eCryptfs: Simplify lower file offset calculation

Now that lower filesystem IO operations occur for complete
PAGE_CACHE_SIZE bytes, the calculation for converting an eCryptfs extent
index into a lower file offset can be simplified.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

1 files changed, 7 insertions, 11 deletions

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 4185584594f5..3547708fb4e1 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -407,15 +407,15 @@ out:
 }
 
 /**
- * ecryptfs_lower_offset_for_extent
+ * lower_offset_for_page
  *
  * Convert an eCryptfs page index into a lower byte offset
  */
-static void ecryptfs_lower_offset_for_extent(loff_t *offset, loff_t extent_num,
-                                             struct ecryptfs_crypt_stat *crypt_stat)
+static loff_t lower_offset_for_page(struct ecryptfs_crypt_stat *crypt_stat,
+                                    struct page *page)
 {
-        (*offset) = ecryptfs_lower_header_size(crypt_stat)
-                    + (crypt_stat->extent_size * extent_num);
+        return ecryptfs_lower_header_size(crypt_stat) +
+               (page->index << PAGE_CACHE_SHIFT);
 }
 
 /**
@@ -517,9 +517,7 @@ int ecryptfs_encrypt_page(struct page *page)
                 }
         }
 
-        ecryptfs_lower_offset_for_extent(&lower_offset,
-                page->index * (PAGE_CACHE_SIZE / crypt_stat->extent_size),
-                crypt_stat);
+        lower_offset = lower_offset_for_page(crypt_stat, page);
         enc_extent_virt = kmap(enc_extent_page);
         rc = ecryptfs_write_lower(ecryptfs_inode, enc_extent_virt, lower_offset,
                                   PAGE_CACHE_SIZE);
@@ -612,9 +610,7 @@ int ecryptfs_decrypt_page(struct page *page)
                 goto out;
         }
 
-        ecryptfs_lower_offset_for_extent(&lower_offset,
-                page->index * (PAGE_CACHE_SIZE / crypt_stat->extent_size),
-                crypt_stat);
+        lower_offset = lower_offset_for_page(crypt_stat, page);
         enc_extent_virt = kmap(enc_extent_page);
         rc = ecryptfs_read_lower(enc_extent_virt, lower_offset, PAGE_CACHE_SIZE,
                                  ecryptfs_inode);