+/**
+ * ecryptfs_lower_offset_for_extent
+ *
+ * Convert an eCryptfs page index into a lower byte offset
+ */
+void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
+ struct ecryptfs_crypt_stat *crypt_stat)
+{
+ (*offset) = ((crypt_stat->extent_size
+ * crypt_stat->num_header_extents_at_front)
+ + (crypt_stat->extent_size * extent_num));
+}
+
+/**
+ * ecryptfs_encrypt_extent
+ * @enc_extent_page: Allocated page into which to encrypt the data in
+ * @page
+ * @crypt_stat: crypt_stat containing cryptographic context for the
+ * encryption operation
+ * @page: Page containing plaintext data extent to encrypt
+ * @extent_offset: Page extent offset for use in generating IV
+ *
+ * Encrypts one extent of data.
+ *
+ * Return zero on success; non-zero otherwise
+ */
+static int ecryptfs_encrypt_extent(struct page *enc_extent_page,
+ struct ecryptfs_crypt_stat *crypt_stat,
+ struct page *page,
+ unsigned long extent_offset)
+{
+ unsigned long extent_base;
+ char extent_iv[ECRYPTFS_MAX_IV_BYTES];
+ int rc;
+
+ extent_base = (page->index
+ * (PAGE_CACHE_SIZE / crypt_stat->extent_size));
+ rc = ecryptfs_derive_iv(extent_iv, crypt_stat,
+ (extent_base + extent_offset));
+ if (rc) {
+ ecryptfs_printk(KERN_ERR, "Error attempting to "
+ "derive IV for extent [0x%.16x]; "
+ "rc = [%d]\n", (extent_base + extent_offset),
+ rc);
+ goto out;
+ }
+ if (unlikely(ecryptfs_verbosity > 0)) {
+ ecryptfs_printk(KERN_DEBUG, "Encrypting extent "
+ "with iv:\n");
+ ecryptfs_dump_hex(extent_iv, crypt_stat->iv_bytes);
+ ecryptfs_printk(KERN_DEBUG, "First 8 bytes before "
+ "encryption:\n");
+ ecryptfs_dump_hex((char *)
+ (page_address(page)
+ + (extent_offset * crypt_stat->extent_size)),
+ 8);
+ }
+ rc = ecryptfs_encrypt_page_offset(crypt_stat, enc_extent_page, 0,
+ page, (extent_offset
+ * crypt_stat->extent_size),
+ crypt_stat->extent_size, extent_iv);
+ if (rc < 0) {
+ printk(KERN_ERR "%s: Error attempting to encrypt page with "
+ "page->index = [%ld], extent_offset = [%ld]; "
+ "rc = [%d]\n", __FUNCTION__, page->index, extent_offset,
+ rc);
+ goto out;
+ }
+ rc = 0;
+ if (unlikely(ecryptfs_verbosity > 0)) {
+ ecryptfs_printk(KERN_DEBUG, "Encrypt extent [0x%.16x]; "
+ "rc = [%d]\n", (extent_base + extent_offset),
+ rc);
+ ecryptfs_printk(KERN_DEBUG, "First 8 bytes after "
+ "encryption:\n");
+ ecryptfs_dump_hex((char *)(page_address(enc_extent_page)), 8);
+ }
+out:
+ return rc;
+}
+