Re: [PATCH v3 6/7] xfs: Add RT atomic write unit max to xfs_mount

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Jan 02, 2025 at 02:04:10PM +0000, John Garry wrote:
> rtvol guarantees alloc unit alignment through rt_extsize. As such, it is
> possible to atomically write multiple FS blocks in a rtvol (up to
> rt_extsize).
> 
> Add a member to xfs_mount to hold the pre-calculated atomic write unit max.
> 
> The value in rt_extsize is not necessarily a power-of-2, so find the
> largest power-of-2 evenly divisible into rt_extsize.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>

I guess that works.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_sb.c |  3 +++
>  fs/xfs/xfs_mount.h     |  1 +
>  fs/xfs/xfs_rtalloc.c   | 23 +++++++++++++++++++++++
>  fs/xfs/xfs_rtalloc.h   |  4 ++++
>  4 files changed, 31 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
> index 3b5623611eba..6381060df901 100644
> --- a/fs/xfs/libxfs/xfs_sb.c
> +++ b/fs/xfs/libxfs/xfs_sb.c
> @@ -25,6 +25,7 @@
>  #include "xfs_da_format.h"
>  #include "xfs_health.h"
>  #include "xfs_ag.h"
> +#include "xfs_rtalloc.h"
>  #include "xfs_rtbitmap.h"
>  #include "xfs_exchrange.h"
>  #include "xfs_rtgroup.h"
> @@ -1149,6 +1150,8 @@ xfs_sb_mount_rextsize(
>  		rgs->blklog = 0;
>  		rgs->blkmask = (uint64_t)-1;
>  	}
> +
> +	xfs_rt_awu_update(mp);
>  }
>  
>  /* Update incore sb rt extent size, then recompute the cached rt geometry. */
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index db9dade7d22a..f2f1d2c667cc 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -191,6 +191,7 @@ typedef struct xfs_mount {
>  	bool			m_fail_unmount;
>  	bool			m_finobt_nores; /* no per-AG finobt resv. */
>  	bool			m_update_sb;	/* sb needs update in mount */
> +	xfs_extlen_t		m_rt_awu_max;   /* rt atomic write unit max */
>  
>  	/*
>  	 * Bitsets of per-fs metadata that have been checked and/or are sick.
> diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
> index fcfa6e0eb3ad..e3093f3c7670 100644
> --- a/fs/xfs/xfs_rtalloc.c
> +++ b/fs/xfs/xfs_rtalloc.c
> @@ -735,6 +735,28 @@ xfs_rtginode_ensure(
>  	return xfs_rtginode_create(rtg, type, true);
>  }
>  
> +void
> +xfs_rt_awu_update(
> +	struct xfs_mount	*mp)
> +{
> +	xfs_agblock_t		rsize = mp->m_sb.sb_rextsize;
> +	xfs_extlen_t		awu_max;
> +
> +	if (is_power_of_2(rsize)) {
> +		mp->m_rt_awu_max = rsize;
> +		return;
> +	}
> +
> +	/* Find highest power-of-2 evenly divisible into sb_rextsize */
> +	awu_max = 1;
> +	while (1) {
> +		if (rsize % (awu_max * 2))
> +			break;
> +		awu_max *= 2;
> +	}
> +	mp->m_rt_awu_max = awu_max;
> +}
> +
>  static struct xfs_mount *
>  xfs_growfs_rt_alloc_fake_mount(
>  	const struct xfs_mount	*mp,
> @@ -969,6 +991,7 @@ xfs_growfs_rt_bmblock(
>  	 */
>  	mp->m_rsumlevels = nmp->m_rsumlevels;
>  	mp->m_rsumblocks = nmp->m_rsumblocks;
> +	mp->m_rt_awu_max = nmp->m_rt_awu_max;
>  
>  	/*
>  	 * Recompute the growfsrt reservation from the new rsumsize.
> diff --git a/fs/xfs/xfs_rtalloc.h b/fs/xfs/xfs_rtalloc.h
> index 8e2a07b8174b..fcb7bb3df470 100644
> --- a/fs/xfs/xfs_rtalloc.h
> +++ b/fs/xfs/xfs_rtalloc.h
> @@ -42,6 +42,10 @@ xfs_growfs_rt(
>  	struct xfs_mount	*mp,	/* file system mount structure */
>  	xfs_growfs_rt_t		*in);	/* user supplied growfs struct */
>  
> +void
> +xfs_rt_awu_update(
> +	struct xfs_mount	*mp);
> +
>  int xfs_rtalloc_reinit_frextents(struct xfs_mount *mp);
>  #else
>  # define xfs_growfs_rt(mp,in)				(-ENOSYS)
> -- 
> 2.31.1
> 
>