[PATCH 08/12] Unionfs: copyup only if file is being written to

[Erez Zadok <ezk@cs.sunysb.edu>]

Before, we used to copyup on an open(2) call which used flags implying
writing (O_RDWR, O_WRONLY, O_APPEND).  This meant that a file being opened
for writing, then immediately closed (without actually writing to the file),
will still have been copied up.  Now, we don't copyup such files in ->open,
but defer the copyup till later. [Bug #591].

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/commonfops.c |    4 ++--
 fs/unionfs/file.c       |    1 +
 fs/unionfs/union.h      |    1 +
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/unionfs/commonfops.c b/fs/unionfs/commonfops.c
index 83034c2..b7d3e38 100644
--- a/fs/unionfs/commonfops.c
+++ b/fs/unionfs/commonfops.c
@@ -635,7 +635,7 @@ int unionfs_file_release(struct inode *inode, struct file *file)
 	 * This is important for open-but-unlinked files, as well as mmap
 	 * support.
 	 */
-	err = unionfs_file_revalidate(file, true);
+	err = unionfs_file_revalidate(file, UNIONFS_F(file)->wrote_to_file);
 	if (unlikely(err))
 		goto out;
 	unionfs_check_file(file);
@@ -819,7 +819,7 @@ int unionfs_flush(struct file *file, fl_owner_t id)
 	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
 	unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
 
-	err = unionfs_file_revalidate(file, true);
+	err = unionfs_file_revalidate(file, UNIONFS_F(file)->wrote_to_file);
 	if (unlikely(err))
 		goto out;
 	unionfs_check_file(file);
diff --git a/fs/unionfs/file.c b/fs/unionfs/file.c
index f14b38b..09f594d 100644
--- a/fs/unionfs/file.c
+++ b/fs/unionfs/file.c
@@ -67,6 +67,7 @@ static ssize_t unionfs_write(struct file *file, const char __user *buf,
 					lower_file->f_path.dentry->d_inode);
 		fsstack_copy_attr_times(dentry->d_inode,
 					lower_file->f_path.dentry->d_inode);
+		UNIONFS_F(file)->wrote_to_file = true; /* for delayed copyup */
 		unionfs_check_file(file);
 	}
 
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index 4ca4e76..ab877ee 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -91,6 +91,7 @@ struct unionfs_file_info {
 	struct file **lower_files;
 	int *saved_branch_ids; /* IDs of branches when file was opened */
 	struct vm_operations_struct *lower_vm_ops;
+	bool wrote_to_file;	/* for delayed copyup */
 };
 
 /* unionfs inode data in memory */
-- 
1.5.2.2