Re: [PATCH RFC 21/29] xfs: add writeback and iomap reading of Merkel tree pages

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

> Subject: [PATCH RFC 21/29] xfs: add writeback and iomap reading of Merkel tree pages

s/Merkel/Merkle/

On Mon, Jul 28, 2025 at 10:30:25PM +0200, Andrey Albershteyn wrote:
> In the writeback path use unbound write interface, meaning that inode
> size is not updated and none of the file size checks are applied.
> 
> In read path let iomap know that data is stored beyond EOF via flag.
> This leads to skipping of post EOF zeroing.
> 
> Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
> ---
>  fs/xfs/xfs_aops.c  | 21 ++++++++++++++-------
>  fs/xfs/xfs_iomap.c |  9 +++++++--
>  2 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 63151feb9c3f..02e2c04b36c1 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -22,6 +22,7 @@
>  #include "xfs_icache.h"
>  #include "xfs_zone_alloc.h"
>  #include "xfs_rtgroup.h"
> +#include "xfs_fsverity.h"
>  
>  struct xfs_writepage_ctx {
>  	struct iomap_writepage_ctx ctx;
> @@ -628,10 +629,12 @@ static const struct iomap_writeback_ops xfs_zoned_writeback_ops = {
>  
>  STATIC int
>  xfs_vm_writepages(
> -	struct address_space	*mapping,
> -	struct writeback_control *wbc)
> +	struct address_space		*mapping,
> +	struct writeback_control	*wbc)
>  {
> -	struct xfs_inode	*ip = XFS_I(mapping->host);
> +	struct xfs_inode		*ip = XFS_I(mapping->host);
> +	struct xfs_writepage_ctx	wpc = { };
> +
>  
>  	xfs_iflags_clear(ip, XFS_ITRUNCATED);
>  
> @@ -644,12 +647,16 @@ xfs_vm_writepages(
>  		if (xc.open_zone)
>  			xfs_open_zone_put(xc.open_zone);
>  		return error;
> -	} else {
> -		struct xfs_writepage_ctx	wpc = { };
> +	}
>  
> -		return iomap_writepages(mapping, wbc, &wpc.ctx,
> -				&xfs_writeback_ops);
> +	if (xfs_iflags_test(ip, XFS_VERITY_CONSTRUCTION)) {
> +		wbc->range_start = XFS_FSVERITY_MTREE_OFFSET;

Where is XFS_FSVERITY_MTREE_OFFSET defined?

(Oh, the next patch)

Do you need to update wbc->nr if you change range_start?

--D

> +		wbc->range_end = LLONG_MAX;
> +		return iomap_writepages_unbound(mapping, wbc, &wpc.ctx,
> +						&xfs_writeback_ops);
>  	}
> +
> +	return iomap_writepages(mapping, wbc, &wpc.ctx, &xfs_writeback_ops);
>  }
>  
>  STATIC int
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 00ec1a738b39..c8725508165c 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -2031,6 +2031,7 @@ xfs_read_iomap_begin(
>  	bool			shared = false;
>  	unsigned int		lockmode = XFS_ILOCK_SHARED;
>  	u64			seq;
> +	int			iomap_flags;
>  
>  	ASSERT(!(flags & (IOMAP_WRITE | IOMAP_ZERO)));
>  
> @@ -2050,8 +2051,12 @@ xfs_read_iomap_begin(
>  	if (error)
>  		return error;
>  	trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
> -	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags,
> -				 shared ? IOMAP_F_SHARED : 0, seq);
> +	iomap_flags = shared ? IOMAP_F_SHARED : 0;
> +
> +	if (fsverity_active(inode) && offset >= XFS_FSVERITY_MTREE_OFFSET)
> +		iomap_flags |= IOMAP_F_BEYOND_EOF;
> +
> +	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, iomap_flags, seq);
>  }
>  
>  const struct iomap_ops xfs_read_iomap_ops = {
> 
> -- 
> 2.50.0
> 
>