Re: which dentry a page belongs to

[Jamie Lokier <jamie@shareable.org>]

Shaya Potter wrote:
> It would seem that since the
> address_space object contains the vm_area_struct's of i_mmap and
> i_mmap_shared I should then be able to get the appropriate file and
> dentry object's through
> 
> page->mapping->i_mmap->vm_file->f_dentry
> 
> or
> 
> page->mapping->i_mmap_shared->vm_file->f_dentry
> 
> 1) Is this correct logic?  I'm assuming the only things that matters in
> choosing which list is used if the page is map'd shared or not? is that
> correct as well?

No, no and no.

i_mmap and i_mmap_shared are lists.  They can both be empty, or both
non-empty.  A page can be mapped shared *and* non-shared at the same
time.  A page might not be mapped at all.

Also, a page is often mapped in a _subset_ of the mappings which are
found in i_mmap and i_mmap_shared: it depends on its offset, and the
vma offsets, and non-linear mapping offsets.

It is possible to find multiple dentries which are currently being
used to map a page.

It's also possible to find no dentries at all.

Your question is extremely ill-formed.  What do you mean by "the
dentry corresponding to a page"?  What do you want the value for?

-- Jamie