eCryptfs: track header bytes rather than extents

Remove internal references to header extents; just keep track of header bytes
instead.  Headers can easily span multiple pages with the recent persistent
file changes.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 9a5e0d17f1c5..dc74b186145d 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -100,13 +100,14 @@ static void set_header_info(char *page_virt,
                             struct ecryptfs_crypt_stat *crypt_stat)
 {
         size_t written;
-        int save_num_header_extents_at_front =
-                crypt_stat->num_header_extents_at_front;
+        size_t save_num_header_bytes_at_front =
+                crypt_stat->num_header_bytes_at_front;
 
-        crypt_stat->num_header_extents_at_front = 1;
+        crypt_stat->num_header_bytes_at_front =
+                ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
-        crypt_stat->num_header_extents_at_front =
-                save_num_header_extents_at_front;
+        crypt_stat->num_header_bytes_at_front =
+                save_num_header_bytes_at_front;
 }
 
 /**
@@ -132,8 +133,11 @@ ecryptfs_copy_up_encrypted_with_header(struct page *page,
                 loff_t view_extent_num = ((((loff_t)page->index)
                                            * num_extents_per_page)
                                           + extent_num_in_page);
+                size_t num_header_extents_at_front =
+                        (crypt_stat->num_header_bytes_at_front
+                         / crypt_stat->extent_size);
 
-                if (view_extent_num < crypt_stat->num_header_extents_at_front) {
+                if (view_extent_num < num_header_extents_at_front) {
                         /* This is a header extent */
                         char *page_virt;
 
@@ -155,9 +159,8 @@ ecryptfs_copy_up_encrypted_with_header(struct page *page,
                 } else {
                         /* This is an encrypted data extent */
                         loff_t lower_offset =
-                                ((view_extent_num -
-                                  crypt_stat->num_header_extents_at_front)
-                                 * crypt_stat->extent_size);
+                                ((view_extent_num * crypt_stat->extent_size)
+                                 - crypt_stat->num_header_bytes_at_front);
 
                         rc = ecryptfs_read_lower_page_segment(
                                 page, (lower_offset >> PAGE_CACHE_SHIFT),