On Wed, 2010-08-11 at 22:26 -0700, Patrick J. LoPresti wrote: > (Well, crud. I screwed up the previous diff and was missing a > close-curly. This version actually compiles...) > > This patch fixes some coherence bugs in the NFS "dentry lookup cache". > > The NFS dentry lookup cache provides the nfs_force_lookup_revalidate() > call to invalidate all cached dentries associated with an inode. In > general, the NFS client uses the ctime and mtime in the inode to detect > when changes are made on the server. > > Therefore, to maintain cache coherence, nfs_force_lookup_revalidate() > must be called whenever the ctime or mtime of a directory inode is > updated with fresh data from the server. There are a few spots in > nfs_wcc_update_inode() where this rule is violated, making it possible > for the lookup cache to return arbitrarily stale data. > > This actually bit me in practice. I have an application where a > negative dentry results in -ENOENT for a file that was created 30+ > minutes earlier (despite the "noac" mount option). Unfortunately I > cannot share my test case, but I believe the following simple patch is > "obviously correct", and I can confirm that it fixes my issue. This looks less than obviously correct to me. The wcc case is invoked when the ctime/mtime/.... change is known to have occurred due to a file creation/unlink/... from this client. It is a weak cache consistency case. If your client is seeing ENOENT after it created the file itself, then the problem isn't cache coherency, but a bug in the file creation code. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
