Re: finding 'struct vfsmount' by given 'struct super_block'

From: Andries Brouwer (aeb@veritas.com)
Date: Mon May 08 2000 - 06:50:10 EST


On Mon, May 08, 2000 at 11:47:37AM +0100, Tigran Aivazian wrote:

> how do I find the vfsmount structure by given superblock?
>
> I tried:
>
> mnt = list_entry(&sb->s_mounts, struct vfsmount, mnt_list);
>
> and
>
> mnt = list_entry(&sb->s_mounts, struct vfsmount, mnt_instances);
>
> and they both point to garbage. I think ->mnt_list is expected to be wrong
> as it is headed by vfsmntlist.prev and not by &sb->s_mounts but
> ->mnt_instances should work (judging from add_vfsmnt()), no?

Look at the definition of list_entry in list.h.
If ptr points to the member field of a struct of type type,
then list_entry(ptr, type, member) points at the struct itself.

Now &sb->s_mounts points to the s_mounts field of a struct superblock
and list_entry(&sb->s_mounts, struct superblock, s_mounts)
would give you sb back again.

But if you delete the & then the second version looks better.

Andries

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