[PATCH 1/3] vfs: add inode iteration method super_iter_inodes

[Stephen Smalley]

On Thu, Oct 15, 2026 at 5:44 AM Huang Shijie <huangsj at hygon.cn> wrote:
>
> This will be used to replace the explicit sb->s_inodes iteration,
> with the caller supplying a callback function and a private data
> pointer that is passed to the callback along with each inode that is
> iterated.
>
> A single iteration function, super_iter_inodes(), is provided, with
> the iteration mode selected by the INO_ITER_F_UNSAFE flag. The
> INO_ITER_F_REFERENCED flag can additionally restrict the iteration to
> inodes that still have a reference.
>
> Without INO_ITER_F_UNSAFE, the callback is called with a valid,
> unlocked and referenced inode, so any inode operation, including
> blocking operations, is allowed. The iterator is responsible for
> inode lifecycle management, so the callback only needs to implement
> the operation it wants to perform on all inodes.
>
> With INO_ITER_F_UNSAFE set, the inodes are iterated without taking a
> reference and the callback is run in an atomic context that must not
> block. This mode is for internal VFS use only and runs under a RCU
> read lock so that the VFS inode is not freed from under the callback.
> It is needed for operations that require tight control over the state
> of the inodes they operate on.
>
> This mechanism allows the existing sb->s_inodes iteration models to
> be maintained, providing a generic implementation for iterating all
> cached inodes on the superblock.
>
> Signed-off-by: Huang Shijie <huangsj at hygon.cn>

Perhaps SELinux could also use this to replace its own inode walking
logic at the tail of security/selinux/hooks.c:sb_finish_set_opts()?