which dentry a page belongs to

[Shaya Potter <spotter@cs.columbia.edu>]

I'm trying to do something funky w/ dentry's in a filesystem's
writepage() function.

I know it's easy to figure out which inode a page belongs to as the
address_space structure is tied to it which points to the inode.  

page->mapping->host

and it seems one should be able to figure out which vm_area_struct that
the page belongs to, and from there figure out the correct dentry, but
I'm unsure if this is easy or should work.  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?

thanks,

shaya