Re: [PATCH v4 04/25] fsverity: introduce fsverity_folio_zero_hash()

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

On Mon, Mar 09, 2026 at 08:23:19PM +0100, Andrey Albershteyn wrote:
> Helper to pre-fill folio with hashes of empty blocks. This will be used
> by iomap to synthesize blocks full of zero hashes on the fly.
> 
> Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>

Looks good to me,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/verity/pagecache.c    | 22 ++++++++++++++++++++++
>  include/linux/fsverity.h |  2 ++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c
> index 1819314ecaa3..1d94bf73f38c 100644
> --- a/fs/verity/pagecache.c
> +++ b/fs/verity/pagecache.c
> @@ -2,6 +2,7 @@
>  /*
>   * Copyright 2019 Google LLC
>   */
> +#include "fsverity_private.h"
>  
>  #include <linux/export.h>
>  #include <linux/fsverity.h>
> @@ -56,3 +57,24 @@ void generic_readahead_merkle_tree(struct inode *inode, pgoff_t index,
>  		folio_put(folio);
>  }
>  EXPORT_SYMBOL_GPL(generic_readahead_merkle_tree);
> +
> +/**
> + * fsverity_folio_zero_hash() - fill folio with hashes of zero data block
> + * @folio:	folio to fill
> + * @poff:	offset in the folio to start
> + * @plen:	length of the range to fill with hashes
> + * @vi:		fsverity info
> + */
> +void fsverity_folio_zero_hash(struct folio *folio, size_t poff, size_t plen,
> +			      struct fsverity_info *vi)
> +{
> +	size_t offset = poff;
> +
> +	WARN_ON_ONCE(!IS_ALIGNED(poff, vi->tree_params.digest_size));
> +	WARN_ON_ONCE(!IS_ALIGNED(plen, vi->tree_params.digest_size));
> +
> +	for (; offset < (poff + plen); offset += vi->tree_params.digest_size)
> +		memcpy_to_folio(folio, offset, vi->tree_params.zero_digest,
> +				vi->tree_params.digest_size);
> +}
> +EXPORT_SYMBOL_GPL(fsverity_folio_zero_hash);
> diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
> index 8ba7806b225e..b490b2c8a393 100644
> --- a/include/linux/fsverity.h
> +++ b/include/linux/fsverity.h
> @@ -321,5 +321,7 @@ void fsverity_cleanup_inode(struct inode *inode);
>  struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index);
>  void generic_readahead_merkle_tree(struct inode *inode, pgoff_t index,
>  				   unsigned long nr_pages);
> +void fsverity_folio_zero_hash(struct folio *folio, size_t poff, size_t plen,
> +			      struct fsverity_info *vi);
>  
>  #endif	/* _LINUX_FSVERITY_H */
> -- 
> 2.51.2
> 
>