[linux-cifs-client] Re: readahead not being thrown away by invalidate_inode_pages in 2.4

[Andrew Morton]

Steve French <smfltc at us.ibm.com> wrote:
>
> In the following snippet of the cifs vfs close file handle code
> (.release vfs operation), I see the code below being executed but I
> don't see it actually invalidating what I expect on 2.4 (in particular
> 2.4.24). The equivalent approach works on 2.6. The intent was that when
> the last instance of a file was closed on this client for the readahead
> data to be discarded by the call to invalidate_inode_pages (in 2.6 this
> is invalidate_remote_inode) so we will be forced to go to the server (ie
> invoke  when the file is reopened for current copies of the data (cifs
> distributed caching token management works best when the file is open,
> and would be hard to monitor properly while the server file has no open
> instances on the client).   Is there a different call in 2.4 that can be
> used to discard the readahead pages in the page cache for this inode,
> invalidate_inode_pages does not seem to work as expected?
> 
> if(list_empty(&(CIFS_I(inode)->openFileList))) {
>   cFYI(1,("closing last open instance for inode %p",inode));
>   /* if the file is not open we do not know if we can cache
>     info on this inode, much less write behind and read ahead */
>        CIFS_I(inode)->clientCanCacheRead = FALSE;
>        CIFS_I(inode)->clientCanCacheAll  = FALSE;
>        invalidate_inode_pages(inode);
> }
> 
> 
> The result of this code not working is that on 2.4 stale file data can
> continue to be given back to the application on the client, even long
> after the file has been opened and closed by the client and opened,
> updated, closed by multiple other clients or directly on the server
> itself.

(Delayed response)

invalidate_inode_pages() is just best-effort.  If pages are currently under
I/O then they will not be invalidated.

You will probably have some success with

	down(i_sem)
	filemap_fdatasync()
	filemap_fdatawait()
	invalidate_inode_pages()
	up(i_sem)