Re: [PATCH v2] xfs: add write pointer to xfs_rtgroup_geometry

Darrick J. Wong
2026-03-02T16:25:59Z

On Sun, Mar 01, 2026 at 10:34:35AM +1000, Wilfred Mallawa wrote:
> From: Wilfred Mallawa <wilfred.mallawa@wdc.com>
>
> There is currently no XFS ioctl that allows userspace to retrieve the
> write pointer for a specific realtime group block for zoned XFS. On zoned
> block devices, userspace can obtain this information via zone reports from
> the underlying device. However, for zoned XFS operating on regular block
> devices, no equivalent mechanism exists.
>
> Access to the realtime group write pointer is useful to userspace
> development and analysis tools such as Zonar [1]. So extend the existing
> struct xfs_rtgroup_geometry to add a new rg_writepointer field. This field
> is valid if XFS_RTGROUP_GEOM_WRITEPOINTER flag is set. The rg_writepointer
> field specifies the location of the current writepointer as a block offset
> into the respective rtgroup.
>
> [1] https://lwn.net/Articles/1059364/
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
> ---
> V1 -> V2:
> - Use a __u32 to instead of __u64 to store the write pointer
> - This, also drop the previously added padding.
> - Directly retun the writepointer block instead of converting
> with XFS_FSB_TO_BB(), for consistentcy in struct
> xfs_rtgroup_geometry (i.e rg_length is in fs blocks).

Hey, that looks better now. Thanks for the patch!
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/xfs/libxfs/xfs_fs.h | 5 ++++-
> fs/xfs/xfs_ioctl.c | 19 +++++++++++++++++++
> 2 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index d165de607d17..185f09f327c0 100644
> --- a/fs/xfs/libxfs/xfs_fs.h
> +++ b/fs/xfs/libxfs/xfs_fs.h
> @@ -995,7 +995,8 @@ struct xfs_rtgroup_geometry {
> __u32 rg_sick; /* o: sick things in ag */
> __u32 rg_checked; /* o: checked metadata in ag */
> __u32 rg_flags; /* i/o: flags for this ag */
> - __u32 rg_reserved[27]; /* o: zero */
> + __u32 rg_writepointer; /* o: write pointer block offset for zoned */
> + __u32 rg_reserved[26]; /* o: zero */
> };
> #define XFS_RTGROUP_GEOM_SICK_SUPER (1U << 0) /* superblock */
> #define XFS_RTGROUP_GEOM_SICK_BITMAP (1U << 1) /* rtbitmap */
> @@ -1003,6 +1004,8 @@ struct xfs_rtgroup_geometry {
> #define XFS_RTGROUP_GEOM_SICK_RMAPBT (1U << 3) /* reverse mappings */
> #define XFS_RTGROUP_GEOM_SICK_REFCNTBT (1U << 4) /* reference counts */
>
> +#define XFS_RTGROUP_GEOM_WRITEPOINTER (1U << 0) /* write pointer */
> +
> /* Health monitor event domains */
>
> /* affects the whole fs */
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index facffdc8dca8..46e234863644 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -37,12 +37,15 @@
> #include "xfs_ioctl.h"
> #include "xfs_xattr.h"
> #include "xfs_rtbitmap.h"
> +#include "xfs_rtrmap_btree.h"
> #include "xfs_file.h"
> #include "xfs_exchrange.h"
> #include "xfs_handle.h"
> #include "xfs_rtgroup.h"
> #include "xfs_healthmon.h"
> #include "xfs_verify_media.h"
> +#include "xfs_zone_priv.h"
> +#include "xfs_zone_alloc.h"
>
> #include <linux/mount.h>
> #include <linux/fileattr.h>
> @@ -413,6 +416,7 @@ xfs_ioc_rtgroup_geometry(
> {
> struct xfs_rtgroup *rtg;
> struct xfs_rtgroup_geometry rgeo;
> + xfs_rgblock_t highest_rgbno;
> int error;
>
> if (copy_from_user(&rgeo, arg, sizeof(rgeo)))
> @@ -433,6 +437,21 @@ xfs_ioc_rtgroup_geometry(
> if (error)
> return error;
>
> + if (xfs_has_zoned(mp)) {
> + xfs_rtgroup_lock(rtg, XFS_RTGLOCK_RMAP);
> + if (rtg->rtg_open_zone) {
> + rgeo.rg_writepointer = rtg->rtg_open_zone->oz_allocated;
> + } else {
> + highest_rgbno = xfs_rtrmap_highest_rgbno(rtg);
> + if (highest_rgbno == NULLRGBLOCK)
> + rgeo.rg_writepointer = 0;
> + else
> + rgeo.rg_writepointer = highest_rgbno + 1;
> + }
> + xfs_rtgroup_unlock(rtg, XFS_RTGLOCK_RMAP);
> + rgeo.rg_flags |= XFS_RTGROUP_GEOM_WRITEPOINTER;
> + }
> +
> if (copy_to_user(arg, &rgeo, sizeof(rgeo)))
> return -EFAULT;
> return 0;
> --
> 2.53.0
>
>