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

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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?

> Suggested-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx>
> ---
>  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.

> @@ -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....

> +#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?

> +		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?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx



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