d_walk() might skip too much

when we find that a child has died while we'd been trying to ascend,
we should go into the first live sibling itself, rather than its sibling.

Off-by-one in question had been introduced in "deal with deadlock in
d_walk()" and the fix needs to be backported to all branches this one
has been backported to.

Cc: stable@vger.kernel.org # 3.2 and later
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/dcache.c b/fs/dcache.c
index 656ce522a218f29850e2415b0a038c8208a5dd52..37b5afdaf6989e211151cc55a7fa656a6addd364 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1239,13 +1239,13 @@ ascend:
                /* might go back up the wrong parent if we have had a rename. */
                if (need_seqretry(&rename_lock, seq))
                        goto rename_retry;
-               next = child->d_child.next;
-               while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
+               /* go into the first sibling still alive */
+               do {
+                       next = child->d_child.next;
                        if (next == &this_parent->d_subdirs)
                                goto ascend;
                        child = list_entry(next, struct dentry, d_child);
-                       next = next->next;
-               }
+               } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
                rcu_read_unlock();
                goto resume;
        }