b=5210

r=phil(actual patch)

A workaround for the crash in ll_unhash_aliases on 2.6.
The 2.6 lookup code is now lockless (thanks to the RCU machinations), which
allows it to race with the unhashing in ll_unhash_aliases. The 2.6 __d_drop
doesn't leave the list head ->pprev in a safe state, so the next pass through
this loop (which tries to re-hash it after we lose the dput race), would crash.
For the record, it looks like the kernel's own d_prune_aliases is broken in
the very same way, except that instead of crashing immediately, it just leaves
the d_hash pointers poisoned for someone else to crash on.

diff --git a/lustre/llite/dcache.c b/lustre/llite/dcache.c
index 7bd2cdc..0bb8b83 100644 (file)
--- a/lustre/llite/dcache.c
+++ b/lustre/llite/dcache.c
@@ -168,6 +168,9 @@ restart:
                                dentry->d_inode);
                         dget_locked(dentry);
                         __d_drop(dentry);
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(2,5,0))
+                        INIT_HLIST_NODE(&dentry->d_hash);
+#endif
                         spin_unlock(&dcache_lock);
                         dput(dentry);
                         goto restart;