[PATCH 1/2] eCryptfs: Write out all dirty pages just before releasing the lower file

[Colin King]

From: Tyler Hicks <tyhicks at canonical.com>

Fixes a regression caused by:

821f749 eCryptfs: Revert to a writethrough cache model

That patch reverted some code (specifically, 32001d6f) that was
necessary to properly handle open() -> mmap() -> close() -> dirty pages
-> munmap(), because the lower file could be closed before the dirty
pages are written out.

Rather than reapplying 32001d6f, this approach is a better way of
ensuring that the lower file is still open in order to handle writing
out the dirty pages. It is called from ecryptfs_release(), while we have
a lock on the lower file pointer, just before the lower file gets the
final fput() and we overwrite the pointer.

BugLink: https://launchpad.net/bugs/1047261

Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
Reported-by: Artemy Tregubenko <me at arty.name>
Tested-by: Artemy Tregubenko <me at arty.name>
Tested-by: Colin Ian King <colin.king at canonical.com>
(upstream cherry pick 7149f2558d5b5b988726662fe58b1c388337805b)
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 fs/ecryptfs/main.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 2768138..9b627c1 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -162,6 +162,7 @@ void ecryptfs_put_lower_file(struct inode *inode)
 	inode_info = ecryptfs_inode_to_private(inode);
 	if (atomic_dec_and_mutex_lock(&inode_info->lower_file_count,
 				      &inode_info->lower_file_mutex)) {
+		filemap_write_and_wait(inode->i_mapping);
 		fput(inode_info->lower_file);
 		inode_info->lower_file = NULL;
 		mutex_unlock(&inode_info->lower_file_mutex);
-- 
1.7.10.4