fs-verity: use memcpy_from_page()

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>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Link: https://lore.kernel.org/r/20220818223903.43710-1-ebiggers@kernel.org

diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index 14e2fb49cff561a9a16ffa71539c0e340fe67e92..bde8c9b7d25f64b9fde4196b02df5679b88ae809 100644 (file)
--- 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 @@ descend:
                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",