Re: eCryptfs: Request for review

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

On Fri, 2005-10-21 at 16:44 -0500, Michael Thompson wrote:
> On 10/19/05, Badari Pulavarty <pbadari@gmail.com> wrote:
> > It is telling you that there is already IO in progress on that page.
> > Either you ended up in  __block_write_full_page() twice or called
> > __block_write_full_page() before finishing up end_page_writeback().
> 
> OK, I have narrowed it down to the following: we are in
> ecryptfs_writepage, and do the following:
> lower_page = grab_cache_page(lower_inode->i_mapping, 0);
> where lower_page is the page in the lower filesysetm we want to write to.
> 
> We consistantly panic when, after we do the grab_cache_page(), we have
> a locked page which is set for PageWriteback....
> PageWriteback(lower_page) != 0.
> 
> What I would like to know is how I should proceed when I am in this
> condition. I am not sure if it is acceptable to simply return from the
> function, or if I need to set some flags, or wait on the lock to free
> up. Unfortunately, I haven't been digging around the VFS long enough
> to know what makes sense in this case.

If the lower page can be in a writeback state while the upper page
isn't, don't you have other problems (i.e. things writing to the lower
file outside the knowledge of ecryptfs's stacked framework)?