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

Dave Chinner
2021-09-27T23:06:41Z

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@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.

> @@ -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@fromorbit.com