[PATCH 13/16] Unionfs: support splice(2)

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

Also remove redundant variable from unionfs_readpage (saves a bit on stack
space).

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/file.c |    1 +
 fs/unionfs/mmap.c |   10 ++++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/unionfs/file.c b/fs/unionfs/file.c
index cfbfb8e..b7d0d55 100644
--- a/fs/unionfs/file.c
+++ b/fs/unionfs/file.c
@@ -246,4 +246,5 @@ struct file_operations unionfs_main_fops = {
 	.fsync		= unionfs_fsync,
 	.fasync		= unionfs_fasync,
 	.splice_read	= generic_file_splice_read,
+	.splice_write	= generic_file_splice_write,
 };
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
index fa358ef..623a913 100644
--- a/fs/unionfs/mmap.c
+++ b/fs/unionfs/mmap.c
@@ -147,7 +147,7 @@ static int unionfs_readpage(struct file *file, struct page *page)
 	struct inode *inode;
 	mm_segment_t old_fs;
 	char *page_data = NULL;
-	loff_t offset;
+	mode_t orig_mode;
 
 	unionfs_read_lock(file->f_path.dentry->d_sb);
 	err = unionfs_file_revalidate(file, false);
@@ -175,11 +175,17 @@ static int unionfs_readpage(struct file *file, struct page *page)
 	 * the necessary magic for us.
 	 */
 	lower_file->f_pos = page_offset(page);
-	offset = page_offset(page);
 	old_fs = get_fs();
 	set_fs(KERNEL_DS);
+	/*
+	 * generic_file_splice_write may call us on a file not opened for
+	 * reading, so temporarily allow reading.
+	 */
+	orig_mode = lower_file->f_mode;
+	lower_file->f_mode |= FMODE_READ;
 	err = vfs_read(lower_file, page_data, PAGE_CACHE_SIZE,
 		       &lower_file->f_pos);
+	lower_file->f_mode = orig_mode;
 	set_fs(old_fs);
 	if (err >= 0 && err < PAGE_CACHE_SIZE)
 		memset(page_data + err, 0, PAGE_CACHE_SIZE - err);
-- 
1.5.2.2