[PATCH] fs-verity: use memcpy_from_page()

[PATCH] fs-verity: use memcpy_from_page()

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Replace extract_hash() with the memcpy_from_page() helper function.

This is simpler, and it has the side effect of replacing the use of
kmap_atomic() with its recommended replacement kmap_local_page().

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/verity/verify.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index 14e2fb49cff561..bde8c9b7d25f64 100644
--- a/fs/verity/verify.c
+++ b/fs/verity/verify.c
@@ -39,16 +39,6 @@ static void hash_at_level(const struct merkle_tree_params *params,
 		   (params->log_blocksize - params->log_arity);
 }
 
-/* Extract a hash from a hash page */
-static void extract_hash(struct page *hpage, unsigned int hoffset,
-			 unsigned int hsize, u8 *out)
-{
-	void *virt = kmap_atomic(hpage);
-
-	memcpy(out, virt + hoffset, hsize);
-	kunmap_atomic(virt);
-}
-
 static inline int cmp_hashes(const struct fsverity_info *vi,
 			     const u8 *want_hash, const u8 *real_hash,
 			     pgoff_t index, int level)
@@ -129,7 +119,7 @@ static bool verify_page(struct inode *inode, const struct fsverity_info *vi,
 		}
 
 		if (PageChecked(hpage)) {
-			extract_hash(hpage, hoffset, hsize, _want_hash);
+			memcpy_from_page(_want_hash, hpage, hoffset, hsize);
 			want_hash = _want_hash;
 			put_page(hpage);
 			pr_debug_ratelimited("Hash page already checked, want %s:%*phN\n",
@@ -158,7 +148,7 @@ static bool verify_page(struct inode *inode, const struct fsverity_info *vi,
 		if (err)
 			goto out;
 		SetPageChecked(hpage);
-		extract_hash(hpage, hoffset, hsize, _want_hash);
+		memcpy_from_page(_want_hash, hpage, hoffset, hsize);
 		want_hash = _want_hash;
 		put_page(hpage);
 		pr_debug("Verified hash page at level %d, now want %s:%*phN\n",

base-commit: 568035b01cfb107af8d2e4bd2fb9aea22cf5b868
-- 
2.37.1

Re: [PATCH] fs-verity: use memcpy_from_page()

[Fabio M. De Francesco]

On Friday, August 19, 2022 12:39:03 AM CEST Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Replace extract_hash() with the memcpy_from_page() helper function.
> 
> This is simpler, and it has the side effect of replacing the use of
> kmap_atomic() with its recommended replacement kmap_local_page().
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/verity/verify.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 

It looks good to me...

Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Thanks,

Fabio

> diff --git a/fs/verity/verify.c b/fs/verity/verify.c
> index 14e2fb49cff561..bde8c9b7d25f64 100644
> --- a/fs/verity/verify.c
> +++ b/fs/verity/verify.c
> @@ -39,16 +39,6 @@ static void hash_at_level(const struct merkle_tree_params 
*params,
>  		   (params->log_blocksize - params->log_arity);
>  }
>  
> -/* Extract a hash from a hash page */
> -static void extract_hash(struct page *hpage, unsigned int hoffset,
> -			 unsigned int hsize, u8 *out)
> -{
> -	void *virt = kmap_atomic(hpage);
> -
> -	memcpy(out, virt + hoffset, hsize);
> -	kunmap_atomic(virt);
> -}
> -
>  static inline int cmp_hashes(const struct fsverity_info *vi,
>  			     const u8 *want_hash, const u8 
*real_hash,
>  			     pgoff_t index, int level)
> @@ -129,7 +119,7 @@ static bool verify_page(struct inode *inode, const 
struct fsverity_info *vi,
>  		}
>  
>  		if (PageChecked(hpage)) {
> -			extract_hash(hpage, hoffset, hsize, 
_want_hash);
> +			memcpy_from_page(_want_hash, hpage, hoffset, 
hsize);
>  			want_hash = _want_hash;
>  			put_page(hpage);
>  			pr_debug_ratelimited("Hash page already 
checked, want %s:%*phN\n",
> @@ -158,7 +148,7 @@ static bool verify_page(struct inode *inode, const 
struct fsverity_info *vi,
>  		if (err)
>  			goto out;
>  		SetPageChecked(hpage);
> -		extract_hash(hpage, hoffset, hsize, _want_hash);
> +		memcpy_from_page(_want_hash, hpage, hoffset, hsize);
>  		want_hash = _want_hash;
>  		put_page(hpage);
>  		pr_debug("Verified hash page at level %d, now want %s:
%*phN\n",
> 
> base-commit: 568035b01cfb107af8d2e4bd2fb9aea22cf5b868
> -- 
> 2.37.1
> 
>