On Tue, 2013-07-09 at 11:33 +0100, David Howells wrote:
> Milosz Tanski <milosz@xxxxxxxxx> wrote:
>
> > It looks like both the cifs and NFS code do not bother with any
> > locking around cifs_fscache_set_inode_cookie. Is there no concern over
> > multiple open() calls racing to create the cookie in those
> > filesystems?
>
> Yeah... That's probably wrong. AFS obviates the need for special locking by
> doing it in afs_iget().
>
> Hmmm... I think I've just spotted what might be the cause of pages getting
> marked PG_fscache whilst belonging to the allocator.
>
> void nfs_fscache_set_inode_cookie(struct inode *inode, struct file *filp)
> {
> if (NFS_FSCACHE(inode)) {
> nfs_fscache_inode_lock(inode);
> if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
> nfs_fscache_disable_inode_cookie(inode);
> else
> nfs_fscache_enable_inode_cookie(inode);
> nfs_fscache_inode_unlock(inode);
> }
> }
>
> can release the cookie whilst reads are in progress on it when an inode being
> read suddenly changes to an inode being written. We need some sort of
> synchronisation on that there.
Change fscache_uncache_all_inode_pages to always take the page lock,
check the value of page->mapping, and wait for outstanding writes to
finish before trying to release PG_fscache?
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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