On Fri, May 01, 2009 at 12:11:12PM -0400, Jeff Mahoney wrote: > 2.6.30-rc3 introduced some sanity checks in the VFS code to avoid NFS > bugs by ensuring that lookup_one_len is always called under i_mutex. > > This patch expands the i_mutex locking to enclose lookup_one_len. This was > always required, but not not enforced in the reiserfs code since it > does locking around the xattr interactions with the xattr_sem. > > This is obvious enough, but it survived an overnight 50 thread ACL test. It's not enough, unfortunately ;-/ It deals with the warning, but it leaves an actual hole in there. Look: what happens if we mount it r/o without that directory and then remount r/w? We get dentry for privroot, hash it (negative at that point), then do actual mkdir, unlock root and modify the ->d_compare() of root to reject lookups on that sucker. Too late - in the meanwhile lookups might very well come and find privroot in dcache. BTW, the way ->d_compare() is done in there is rather dumb - if (q1 == &priv_root->d_name) return -ENOENT; ... would do just as well. Why don't we do that lookup *once* (on ->get_sb(), before anything can come and race with us), and then just keep negative dentry if the directory hadn't been around? And set d_compare() for root immediately after that lookup... I've applied your patch as-is, and unless you have objections to the variant above I'll do that as incremental. Comments? -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
