[PATCH v2] eCryptfs: write optimization

["Li Wang" <liwang@nudt.edu.cn>]

Hi,
  The new version adds the code to handle short copy issue which may occure
in iov_iter_copy_from_user_atomic(). The idea is to let ecryptfs_write_end() return zero,
therefore, give iov_iter_fault_in_readable() a chance to handle the page fault 
for the current iovec, then restart the copy operation.

Cheers,
Li Wang

Signed-off-by: Li Wang <liwang@nudt.edu.cn>
               Yunchuan Wen <wenyunchuan@kylinos.com.cn>

---
 
fs/ecryptfs/mmap.c |   12 ++++++++++--
1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 6a44148..b3fa499 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -346,7 +346,8 @@ static int ecryptfs_write_begin(struct file *file,
 			if (prev_page_end_size
 			    >= i_size_read(page->mapping->host)) {
 				zero_user(page, 0, PAGE_CACHE_SIZE);
-			} else {
+				SetPageUptodate(page);
+			} else if (len < PAGE_CACHE_SIZE) {
 				rc = ecryptfs_decrypt_page(page);
 				if (rc) {
 					printk(KERN_ERR "%s: Error decrypting "
@@ -356,8 +357,8 @@ static int ecryptfs_write_begin(struct file *file,
 					ClearPageUptodate(page);
 					goto out;
 				}
+				SetPageUptodate(page);
 			}
-			SetPageUptodate(page);
 		}
 	}
 	/* If creating a page or more of holes, zero them out via truncate.
@@ -512,6 +513,13 @@ static int ecryptfs_write_end(struct file *file,
 		}
 		goto out;
 	}
+	if (!PageUptodate(page)) {
+		if (copied < PAGE_CACHE_SIZE) {
+			rc = 0;
+			goto out;
+		}
+		SetPageUptodate(page);
+	}
 	/* Fills in zeros if 'to' goes beyond inode size */
 	rc = fill_zeros_to_end_of_page(page, to);
 	if (rc) {