs_extnum_t max_nextents = XFS_IFORK_EXTCNT_MAXS32;
>> +
>> +		if (unlikely(XFS_TEST_ERROR(false, mp,
>> +				XFS_ERRTAG_REDUCE_MAX_IEXTENTS)))
>> +			max_nextents = 10;
>> +
>> +		if (nextents > max_nextents) {
>> +			xfs_iunlock(ip, XFS_ILOCK_SHARED);
>> +			xfs_irele(ip);
>> +			error = -EINVAL;
>> +			goto out_advance;
>> +		}
>
> So we return an EINVAL error if any extent overflows the 32 bit
> counter? Why isn't this -EOVERFLOW?
>

Returning -EINVAL causes xfs_bulkstat_iwalk() to skip inodes whose extent
count is larger than that which can be fitted into a 32-bit field. Returning
-EOVERFLOW causes the bulkstat ioctl to stop reporting remaining inodes.

>> +		buf->bs_extents32 = nextents;
>> +	} else {
>> +		buf->bs_extents64 = nextents;
>> +	}
>> +
>>  	xfs_bulkstat_health(ip, buf);
>>  	buf->bs_aextents = xfs_ifork_nextents(ip->i_afp);
>>  	buf->bs_forkoff = XFS_IFORK_BOFF(ip);
>> @@ -356,7 +377,7 @@ xfs_bulkstat_to_bstat(
>>  	bs1->bs_blocks = bstat->bs_blocks;
>>  	bs1->bs_xflags = bstat->bs_xflags;
>>  	bs1->bs_extsize = XFS_FSB_TO_B(mp, bstat->bs_extsize_blks);
>> -	bs1->bs_extents = bstat->bs_extents;
>> +	bs1->bs_extents = bstat->bs_extents32;
>>  	bs1->bs_gen = bstat->bs_gen;
>>  	bs1->bs_projid_lo = bstat->bs_projectid & 0xFFFF;
>>  	bs1->bs_forkoff = bstat->bs_forkoff;
>> diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
>> index f5a13f69883a..f61685da3837 100644
>> --- a/fs/xfs/xfs_itable.h
>> +++ b/fs/xfs/xfs_itable.h
>> @@ -22,6 +22,8 @@ struct xfs_ibulk {
>>  /* Signal that we can return metadata directories. */
>>  #define XFS_IBULK_METADIR	(XFS_IWALK_METADIR)
>>  
>> +#define XFS_IBULK_NREXT64	(XFS_IWALK_NREXT64)
>> +
>>  /*
>>   * Advance the user buffer pointer by one record of the given size.  If the
>>   * buffer is now full, return the appropriate error code.
>> diff --git a/fs/xfs/xfs_iwalk.h b/fs/xfs/xfs_iwalk.h
>> index d7a082e45cbf..27a6842a1bb5 100644
>> --- a/fs/xfs/xfs_iwalk.h
>> +++ b/fs/xfs/xfs_iwalk.h
>> @@ -31,8 +31,11 @@ int xfs_iwalk_threaded(struct xfs_mount *mp, xfs_ino_t startino,
>>  /* Signal that we can return metadata directories. */
>>  #define XFS_IWALK_METADIR	(0x2)
>>  
>> -#define XFS_IWALK_FLAGS_ALL	(XFS_IWALK_SAME_AG | \
>> -				 XFS_IWALK_METADIR)
>> +#define XFS_IWALK_NREXT64	(0x4)
>
> Can we use '(1 << 2)' style notation for new bit field defines?

Sure, I will change this.

-- 
chandan