[06/24] fs: add is_userns_visible() helper

Submitted by Christian Brauner on Feb. 11, 2020, 4:57 p.m.

Details

Message ID 20200211165753.356508-7-christian.brauner@ubuntu.com
State New
Series "user_namespace: introduce fsid mappings"
Headers show

Commit Message

Christian Brauner Feb. 11, 2020, 4:57 p.m.
Introduce a helper which makes it possible to detect fileystems whose
superblock is visible in multiple user namespace. This currently only
means proc and sys. Such filesystems usually have special semantics so their
behavior will not be changed with the introduction of fsid mappings.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 include/linux/fs.h | 5 +++++
 1 file changed, 5 insertions(+)

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diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98e0349adb52..1449cd363fb6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3627,4 +3627,9 @@  static inline int inode_drain_writes(struct inode *inode)
 	return filemap_write_and_wait(inode->i_mapping);
 }
 
+static inline bool is_userns_visible(unsigned long iflags)
+{
+	return (iflags & SB_I_USERNS_VISIBLE);
+}
+
 #endif /* _LINUX_FS_H */