[PATCH v4 2/3] memfd: implement get_id for memfd_luo

[Pasha Tatashin <pasha.tatashin@soleen.com>]

Memfds are identified by their underlying inode. Implement get_id
for memfd_luo to return the inode pointer. This prevents the same
memfd from being managed twice by LUO if the same inode is pointed
by multiple file objects.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 mm/memfd_luo.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
index b8edb9f981d7..6629ab4d8e30 100644
--- a/mm/memfd_luo.c
+++ b/mm/memfd_luo.c
@@ -529,6 +529,11 @@ static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler,
 	return shmem_file(file) && !inode->i_nlink;
 }
 
+static unsigned long memfd_luo_get_id(struct file *file)
+{
+	return (unsigned long)file_inode(file);
+}
+
 static const struct liveupdate_file_ops memfd_luo_file_ops = {
 	.freeze = memfd_luo_freeze,
 	.finish = memfd_luo_finish,
@@ -536,6 +541,7 @@ static const struct liveupdate_file_ops memfd_luo_file_ops = {
 	.preserve = memfd_luo_preserve,
 	.unpreserve = memfd_luo_unpreserve,
 	.can_preserve = memfd_luo_can_preserve,
+	.get_id = memfd_luo_get_id,
 	.owner = THIS_MODULE,
 };
 
-- 
2.43.0