Add comments describing what the directions "up" and "down" mean and ref count
handling to the VFS mount following family of functions.
Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx> (Original author)
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/namei.c | 10 ++++++++++
fs/namespace.c | 16 ++++++++++++++--
2 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index a780ea5..4dc0e1d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -688,6 +688,16 @@ static int follow_up_rcu(struct path *path)
return 1;
}
+/*
+ * follow_up - Find the mountpoint of path's vfsmount
+ *
+ * Given a path, find the mountpoint of its source file system.
+ * Replace @path with the path of the mountpoint in the parent mount.
+ * Up is towards /.
+ *
+ * Return 1 if we went up a level and 0 if we were already at the
+ * root.
+ */
int follow_up(struct path *path)
{
struct mount *mnt = real_mount(path->mnt);
diff --git a/fs/namespace.c b/fs/namespace.c
index baedd0b..35c3b80 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -515,8 +515,20 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
}
/*
- * lookup_mnt increments the ref count before returning
- * the vfsmount struct.
+ * lookup_mnt - Return the first child mount mounted at path
+ *
+ * "First" means first mounted chronologically. If you create the
+ * following mounts:
+ *
+ * mount /dev/sda1 /mnt
+ * mount /dev/sda2 /mnt
+ * mount /dev/sda3 /mnt
+ *
+ * Then lookup_mnt() on the base /mnt dentry in the root mount will
+ * return successively the root dentry and vfsmount of /dev/sda1, then
+ * /dev/sda2, then /dev/sda3, then NULL.
+ *
+ * lookup_mnt takes a reference to the found vfsmount.
*/
struct vfsmount *lookup_mnt(struct path *path)
{
--
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