1 files changed, 51 insertions, 20 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5929cc5fc01f..c083a67d0091 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3343,36 +3343,67 @@ int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered)
 	return btrfs_finish_one_ordered(ordered);
 }
 
-void btrfs_calculate_block_csum(struct btrfs_fs_info *fs_info, phys_addr_t paddr,
-				u8 *dest)
+/*
+ * Calculate the checksum of an fs block at physical memory address @paddr,
+ * and save the result to @dest.
+ *
+ * The folio containing @paddr must be large enough to contain a full fs block.
+ */
+void btrfs_calculate_block_csum_folio(struct btrfs_fs_info *fs_info,
+				      const phys_addr_t paddr, u8 *dest)
 {
 	struct folio *folio = page_folio(phys_to_page(paddr));
 	const u32 blocksize = fs_info->sectorsize;
-	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+	const u32 step = min(blocksize, PAGE_SIZE);
+	const u32 nr_steps = blocksize / step;
+	phys_addr_t paddrs[BTRFS_MAX_BLOCKSIZE / PAGE_SIZE];
 
-	shash->tfm = fs_info->csum_shash;
 	/* The full block must be inside the folio. */
 	ASSERT(offset_in_folio(folio, paddr) + blocksize <= folio_size(folio));
 
-	if (folio_test_partial_kmap(folio)) {
-		size_t cur = paddr;
+	for (int i = 0; i < nr_steps; i++) {
+		u32 pindex = offset_in_folio(folio, paddr + i * step) >> PAGE_SHIFT;
 
-		crypto_shash_init(shash);
-		while (cur < paddr + blocksize) {
-			void *kaddr;
-			size_t len = min(paddr + blocksize - cur,
-					 PAGE_SIZE - offset_in_page(cur));
+		/*
+		 * For bs <= ps cases, we will only run the loop once, so the offset
+		 * inside the page will only added to paddrs[0].
+		 *
+		 * For bs > ps cases, the block must be page aligned, thus offset
+		 * inside the page will always be 0.
+		 */
+		paddrs[i] = page_to_phys(folio_page(folio, pindex)) + offset_in_page(paddr);
+	}
+	return btrfs_calculate_block_csum_pages(fs_info, paddrs, dest);
+}
 
-			kaddr = kmap_local_folio(folio, offset_in_folio(folio, cur));
-			crypto_shash_update(shash, kaddr, len);
-			kunmap_local(kaddr);
-			cur += len;
-		}
-		crypto_shash_final(shash, dest);
-	} else {
-		crypto_shash_digest(shash, phys_to_virt(paddr), blocksize, dest);
+/*
+ * Calculate the checksum of a fs block backed by multiple noncontiguous pages
+ * at @paddrs[] and save the result to @dest.
+ *
+ * The folio containing @paddr must be large enough to contain a full fs block.
+ */
+void btrfs_calculate_block_csum_pages(struct btrfs_fs_info *fs_info,
+				      const phys_addr_t paddrs[], u8 *dest)
+{
+	const u32 blocksize = fs_info->sectorsize;
+	const u32 step = min(blocksize, PAGE_SIZE);
+	const u32 nr_steps = blocksize / step;
+	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+
+	shash->tfm = fs_info->csum_shash;
+	crypto_shash_init(shash);
+	for (int i = 0; i < nr_steps; i++) {
+		const phys_addr_t paddr = paddrs[i];
+		void *kaddr;
+
+		ASSERT(offset_in_page(paddr) + step <= PAGE_SIZE);
+		kaddr = kmap_local_page(phys_to_page(paddr)) + offset_in_page(paddr);
+		crypto_shash_update(shash, kaddr, step);
+		kunmap_local(kaddr);
 	}
+	crypto_shash_final(shash, dest);
 }
+
 /*
  * Verify the checksum for a single sector without any extra action that depend
  * on the type of I/O.
@@ -3382,7 +3413,7 @@ void btrfs_calculate_block_csum(struct btrfs_fs_info *fs_info, phys_addr_t paddr
 int btrfs_check_block_csum(struct btrfs_fs_info *fs_info, phys_addr_t paddr, u8 *csum,
 			   const u8 * const csum_expected)
 {
-	btrfs_calculate_block_csum(fs_info, paddr, csum);
+	btrfs_calculate_block_csum_folio(fs_info, paddr, csum);
 	if (unlikely(memcmp(csum, csum_expected, fs_info->csum_size) != 0))
 		return -EIO;
 	return 0;