github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-24 23:22:31 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

fs/namespace.c: sanitize descriptions for {__,}lookup_mnt()

Browse Source 
Comments regarding "shadow mounts" were stale - no such thing anymore.
Document the locking requirements for __lookup_mnt().

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-08-20 03:11:30 -04:00
parent fc812c40f5
commit 19ac81735c
1 changed files with 12 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
fs/namespace.c
View File

@ -825,24 +825,16 @@ static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
}
/**
* __lookup_mnt - find first child mount
* __lookup_mnt - mount hash lookup
* @mnt: parent mount
* @dentry: mountpoint
* @dentry: dentry of mountpoint
*
* If @mnt has a child mount @c mounted @dentry find and return it.
* If @mnt has a child mount @c mounted on @dentry find and return it.
* Caller must either hold the spinlock component of @mount_lock or
* hold rcu_read_lock(), sample the seqcount component before the call
* and recheck it afterwards.
*
* Note that the child mount @c need not be unique. There are cases
* where shadow mounts are created. For example, during mount
* propagation when a source mount @mnt whose root got overmounted by a
* mount @o after path lookup but before @namespace_sem could be
* acquired gets copied and propagated. So @mnt gets copied including
* @o. When @mnt is propagated to a destination mount @d that already
* has another mount @n mounted at the same mountpoint then the source
* mount @mnt will be tucked beneath @n, i.e., @n will be mounted on
* @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt
* on @dentry.
*
* Return: The first child of @mnt mounted @dentry or NULL.
* Return: The child of @mnt mounted on @dentry or %NULL.
*/
struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
{
@ -855,21 +847,12 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
return NULL;
}
/*
* lookup_mnt - Return the first child mount mounted at path
/**
* lookup_mnt - Return the child mount mounted at given location
* @path: location in the namespace
*
* "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.
* Acquires and returns a new reference to mount at given location
* or %NULL if nothing is mounted there.
*/
struct vfsmount *lookup_mnt(const struct path *path)
{