From: Frank Swiderski <fes@chromium.org>
Date: Mon, 15 Nov 2010 18:43:22 +0000 (-0800)
Subject: ecryptfs: remove unnecessary decrypt when extending a file
X-Git-Tag: firefly_0821_release~7613^2~2663^2
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=24562486be76cf223b8d911f45e1d26eb3364b13;p=firefly-linux-kernel-4.4.55.git

ecryptfs: remove unnecessary decrypt when extending a file

Removes an unecessary page decrypt from ecryptfs_begin_write when the
page is beyond the current file size. Previously, the call to
ecryptfs_decrypt_page would result in a read of 0 bytes, but still
attempt to decrypt an entire page. This patch detects that case and
merely zeros the page before marking it up-to-date.

Signed-off-by: Frank Swiderski <fes@chromium.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
---

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 4b9011392736..cc64fca89f8d 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -290,6 +290,7 @@ static int ecryptfs_write_begin(struct file *file,
 		return -ENOMEM;
 	*pagep = page;
 
+	prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 	if (!PageUptodate(page)) {
 		struct ecryptfs_crypt_stat *crypt_stat =
 			&ecryptfs_inode_to_private(mapping->host)->crypt_stat;
@@ -335,18 +336,23 @@ static int ecryptfs_write_begin(struct file *file,
 				SetPageUptodate(page);
 			}
 		} else {
-			rc = ecryptfs_decrypt_page(page);
-			if (rc) {
-				printk(KERN_ERR "%s: Error decrypting page "
-				       "at index [%ld]; rc = [%d]\n",
-				       __func__, page->index, rc);
-				ClearPageUptodate(page);
-				goto out;
+			if (prev_page_end_size
+			    >= i_size_read(page->mapping->host)) {
+				zero_user(page, 0, PAGE_CACHE_SIZE);
+			} else {
+				rc = ecryptfs_decrypt_page(page);
+				if (rc) {
+					printk(KERN_ERR "%s: Error decrypting "
+					       "page at index [%ld]; "
+					       "rc = [%d]\n",
+					       __func__, page->index, rc);
+					ClearPageUptodate(page);
+					goto out;
+				}
 			}
 			SetPageUptodate(page);
 		}
 	}
-	prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 	/* If creating a page or more of holes, zero them out via truncate.
 	 * Note, this will increase i_size. */
 	if (index != 0) {