eCryptfs: Decrypt pages in-place

When reading in a page, eCryptfs would allocate a helper page, fill it with encrypted data from the lower filesytem, and then decrypt the data from the encrypted page and store the result in the eCryptfs page cache page. The crypto API supports in-place crypto operations which means that the allocation of the helper page is unnecessary when decrypting. This patch gets rid of the unneeded page allocation by reading encrypted data from the lower filesystem directly into the page cache page. The page cache page is then decrypted in-place. Signed-off-by: Tyler Hicks <[email protected]>
jledet · Jun 8, 2013 · 9c6043f · 9c6043f
1 parent 28916d1
commit 9c6043f
Showing 1 changed file with 5 additions and 16 deletions.
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
@@ -586,8 +586,7 @@ int ecryptfs_decrypt_page(struct page *page)
 {
 	struct inode *ecryptfs_inode;
 	struct ecryptfs_crypt_stat *crypt_stat;
-	char *enc_extent_virt;
-	struct page *enc_extent_page = NULL;
+	char *page_virt;
 	unsigned long extent_offset;
 	loff_t lower_offset;
 	int rc = 0;
@@ -596,19 +595,12 @@ int ecryptfs_decrypt_page(struct page *page)
 	crypt_stat =
 		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
 	BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
-	enc_extent_page = alloc_page(GFP_USER);
-	if (!enc_extent_page) {
-		rc = -ENOMEM;
-		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
-				"encrypted extent\n");
-		goto out;
-	}
 
 	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,
+	page_virt = kmap(page);
+	rc = ecryptfs_read_lower(page_virt, lower_offset, PAGE_CACHE_SIZE,
 				 ecryptfs_inode);
-	kunmap(enc_extent_page);
+	kunmap(page);
 	if (rc < 0) {
 		ecryptfs_printk(KERN_ERR,
 			"Error attempting to read lower page; rc = [%d]\n",
@@ -619,7 +611,7 @@ int ecryptfs_decrypt_page(struct page *page)
 	for (extent_offset = 0;
 	     extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
 	     extent_offset++) {
-		rc = ecryptfs_decrypt_extent(page, crypt_stat, enc_extent_page,
+		rc = ecryptfs_decrypt_extent(page, crypt_stat, page,
 					     extent_offset);
 		if (rc) {
 			printk(KERN_ERR "%s: Error encrypting extent; "
@@ -628,9 +620,6 @@ int ecryptfs_decrypt_page(struct page *page)
 		}
 	}
 out:
-	if (enc_extent_page) {
-		__free_page(enc_extent_page);
-	}
 	return rc;
 }