eCryptfs: read_write.c routines

Add a set of functions through which all I/O to lower files is consolidated.
This patch adds a new inode_info reference to a persistent lower file for each
eCryptfs inode; another patch later in this series will set that up.  This
persistent lower file is what the read_write.c functions use to call
vfs_read() and vfs_write() on the lower filesystem, so even when reads and
writes come in through aops->readpage and aops->writepage, we can satisfy them
without resorting to direct access to the lower inode's address space.
Several function declarations are going to be changing with this patchset.
For now, in order to keep from breaking the build, I am putting dummy
parameters in for those functions.

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>

fs/ecryptfs/Makefile

@@ -4,4 +4,4 @@
 
 obj-$(CONFIG_ECRYPT_FS) += ecryptfs.o
 
-ecryptfs-objs := dentry.o file.o inode.o main.o super.o mmap.o crypto.o keystore.o messaging.o netlink.o debug.o
+ecryptfs-objs := dentry.o file.o inode.o main.o super.o mmap.o read_write.o crypto.o keystore.o messaging.o netlink.o debug.o

fs/ecryptfs/ecryptfs_kernel.h

@@ -260,6 +260,8 @@ struct ecryptfs_crypt_stat {
 struct ecryptfs_inode_info {
 	struct inode vfs_inode;
 	struct inode *wii_inode;
+	struct file *lower_file;
+	struct mutex lower_file_mutex;
 	struct ecryptfs_crypt_stat crypt_stat;
 };
 
@@ -653,5 +655,21 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
 				      char *sig);
 int ecryptfs_write_zeros(struct file *file, pgoff_t index, int start,
 			 int num_zeros);
+int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
+			 loff_t offset, size_t size);
+int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
+				      struct page *page_for_lower,
+				      size_t offset_in_page, size_t size);
+int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
+		   size_t size);
+int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
+			struct inode *ecryptfs_inode);
+int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
+				     pgoff_t page_index,
+				     size_t offset_in_page, size_t size,
+				     struct inode *ecryptfs_inode);
+int ecryptfs_read(char *data, loff_t offset, size_t size,
+		  struct file *ecryptfs_file);
+struct page *ecryptfs_get1page(struct file *file, loff_t index);
 
 #endif /* #ifndef ECRYPTFS_KERNEL_H */

fs/ecryptfs/mmap.c

@@ -44,7 +44,7 @@ struct kmem_cache *ecryptfs_lower_page_cache;
  * Returns unlocked and up-to-date page (if ok), with increased
  * refcnt.
  */
-static struct page *ecryptfs_get1page(struct file *file, int index)
+struct page *ecryptfs_get1page(struct file *file, loff_t index)
 {
 	struct dentry *dentry;
 	struct inode *inode;