[PATCH v3 6/6] ovl: add ovl_fadvise()

[Amir Goldstein <amir73il@gmail.com>]

Implement stacked fadvise to fix syscalls readahead(2) and fadvise64(2)
on an overlayfs file.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: d1d04ef8572b ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/file.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index a4acd84591d4..42d2d034d85c 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -331,6 +331,23 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 	return ret;
 }
 
+int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+	struct fd real;
+	int ret;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	/* XXX: do we need mounter credentials? */
+	ret = vfs_fadvise(real.file, offset, len, advice);
+
+	fdput(real);
+
+	return ret;
+}
+
 static long ovl_real_ioctl(struct file *file, unsigned int cmd,
 			   unsigned long arg)
 {
@@ -499,6 +516,7 @@ const struct file_operations ovl_file_operations = {
 	.fsync		= ovl_fsync,
 	.mmap		= ovl_mmap,
 	.fallocate	= ovl_fallocate,
+	.fadvise	= ovl_fadvise,
 	.unlocked_ioctl	= ovl_ioctl,
 	.compat_ioctl	= ovl_compat_ioctl,
 
-- 
2.7.4